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2015 Fall

Materials for electronics and optoelectronic applications away from silicon.

L

Towards Oxide-Based Electronics: growth and applications of oxide thin films and heterost

Transition metal oxides are ideal candidates as functional materials for next generation of electronic and energy devices. This symposium, organized by the MP1308 TO-BE COST Action “Towards Oxide-Based Electronics”, is open to all scientists of the field. It warmly welcomes all contributors and participants, whether they are or are not members of the TO-BE Action. It will focus on the latest progresses in thin films epitaxial growth, on emergent functionalities at oxide interfaces, and on applications of oxides in the fields on nanoelectronics, energy, sensing and actuation.

 

Scope

 

Complex oxides, with wide variety of functional properties, are extraordinarily appealing as new materials to improve responses in existing devices or to develop radically new ones. Quite usually, oxides showing different functionality are extremely similar in terms of crystal structure, permitting the combination of multiple materials with multiple properties in epitaxial heterostructures. The unique properties of oxides, the multiple responses in heterostructures and the possible coupling between various properties can be exploited in devices of relevance in major fields. As examples, we can mention nanoelectronic memory devices, or microelectromechanical systems for microsensors and actuators.

However, the unique properties of oxides are accompanied by an unprecedented complexity that strongly conditions the properties. Very fine control of the films growth is necessary to obtain a particular microstructure and achieve reproducible functional properties. In addition of the relevance of lattice strain on the functional properties, oxygen octahedral distortions in perovskites, oxygen vacancies and cationic defects, chemical termination in surface films and interfaces, and domain walls, can be critical among others. In addition, films, heterostructures and superlattices with orientation different to the (001), offer new opportunities. Recent development on oxide films growth and functional properties including ferroelectricity, mutiferroicity, or resistive switching as well as tunelling devices as those based in ferroelectric barriers and emergent phenomena at oxide interfaces, including two-dimensional electron gases will be presented.

 

Hot topics to be covered by the symposium

 

  • Control of nanostructure in oxide films and influence on properties
  • Real time monitoring of oxide thin films growth
  • Integration of crystalline oxides with silicon
  • Electrical and optical properties of oxide films
  • Ferroic orders in oxide films
  • Interface phenomena in oxide heterostructures
  • Nanoelectronic devices based on epitaxial oxides
  • Oxides as energy materials

 

Tentative list of invited speakers (Partial list. To be confirmed)

 

  • Fabio Miletto-Granozio, CNR-SPIN, Naples, Italy
  • Jean Fompeyrine, IBM, Zurich, Switzerland
  • Jacobo Santamaría, Universidad Complutense, Madrid, Spain
  • Susanne Hoffmann-Eifert, Forschungszentrum Jülich, Germany
  • Josee Kleibeuker, Cambridge University, UK
  • Matjaz Spreitzer, Jozef Stefan Institute, Ljubljana, Slovenia
  • Wilfred Prellier, CRISMAT, Caen, France
  • Michal Sing, Würzburg, Germany
  • Hiroki Kurata, Kyoto University, Japan
  • Di Xiao, Oak Ridge National Laboratory, USA

 

Tentative list of scientific committee members

 

  • Josep Fontcuberta, ICMAB-CSIC, Barcelona, Spain
  • Thomas Schroeder , IHP, Frankfurt (Oder), Germany
  • Luis Morellón, Universidad de Zaragoza, Spain
  • Tamalika Banerjee, University of Groningen, The Netherlands
  • Mark Huijben, University of Twente, Netherlands
  • Salvatore Amoruso, SPIN-CNR, Naples, Italy
  • Nini Pryds, Technical University of Denmark, Denmark
  • María Varela, Universidad Complutense, Madrid, Spain
  • Patrytja Parush, University of Geneve, Switzerland
  • Beatriz Noheda, University of Groningen, The Netherlands
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Towards oxide-based electronics : Florencio Sanchez
09:30
Authors : Fabio Miletto Granozio
Affiliations : CNR-SPIN

Resume : Symposium L is organised by the COST Action MP1308 "Towards oxide-based electronics" (TO-BE), a four-years EU project started in June 2014. The TO-BE Action is open to new participants. It networks nationally- and EU-funded researches active on synthesis, analysis, modelling and applications of transition metal oxides within the European Research Area (ERA), allowing to: define targets, strategies and methods; reduce fragmentation; aggregate communities with complementary know-how; establish a regular know-how transfer with private corporations and other stakeholders; built the future oxide electronics community by fostering the participation of early stage researchers, providing them a suitable training and tackling gender unbalance. The aim of this talk is to briefly describe the structure of the Action, to summarise the activity of the first year, and to try identifying some directions and perspectives for transition-metal oxides science and technology in the next upcoming years.

L.1.1
10:00
Authors : S. Hoffmann-Eifert [1], F. Gunkel [2], R. De Souza [3], R. Dittmann [1], and R. Waser [1,2]
Affiliations : [1] Peter Gruenberg Institut, Forschungszentrum Juelich GmbH, and JARA-FIT, Germany; [2] Institut fuer Werkstoffe der Elektrotechnik II, RWTH Aachen University and JARA-FIT, Germany; [3] Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, Germany

Resume : Understanding the role of defects on the functionalities of complex oxide thin films and heterostructures is decisive for the development of next generation oxide-based electronic and energy devices. Although the influences of defects on the bulk properties of functional oxides are well described by the model of defect chemistry [1] there is still a lack of understanding for thin films and heterostructures. Reasons are for example, that thin film growth is a thermodynamically non-equilibrium process and that surface states and interface charges can lead to additional space charge potentials. This makes the identification of the dominating defects and the description of their influence on the electrical properties of nanostructure oxide devices very difficult. In this talk we will discuss thin film and heterostructure devices derived from SrTiO3, the ‘model material of defect chemistry’. Results of our group are presented which provide a deeper understanding of the role of cationic and anionic type defects on the (1) leakage currents in SrTiO3 thin films and (2) transport properties of LaAlO3/SrTiO3 (LAO/STO) 2DEG heterostructures. For both studies we combined measurements of the equilibrium electrical conductivity as a function of temperature and oxygen partial pressure with growth and transport studies of the devices. Utilizing a defect chemistry thermodynamic model for ultrathin epitaxial SrTiO3 films we could predict the enhanced electronic conductivity quantitatively on the basis of an interface-proximity effect [2]. For LAO/STO 2DEG heterostructures we were able to identify charge compensation mechanisms and decisive defect species [3-5]. In addition, established defect chemistry models of the LAO/STO interface [3] are improved by including local space charges considering the electro-chemical potential not only for electronic charge carriers, but also for all other charged defect species [6]. [1] D. M. Smyth, ‘The defect chemistry of metal oxides’, Oxford University Press Inc., USA (2000) [2] R. De Souza, et al., Phys. Rev. B 89, 241401 (2014) [3] F. Gunkel, et al., Appl. Phys. Lett. 97, 012103 (2010) [4] F. Gunkel, et al., Appl. Phys. Lett. 100, 052103 (2012) [5] F. Gunkel, et al., Nanoscale 7, 1013 (2015) [6] F. Gunkel, et al., Symposium O, O5.3, EMRS Spring Meeting, Lille 2015.

L.1.2
10:30 Coffee break    
 
Emergent properties at interfaces : Gertjan Koster
11:00
Authors : K. S. Takahashi, Y. Matsubara, M. S. Bahramy, Y. Kozuka, D. Maryenko, J. Falson, A. Tsukazaki, Y. Tokura, and M. Kawasaki
Affiliations : RIKEN Center for Emergent Matter Science (CEMS); Tohoku University; University of Tokyo

Resume : Recently, SrTiO3 (STO)-based 2D electron gas systems (2DES) has attracted considerable interest because the 2DES composed of 3d electron bands can be expected to show fascinating quantum properties related to the d orbital nature. Quantum Hall effect (QHE) is one of the most profound phenomena, showing the quantum character of two dimensional (2D) electrons. In this presentation, we report the realization of QHE in delta-doped STO fabricated by unique high temperature gas source MBE growth. At low temperatures, quantized Hall plateaus of low Landau filling factor coincided with minima of longitudinal resistance were clearly observed. Interestingly, the Hall resistance Rxy seems to be quantized at h/e2n with even-integer n. By our band calculation, such peculiar behavior turned out to be strongly related to the band structures confined in the delta-doped STO quantum well. This quantum Hall effect was demonstrated for the first time in d electrons of STO based 2DES.

L.2.1
11:30
Authors : J. Fontcuberta1, M. Isasa2, F. Sanchez1, A. Bedoya-Pinto2, S. Velez2, F. Golmar2, L. E. Hueso2,3 and Felix Casanova
Affiliations : 1 Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC). Campus UAB. 08193 Bellaterra, Catalonia. Spain; 2 CIC nanoGUNE, 20018 Donostia-San Sebastian, Basque Country, Spain; 3 IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Basque Country, Spain

Resume : Spin-orbit coupling is the toggle key that allows manipulating the magnetic ordering by electrical charges and viceversa: for instance, it allows control of ferroelectric polarization by magnetic fields and the magnetic order by electric fields. Spin-orbit interaction is also the source of magnetoresistance in magnetic materials, both antiferromagnetic and ferromagnetic, either metallic or semiconducting [1]. Most interestingly, magnetoresistance is also observed if a non-magnetic metal, having a large spin-orbit coupling, is placed adjacent to a ferromagnetic insulator in bilayer structures. Here we will report on the growth and magnetotransport characterization of ultrathin Pt layers grown on insulating CoFe2O4 layers epitaxially grown on substrates having different crystalline orientation. We will show that a magnetoresistance develops in the Pt layer that is well described by the Spin Hall effect and which is strongly dependent on the crystallographic orientation of the CoFe2O4 layer [2]. We shall discuss the microscopic origin and sensitivity of the observed magnetoresistance of Pt on the atomic termination of the neighboring insulating magnetic layer, the open questions and some perspectives. References [1] I. Fina et al. Nature Comms. 5, 4671 (2014) [2] M. Isasa et al. Appl. Phys. Lett. 105, 142402 (2014)

L.2.2
11:45
Authors : Kinga Lasek, Leszek Gladczuk, Pavlo Aleshkevych and Piotr Przyslupski.
Affiliations : Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, PL 02-668 Warsaw, Poland.

Resume : The perpendicular magnetic anisotropy in cobalt-iron thin films was investigated by means of ferromagnetic resonance technique. We examine the magnetic properties of Au/CoxFe1-x/MgO, Au/CoxFe1-x/Au/MgO and Au/CoxFe1-x/Au/MgO/Au/CoxFe1-x structures, epitaxially grown on Au(111). It was shown that 1ML of Au at the CoxFe1-x/MgO interface enhances the surface anisotropy. The composition of CoxFe1-x thin film was optimized in order to induce the magnetization of Au/CoxFe1-x/Au/MgO structures pointing out-of-plane. The Au/CoxFe1-x/Au/MgO/Au/CoxFe1-x structures were studied in order to examine the influence of MgO barrier thickness on interlayer exchange coupling. The obtained results show that for MgO thickness larger than 1 nm the ferromagnetic layers of the heterostructure behaves independently, indicating that magnetic interaction undergoes only for very thin tunneling barrier.

L.2.3
12:00
Authors : T. Schemme1, O. Kuschel1, T. Nordmann1, O. Feige1, K. Küpper1, F. Bertram2, L. Marnitz3, T. Kuschel3, J. Wollschläger1
Affiliations : 1 Fachbereich Physik, Universität Osnabrück, Germany; 2 DESY, Photon Science, Hamburg, Germany; 3 Center of Spinelectronic Materials and Devices, Physics Department, Bielefeld University, Germany

Resume : Electrons carry both charge and spin. While charge is the property used in electronics in the field of spintronics one attempts to use also the spin to store and process information [1]. Here, one key device is the magneto tunneling junction (MTJ) where two magnetic electrodes are separated by a tunneling barrier [2]. Difficulties arising for Si based devices where spins have to be injected from magnetic contacts in the semiconducting material can be circumvented using the concept of all-oxide devices. Here, one approach is to combine lattice matched materials as, e.g., Fe3O4 (ferrimagnetic halfmetal with 100% spin polarization at the Fermi edge) with MgO (insulator with 8 eV band gap). Our investigations focus on the growth of ultrathin epitaxial Fe3O4(001) films using reactive Molecular Beam Epitaxy (Fe deposition in oxygen atmosphere) on lattice matched substrates as MgO(001) (lattice mismatch +0.3%) and STO(001) (lattice mismatch -7.5%). Structural properties of the films are characterized by Synchrotron Radiation based X-Ray Diffraction (SR-XRD). Growing Fe3O4 films on MgO(001), the film structure follows the relaxation path expected from elasticity theory. However, we observe an unusual strong inverse effect for growth on STO with lateral expansion instead of compression pointing to the formation of domain boundaries. The strain of the films depends on their thickness for both substrates. Furthermore, the strain has large impact on the magnetic properties of Fe3O4 films as determined by Magneto Optical Kerr Effect (MOKE). All Fe3O4 films exhibit in-plane magnetization due to their shape anisotropy with pronounced magnetic in-plane anisotropy due to crystal field effects. On one hand, the Fe3O4/MgO(001) structures show the largest coercive fields in <110> directions as expected from Fe3O4 bulk properties [3]. On the other hand, the largest coercive fields are obtained for the <100> directions for Fe3O4/STO(001) emphasizing again the unusual physical properties of these strained films. These different magnetic properties are verified by Ferro Magnetic Resonance (FMR). Finally, the electronic properties of Fe3O4 based MTJs with MgO barriers are studied. Depending on the post growth treatment we observe a sign change of the TMR effect which may be caused by Mg interdiffusion [4]. [1] S.A. Wolf et al., Science 294 (2001) 1488. [2] S. Yuasa et al., Nature Mater. 3 (2004) 868. [3] T. Schemme et al., Mat. Res. Express 2 (2015) 016101. [4] L. Marnitz et al., AIP Adv. 5 (2015) 047103.

L.2.4
12:15
Authors : L. Qiao,1,2* J. H. Jang,3 D. J. Singh,3 Z. Gai,2 H. Y. Xiao,4 A. Mehta,5 R. K. Vasudevan,2 A. Tselev,2 Z. X. Feng,6 H. Zhou,7 A. Borisevich,3 A. P. Baddorf,2 and M. D. Biegalski2
Affiliations : 1. School of Materials,The University of Manchester,Manchester, M13 9PL, UK 2. Center for Nanophase Materials Sciences, Oak Ridge National Lab, Oak Ridge, TN 37831, USA 3. Materials Science and Technology Division, Oak Ridge National Lab, Oak Ridge, TN 37831, USA 4. School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China, 5. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, Stanford University, CA 94025, USA 6. Chemical Science and Engineering Division, Argonne National Laboratory, Argonne, IL 60439, USA 7. Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA

Resume : Epitaxial strain provides a powerful approach to tune physical properties of materials through rigid compression or extension of their chemical bonds via lattice-mismatch. Although symmetry-mismatch can lead to new physics by stabilizing novel interfacial structures, challenges in obtaining atomic-level structural information as well as lacking of a suitable approach to separate it from the parasitical lattice-mismatch have limited the development of this field. Here we provide unambiguous experimental evidence that the symmetry-mismatch can be strongly controlled by dimensionality and significantly impact the collective electronic and magnetic functionalities in ultra-thin perovskite heterojunctions. Ultra-thin heterostructure of LaCoO3-SrTiO3 offers a unique solution to separate the lattice-mismatch and symmetry-mismatch. State-of-art diffraction and microscopy reveal that symmetry breaking dramatically modifies the interfacial structure of CoO6 octahedral building-blocks, resulting in expanded octahedron volume, reduced covalent screening and stronger electron correlations. Such phenomena fundamentally alter the electronic and magnetic behavior of LaCoO3 thin-films. We conclude that for epitaxial systems, correlation strength can be tuned by changing orbital hybridization, thus affecting the Coulomb repulsion, U, instead of by changing the band structure as the common paradigm in bulks. These results clarify the origin of magnetic ordering for epitaxial LaCoO3 and provide a route to tune electron correlation and magnetic functionality by orbital engineering at oxide heterojunctions.

L.2.5
12:30 Lunch break    
 
Magnetic oxide thin films : Kei Takahashi
14:00
Authors : Kleibeuker J E 1, Choi E-M 1, MacLaren I 2, MacManus-Driscoll J L 1
Affiliations : 1 Materials Science and Metallurgy Department, University of Cambridge, Cambridge, United Kingdom; 2 Materials and Condensed Matter Physics, School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom

Resume : Perovskites oxides are under high attention due to their wide variety of interesting properties and their structure compatibility that allows stacking of different perovskites at the unit cell level. To control and manipulate these perovskite material properties at the atomic level is currently under intensive investigation. In this talk, we will present various magnetic material systems for which interfacial charge transfer is crucial to achieve the observed magnetic behaviour. From charge leakage at BiMnO3/BiFeO3 interfaces [1] and a maximum transfer of 1 electron/Mn from Mn3 to Co3 in La2CoMnO6 double perovskites [2], to a transfer of even above 1 electron/interface unit cell at the LaTiO3/LaFeO3 interface [3]. Depending on the material system, the charge transfer led to an huge increase in the ferromagnetic transition temperature to near or above room temperature (La2CoMnO6 and BiMnO3/BiFeO3 respectively) or to a change in magnetic ground state (LaTiO3/LaFeO3). [1] E-M Choi, J.E. Kleibeuker et al.; submitted [2] J.E. Kleibeuker et al.; In preparation [3] J.E. Kleibeuker et al.; PRL (2014)

L.3.1
14:30
Authors : M. Hoffmann (1,2), Vladislav Borisov (3), Sergey Ostanin (2), Ingrid Mertig (1), W. Hergert (1) and Arthur Ernst (2)
Affiliations : (1) Institute of Physics, Martin Luther University Halle-Wittenberg, Von-Seckendorff-Platz 1, 06120 Halle, Germany (2) Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany (3) Institut für Theoretische Physik, Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany

Resume : The perovskite material SrCoO3 (SCO) in its cubic structure is conducting and might be used as a magnetic electrode in oxide heterostructures. According to available experimental studies, the Curie temperatures (TC) is up to 305 K and a magnetic moment is about 3 muB. These magnetic properties seem strongly influenced by the oxygen content. Here we report a first-principles study of SCO using a self-consistent Green's function method within the density functional theory. Our calculation tools allow to consider randomly distributed defects and to estimate the Curie temperatures with a Monte Carlo simulation (MC). The parameters for the MC simulation were obtained from first-principles. We investigated the electronic structure and the magnetic properties including correlation effects with the GGA+U approach. We used the disordered local moment theory for a realistic description of the magnetic state. In contrast to earlier studies, we used only a small U=4.5 eV which was crucial to get TC comparable with the experiments. With respect to the variation tendency of TC with the oxygen-deficiency, we obtained a good qualitative agreement with the experimental studies - oxygen vacancies reduce TC. We could even improve the agreement, when we considered also small strain effects, since, the oxygen vacancies influence also the cell volume of SCO.

L.3.2
14:45
Authors : Patrizio Graziosi, Alessandro Gambardella, Mirko Prezioso*, Ilaria Bergenti, Alberto Riminucci, Valentin Alek Dediu
Affiliations : CNR-ISMN, Institute for nanostructured materials, v. Gobetti 101, 40129, Bologna (Italy) * Present address: University of California, Santa Barbara, Electrical & Computer Engineering Harold Frank Hall, Santa Barbara, CA 93106-9560

Resume : We propose a model for the consistent interpretation of the transport behaviour of manganese perovskites in both the metallic and insulating regimes. Our approach solves the conflict between transport models, which usually neglect polaronic effects in the metallic phase, and, at the other hand, optical conductivity, angle resolved spectroscopy and neutron scattering measurements, which identified polarons in the metallic phase of manganites down to 6 K. Transport characterizations of epitaxial La0.7Sr0.3MnO3 (LSMO) thin films have been accurately collected. Taking into account polaronic effects allows to achieve the best ever fitting of the transport curves in the whole temperature range. The model is successfully applied also to manganite single crystals of other compositions taking data from literature. The results promote a clear and straightforward quantitative description of the manganites involved in charge transport device applications and promises to describe other oxide systems involving a metal-insulator transition. A new mechanism for the growth of manganites thin films is also proposed, based on atomic resolution imaging of LSMO thin films via STM. It is suggested that non-epitaxial crystalline islands, compatible with LSMO planes different from the one imposed by epitaxy, constitute a proto-perovskite phase as a kinetic intermediate of single-layer growth. P. Graziosi et al. Phys. Rev. B 89, 214411 (2014); A. Gambardella et al. Sci. Rep. 4, 5353 (2014).

L.3.3
15:00
Authors : Paolo Perna (1), Fernando Ajejas (1,2), Davide Maccariello (1,2), Ruben Guerrero (1), Laurence Mechin (3), Stephane Flament (3), Julio Camarero (1,2), Rodolfo Miranda (1,2)
Affiliations : (1) IMDEA-Nanociencia, Madrid, Spain (2) Universidad Autonoma de Madrid, Madrid, Spain (3) GREYC UMR 6072, CNRS, ENSICAEN & Université de Caen Basse-Normandie, France

Resume : Half-metallic planar devices could represent a valuable alternative to the common read heads composed of multilayered metallic structures, making use of magnetic domain walls in tailored magnetic anisotropy systems. We present field and angular dependent room temperature simultaneous measurements of the vectorial Kerr magnetization and magnetoresistance measurements for a detailed study on the magnetic properties, including anisotropy, reversal fields, magnetoresistance and magnetization reversal processes, of half-metallic epitaxial La0.7Sr0.3MnO3 thin films grown onto SrTiO3 substrates with different surface orientations [1]. In general, the magnetic properties of the LSMO films can be interpreted with just the uniaxial term with the anisotropy axis given by the film morphology, whereas the strength of this anisotropy depends on both structure and film thickness. By growing the LSMO films onto vicinal surfaces we are able to engineer specific magnetic anisotropy and consequently the magnetization reversal pathways and low-field magnetoresistance responses [2]. The experimental data show that positive and negative anisotropic magnetoresistance can be obtained by playing with the field-driven magnetization and electrical current direction. [1] J. Appl. Phys. 110, 013919 (2011); New J. Physics 12, 103033 (2010); Rev. Sci. Instrum. 85, 053904 (2014) [2] J. Phys. D: Appl. Phys. 46 202001 (2013); J. Appl. Phys. 112, 013906 (2012); [3] In prep. (2015).

L.3.4
15:15
Authors : Sayani Majumdar, Tomi Elovaara, Hannu Huhtinen,Petriina Paturi
Affiliations : Nanomagnetism and Spintronics Group, Department of Applied Physics,Aalto University School of Science, P.O. Box 15100, FI-00076 Aalto, Finland Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku, Finland. University of Turku Graduate School (UTUGS), University of Turku, FI-20014 Turku, Finland.

Resume : Insulator-to-metal transition (IMT) phenomena in complex oxides are a topic of great scientific and technological interest due to their potential applications in resistive memories. In transition metal oxides, the non-volatile insulator to metal resistive switching is achieved when the strongly correlated electrons of the initial Mott insulator state are released to the conduction band by external stimuli, such as an electric field, magnetic field, pressure or illumination. These phase transitions are quite complex and show interplay of charge, spin, orbital and crystal orderings, not yet completely clarified and hence explored. For technological applications, it is also important to study how efficiently these transitions can be driven from one phase to another. The small bandwidth manganite Pr1−xCaxMnO3 (PCMO), with x = 0.3−0.5, is known for colossal magnetoresistance (CMR), where the drastic reduction of electrical resistance is achieved by applying a sizable electric or magnetic field which melts the insulating charge ordered (CO) phase In this presentation, we will report that by illumination CMR of almost 9 orders of magnitude can be achieved in PCMO (x = 0.4) thin film under 50% less applied magnetic field compared to that in dark. We term this combined effect of light and magnetic field on the sample resistance as magneto-photoresistance (MPR). The result could have significant impact on the new generation of phase-change memories working under affordable conditions.

L.3.5
15:30 Coffee break    
 
Ferroelectric thin films I : Josep Fontcuberta
16:00
Authors : David Hernandez Martin1, Yaohua Liu2, Ana Pérez-Muñoz1, Mariona Cabero 1, J. I. Beltran3, J. Tornos1, G. Sanchez-Santolino1, C. Munuera3, A. Rivera-Calzada1, Maria Varela1, M. C. Muñoz3, F. Mompean3, M. Garcia-Hernandez3, Stephen J. Pennycook4, Carlos Leon1, Suzanne te Velthuis2, Zouhair Sefrioui1, Jacobo Santamaria1
Affiliations : 1 Grupo de Fisica de Materiales Complejos, Universidad Complutense, 28040 Madrid, Spain 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA, 3 2 Instituto de Ciencia de Materiales de Madrid. ICMM CSIC 28049 Cantoblanco 4 Dept. of Materials Science and Engineering, National University of Singapore.117574 Singapore

Resume : Magnetic tunnel junctions with active barriers have focused much interest in recent years due to the possibility of expanding their functionalities by defining multiple resistance states. When a ferroelectric tunnel barrier is sandwiched between two metallic electrodes with different screening lengths the tunneling current is largely controlled by the orientation of the ferroelectric polarization giving rise to the so called tunneling electroresistance defined in terms of the 1-R(up)/R(down). The sign of the electroresistance is determined by the modulation of the barrier height at the interface with the metal with the shortest screening length. Here we discuss the control of the generation and transport of oxygen vacancies at redox active electrodes at epitaxial interfaces to manipulate their electronic structure to design novel functionalities externally controllable by an electric field. This breaks the current paradigm of examining electronic reconstructions in nominally perfect (“power point”) interfaces to make use of the unavoidable defects at interfaces to tailor novel electronic states. We exploit oxygen vacancy transport associated to resistive switching of tunneling barriers of tunnel junctions: Controlling accumulation of oxygen vacancies in the BTO barrier at the LSMO interfaces enables independent variation of the width or the height of the tunnel barrier. This yields a controlled sign change of the electroresistance upon polarization switching. We show that clockwise and counter-clockwise memristors can be tailored on the same sample yielding multiple resistance states. The memristive response resulting from the separate switching of polarization and oxygen vacancies enables the modification of the magnetic state of the LSMO at the interface. Novel forms of charge spin coupling are envisaged allowing for new device concepts based on switchable multiple memory states (spin memristors).

L.4.1
16:30
Authors : Daniel I. Bilc 1, Liviu Zarbo 1, Leontin Padurariu 2, and Liliana Mitoseriu 2
Affiliations : 1 Mol & Biomol Phys Dept, Natl Inst Res & Dev Isotop & Mol Technol, RO-400293 Cluj-Napoca, Romania; 2 Department of Physics, Alexandru I. Cuza University, RO-700506 Iasi, Romania

Resume : Understanding the behaviour of advanced oxide materials under applied finite electric field E is very important both from fundamental and practical application aspects. Many of these oxide materials are composites with different grain sizes designed between prototypical ferroelectric FE (BaTiO3, PbTiO3,...) and dielectric materials, in which E can vary strongly and affect the local structural and FE properties. From these perspectives, we have studied at the first-principles level the structural, electronic, and FE switching properties of typical FE materials within the formalism of finite electric field E [1]. For the case of bulk and FE monodomain in the presence of the large fields, we estimate coercive fields Ec~30 MV/m and switching behaviour in which the electronic polarization rotates between the tetragonal, rhombohedral and orthorombic directions while the local structure is changing according to the direction of polarization. We see at these large fields that the structural parameters change significantly decreasing the strain between the different structural phases and this effect favours a switching mechanism in which the polarization rotates rather than an Ising mechanism, which requires the system to pass through the high symmetry structure (cancelation of polarization). 1. I. Souza, J. Iniguez, D. Vanderbilt, Phys. Rev. Lett. 89, 117602 (2002).

L.4.2
16:45
Authors : Šarūnas Bagdzevičius 1,2, Rūta Mackevičiūtė 1, Maksim Ivanov 1, Barbara Fraygola 2, Nava Setter 2, Jūras Banys 1.
Affiliations : 1 Faculty of Physic, Vilnius University, Sauletekis str. 9/3, LT-10222 Vilnius, Lithuania. 2 Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland.

Resume : The aim of this work was to characterize Pulsed laser deposited epitaxially strained BST70/30 (Ba0.7Sr0.3TiO3) thin films and investigate misfit strain and electrode material effects on functional thin film properties. Thin films were analysed by structural and electrical characterization techniques. BST70/30 thin films were deposited on 001 oriented SrTiO3 single crystal substrates with LSMO (La0.8Sr0.2MnO3) and SRO (SrRuO3) electrodes by pulsed laser deposition with KrF excimer laser (λ=248 nm). BST, LSMO and SRO ceramics were used as the targets. Substrates were etched in buffered HF acid and annealed in oxygen flow at 935°C to get atomically smooth surface. Best quality BST films were obtained at 750–800°C deposition temperature range, with 3 Hz laser repetition rate, 40–42 mJ energies and 0.15 mBar oxygen pressure. Dielectric spectroscopy of BST/LSMO//STO revealed that -1.4% epitaxial misfit strain (measured using x-ray reciprocal space map technique) from lattice mismatch with substrate enhanced ferroelectric phase transition in BST thin film from 310 K (in bulk BST70/30) to 621 K (approximated from Curie-Weiss law for measured dielectric permittivity). Dielectric permittivity can be reduced more than 50%, with approximately 1MV/cm external electric field. Depositing thicker functional BST layer (and changing the lower electrode from LSMO to more conductive SRO) allowed relaxing the misfit strain and tune ferroelectric phase transition temperature closer to ambient.

L.4.3
17:00
Authors : Zhi Wu, Jing Zhou, Wen Chen*, Jie Shen, Chun Lv
Affiliations : State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, P. R. China

Resume : In recent years, PZT thin films have been studied for applications in dynamic random-access memory (DRAM), micro-electro-mechanical systems (MEMS), non-volatile random-access memory (NVRAM), due to their good ferroelectric properties [1-3]. Among these applications, PZT-based devices are used over a wide temperature and frequency range which may deteriorate the ferroelectric properties. In addition, for the PZT thin films, the interface between PZT and bottom electrode has an important influence on the microstructure and ferroelectric properties of PZT thin films. Some oxide electrodes and ferroelectric buffer layers were used to modify the PZT/Pt interface, which can improve ferroelectric due to their similar structures. Therefore, it is very important to study the effects of Ba(Mg1/3Ta2/3)O3 (BMT) buffer layer on the temperature and frequency dependence of the ferroelectric properties of Pb(Zr0.52Ti0.48)O3 (PZT) thin films. In this paper, PZT thin films were prepared on Pt/Ti/SiO2/Si substrates via sol-gel method using BMT thin film as buffer layer. The effects of Ba(Mg1/3Ta2/3)O3 buffer layer on the temperature and frequency dependence of the ferroelectric properties of Pb(Zr0.52Ti0.48)O3 thin films were studied. As the temperature increases, there is a decrease in the remanent polarization for the PZT thin films due to the increase in the degree of disorder. However, the remanent polarization for the PZT/BMT heterostructure increases. BMT buffer layer is a non-ferroelectric material and may induce the domain pinning. As the temperature increases, the effect of domain pinning decreases. As the frequency increases, the remanent polarizations for the PZT thin films and PZT/BMT heterostructure decrease. The contribution of the space charges to the remanent polarization is attenuated with increase of the frequency. References: [1] Roelofs, A.; Schneller, T.; Szot, K.; et al. Nanotechnology, 2003, 14, 250. [2] Trolier-McKinstry, S.; Muralt, P. J. Electroceram., 2004, 12, 7. [3] Scott, J. F. Jpn. J. Appl. Phys., 1999, 38, 2272.

L.4.4
 
Poster session I : F. Sanchez, G. Koster, Y. Chen, V. Craciun
17:30
Authors : Hyeonsu Jeong
Affiliations : Korea Institute of Science and Technology

Resume : Liquid crystals (LCs) are finding increasing applications in a wide variety of fields including liquid-crystal display technology, materials science, bioscience, etc. One of the most important issues for using LCs in a range of applications is the ability of the LCs to hold a stable and uniform orientation on a macroscopic scale. In order to achieve a macroscopic ordering in a certain direction, a command layer or so called alignment layer is usually needed. The most common aligning layer is made of polymers and has an anisotropy, which is achievable with several known methods. Here, a new type of LC alignment method without employing polymers is introduced. We describe a novel method for alignment from thermotropic to lyotropic LCs using nano-patterns of electrically conductive indium-tin-oxide (ITO) layers with high resolution (ca < 20nm) and high aspect ratio (ca. 8), fabricated by the second sputtering lithography (SSL). The patterned ITO is found to function as an electrode and alignment layer at the same time, which facilitates successful fabrication of bifunctional conductive alignment layer for LC devices. The LC cells fabricated using patterned ITO substrates show highly stable alignment of LCs over large area and good electro-optical responses. Moreover, systematic approach made by the precise control of pattern dimensions allows us to estimate a critical anchoring energy required for an effective LC alignment based on Berremans’ theory.

L.L I.1
17:30
Authors : Yunzhong Chen1, F. Trier1, T. Wijnands2, R. J. Green3, N. Gauquelin4, R. Egoavil4, D. V. Christensen1, G. Koster2, M. Huijben2, N. Bovet5, S. Macke3, F. He6, R. Sutarto6, J. A. Sulpizio7, M. Honig7, G. E. D. K. Prawiroatmodjo8, T. S. Jespersen8, S. Linderoth1, S. Ilani7, J. Verbeeck4, G. Van Tendeloo4, G. Rijnders2, G. A. Sawatzky3 and N. Pryds1
Affiliations : 1 Department of Energy Conversion and Storage, Technical University of Denmark, Risoe Campus, 4000 Roskilde, Denmark 2 Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands 3 Quantum Matter Institute, Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada. 4 EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium. 5 Nano-Science Center, Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark 6 Canadian Light Source, University of Saskatchewan, Saskatoon, SK S7N2V3, Canada. 7 Department of Condensed Matter Physics, Weizmann Institute of Science, 76100, Rehovot, Israel. 8 Center for Quantum devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark

Resume : The discovery of two-dimensional electron gases (2DEGs) at the interface between two insulating complex oxides, such as LaAlO3 or gamma-Al2O3 epitaxially grown on SrTiO3, provides an opportunity for developing all-oxide electronic devices.However, large enhancement of the interfacial electron mobility remains a major and long-standing challenge for fundamental as well as applied research of complex oxides. Here, we inserted a single unit cell insulating layer of polar La1-xSrxMnO3 (x=0, 1/8, and 1/3) at the interface between disordered LaAlO3 and crystalline SrTiO3 created at room temperature. We find that the electron mobility of the interfacial 2DEG is enhanced by more than two orders of magnitude. Our in-situ and resonant x-ray spectroscopic in addition to transmission electron microscopy results indicate that the manganite layer undergoes unambiguous electronic reconstruction and leads to modulation doping of such atomically engineered complex oxide heterointerfaces [1]. Moreover, the manganite spacer suppresses significantly the formation of oxygen vacancies on the STO side by preventing the interfacial redox reaction, which underlies the key to achieve the pure electronic reconstruction at the buffered interface. At low temperatures, the modulation-doped 2DEG exhibits clear Shubnikov-de Haas oscillations and the initial manifestation of the quantum Hall effect. Reference: [1] Y.Z. Chen et al. Nature Mater. DOI:10.1038/NMAT4303.

L.L I.2
17:30
Authors : Patrik Ščajev1, Ramūnas Nedzinskas1, Saulius Tumėnas1, Andrius Rimkus1, Evelina Pozingytė1, Simona Paurazaitė1, Saulius Miasojedovas2, Laima Trinkler3, Baiba Berzina3, Valdis Korsaks3, Chenlong L. Chen4, Liuwen W. Chang4, Mitch M.C. Chou4
Affiliations : 1Optoelectronics department, Center for Physical Sciences and Technology, A. Goštauto 11, Vilnius, Lithuania 2Institute of Applied Research, Vilnius University, Saulėtekio Ave. 9 - III, Vilnius 10222, Lithuania 3Institute of Solid State Physics, University of Latvia, Kengaraga 8, 1063 Riga, Latvia 4Department of Materials and Optoelectronic Science, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC

Resume : Photoluminescence (PL), temporally- resolved PL (TRPL) and differential reflectivity (DR) techniques were applied for study of carrier recombination in five stacked ZnO/ZnMgO coupled quantum wells (QWs), grown on nonpolar lattice-matched (100) LiGaO2 substrate. For carrier excitation in ZnO wells 266 nm wavelength was used. Polarized PL measurements were performed using monochromator and lock-in amplifier, TRPL was detected by a streak camera and a monochromator, while in DR measurements refractive index changes in the topmost part of the sample (~40 nm) was probed by 1064 nm pulses. The polarized PL emission from QWs, observed at 330 nm, provided temperature-independent depolarisation ratio of ~30%, latter was twice higher at lowest excitations, indicating impact of excitons. The PL intensity was quenched by temperature (few times) and at lowest excitations by defects (emitting at ~450 nm). At higher excitations PL intensity increased linearly on excitation, while PL spectra blue-shifted, indicating for filling of higher QW states and degeneracy, which was confirmed by faster TRPL decays (70-240 ps). The DR measurements also provided fast (~100 ps) decays in QWs, with amplitude linearly increasing with excitation. The observed saturating defect-related component decayed with 2-5 ns time. The variation of temperature in 80-500 K range did not substantially influence the decays. The research was supported by grants: TAP-LLT-02/2014, LLT-14-07, MOST 103-2923-M-110-001-MY3.

L.L I.3
17:30
Authors : Nikola I. Ilić, Bojan S. Stojadinović, Jelena D. Bobić, Nikola Tasić, Zorana D. Dohčević-Mitrović, Biljana D. Stojanović
Affiliations : Institute for Multidisciplinary Research, University of Belgrade, Belgrade, Serbia; Institute of Physics, University of Belgrade, Belgrade, Serbia

Resume : Bismuth ferrite (BiFeO3) attracts huge attention thanks to very distinctive electrical and magnetic properties it possesses. There are several obstacles preventing BiFeO3 ceramic materials in exhibiting these properties: structural instability, occurrence of leakage currents, low density, weakly expressed magnetic properties. Different rules existing in nanosized materials imply that in two-dimensional materials many, if not all, of mentioned problems could be overcome. BiFeO3 thin films were deposited by chemical solution deposition (CSD) method. Precursor solutions were made by dissolving Bi and Fe(III) nitrates in different organic solvents. They were spin-coated on silicon and Si/SiO2/TiO2/Pt(111) substrates, dried and annealed at different temperatures. This way obtained thin films were characterized by XRD, SEM and ellipsometry techniques. Ferroelectric measurements were also performed.

L.L I.4
17:30
Authors : A.I.Savchuk1, I.D.Stolyarchuk1,3, S.A. Savchuk1, I.Stefaniuk2, I. Rogalska2, A. Dzidiecz2, E. Sheregii2.
Affiliations : 1Department of Physics of Semiconductors and Nanostructures, Chernivtsi National University, 2 Kotsyubynsky Str., 58012 Chernivtsi, Ukraine 2Centre for Innovation and Transfer of Natural Sciences and Engineering Knowledge, University of Rzeszow, 16a Rejtana Street, 35959 Rzeszow, Poland 3Department of Physics of Nanostructures and Nanotechnology, Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Krakow, Poland

Resume : Zinc oxide (ZnO) based materials demonstrate attractive properties for different modern technological applications. Doping of ZnO with transition metal (TM) elements offers an effective method to adjust its electrical, optical, and magnetic properties, which is crucial for its practical applications. The present work is devoted to preparing of Zn1-xMexO (Me:Ni,Co) thin films by RF-plasma sputtering technique and study of their structural, optical and magnetic properties depending on content of TM elements. The content x in the deposited films was varied in range of (0 – 0.1). The structures of the samples have been studied by using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The structure and surface morphology of the deposited layers show strong dependence on doping with TM and deposition conditions. The optical absorption spectra of the films demonstrate that the energy bang gap was found to decrease with increase of Co content and complex dependence on the content of Ni. The EPR spectra show a broad asymmetrical line of Dysonian shape and satisfactory ascribed by the single Lorenz type curve with Dysonian term. Near the ferromagnetic ordering temperature distortion of the EPR spectra and its following splitting on two Dysonian lines were found

L.L I.5
17:30
Authors : J. Ventura, M.C. Polo, C. Ferrater, S. Hern?ndez1, J. Sancho-Parram?n2, L.E. Coy3, L. Rodr?guez, A. Canillas, M. Varela
Affiliations : Departament de F?sica Aplicada i ?ptica, Universitat de Barcelona, Spain; 1 Departament d?Electr?nica, Universitat de Barcelona, Spain; 2 Ruđer Bo?ković Institute, Bijenička 54, Zagreb 1000, Croatia 3 NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznan, Poland;

Resume : The isovalent substitution of Ti4 by Zr4 of BaZrxTi1-xO3 (BZT) modifies the dielectric character of ferroelectric BaTiO3 yielding relaxor behaviour. The dynamic coupling between BaTiO3 polar nanoregions and BaZrO3 nonpolar ones is thought to be the responsible mechanism. However, these short-range compositional variations are elusive to detect and this topic is thus rarely addressed. This work demonstrates that titanium and zirconium B-site cations are heterogeneously distributed and, as a consequence, polar nanoregions do exist in BZT. We have grown 100 nm thick stoichiometric BZT thin films with Zr/Ti ratios ranging from x=0 to x=1 on (001)-oriented SrTiO3 substrates by pulsed laser deposition. The structural characterization by X-ray diffractometry showed that a solid solution with fully relaxed single cube-on-cube epitaxial domains was formed across the entire compositional range. The unit cell volume followed a linear relationship with the Zr content, suggesting a proper intermixing of Zr and Ti into an average BZT lattice. Raman activity at room temperature was detected for all the compositions using a UV radiation source. The recorded spectra showed the remanence of ferroelectric BaTiO3 modes along with a decrease of polarizability for increasing Zr content. These facts indicated a disruption of the long range order of BaTiO3 ferroelectricity by the formation of a heterogeneous distribution of Ti and Zr-rich clusters or the existence of local phase segregation. The dielectric permittivity at VIS-UV frequencies (2 to 5 eV) was obtained from spectroscopic ellipsometry measurements, which allowed the band gap energy to be calculated. Strongly asymmetric nonparabolic dependence of band gap energy with composition provided further evidences of nonideal solid solution behaviour with inherent tendency to phase segregation.

L.L I.7
17:30
Authors : Sumin Choi, Cuong Ton-That, Matthew R. Phillips, Igor Aharonovich
Affiliations : University of Technology, Sydney

Resume : Single photon sources (SPSs) that generate non-classical states of light are very important for photonics and emerging quantum technologies. In this regard, zinc oxide (ZnO) has attracted significant attention for its extensive quantum photonic applications in the ultraviolet and visible spectral range because of its highly efficient optical emission. In this work, we study single photon emission and electrically driven light emission from localized defects in ZnO nanoparticles and thin films. Single photon emission characteristics were investigated at room temperature under ambient conditions using scanning confocal microscopy under optical excitation. The emitters exhibit bright broadband fluorescence in the red spectral range at 640 nm with polarized excitation and emission. The quantum emitter is likely to be a charged defect such as a zinc vacancy. With the need to integrate SPSs with scalable photonic devices, efficient electrically driven light emission from localized defects in n-ZnO/p-Si heterojunctions was fabricated using ZnO nanoparticles and thin films. The devices show defect-related electroluminescence at the red spectral range and excellent rectifying behavior. The emission is stable over an extensive period of time, providing an important prerequisite for practical devices. Our results will be important for the realization of cost efficient fabrication of electrically driven, quantum nanophotonic devices employing ZnO as the fundamental building block.

L.L I.8
17:30
Authors : Maciej Krzywiecki1,2, Lucyna Grządziel2, Monika Kwoka3, Adnan Sarfraz1, Andreas Erbe1
Affiliations : 1 Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237 Düsseldorf, Germany 2 Institute of Physics – CSE, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland. 3 Institute of Electronics, Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland

Resume : During the last few years one can observe an increasing interest in electronic devices utilizing hybrid inorganic-organic materials due to their vast range of potential applications (like solar cells, transistors or sensors) and relatively low cost of production. The performance of synthesized hybrid – based electronic devices is tightly linked to the relative energy level alignment of its constituents. The alignment is, in turn, governed by the chemical and structural composition of the interfacial area. In the present work we show hybrid layer systems based on tin dioxide (SnO2), a wide-band gap material of n-type conductivity and copper phthalocyanine, a p-type organic semiconductor of high chemical stability and durability. SnO2 thin films were prepared by a sol-gel process followed by spin-coating, or by the rheotaxial growth and vacuum oxidation method. The organic CuPc ultra-thin (up to 70 Å) overlayers were deposited by physical vapour deposition. Detailed characterization of the prepared hybrid junctions is presented, including a determination of the chemical composition and electronic structure by angle-resolved photoelectron spectroscopy. The optical properties and global electronic properties were determined by spectroscopic ellipsometry. The prepared hybrid systems are suitable for application in hybrid electronics technologies.

L.L I.9
17:30
Authors : A. Apostoluk1, Y. Zhu1, A. Valette2, P. Gautier2, K. Znajdek3, M. Sibinski3, J.-J. Delaunay4, B. Masenelli1, S. Daniele2
Affiliations : 1 Université de Lyon, F-69000 Lyon, France and INL, CNRS, UMR 5270, INSA Lyon, F-69621 Villeurbanne, France; 2 Université de Lyon, F-69000 Lyon, France and IRCELyon, CNRS, UMR 5256, F-69626 Villeurbanne, France; 3 Department of Optoelectronics and Semiconductor Devices, Lodz University of Technology, Poland; 4 School of Engineering, The University of Tokyo, Tokyo, Japan

Resume : Zinc oxide nanoparticles (NPs) have aroused an increasing interest for their potential application in the white light sources and as energy conversion material due to the variety of intrinsic defects which permit to generate a wide emission spectrum from the blue to the IR range. However, the origin of these emissions remains still unclear and the precise control of the defects quantity is a challenging task. Because of the easy and adjustable synthesis condition, sol-gel methods have been applied to synthesize ZnO NPs. The nanoparticle size, morphology, crystalline quality and the zeta potential have been controlled via the modification of the synthesis parameters (the nature of solvent, the presence of the additives and of the surfactants and the reaction time). Since all these synthesis parameters play a major role in the introduction of defects into the structure of ZnO NPs, the defect emission spectrum range and the luminescent efficiency can be controlled. The intense visible emission with a luminescent external quantum efficiency (EQE) of more than 50 % (and up to 70 %) was attained by controlling the crystalline order of ZnO NPs. The hydroxyl group present on the surface of the ZnO NPs turned out to influence their crystalline quality and dispersibility. The influence of ZnO NPs used as energy down-shifting layer on the efficiency of various types of solar cells is also presented.

L.L I.10
17:30
Authors : Virt I., Bester M, Gamernyk R*. Pavlovskyy Y. **, Hadzaman I. **
Affiliations : University of Rzeszow, Rzeszow, Poland *Ivan Franko National University of Lviv, Ukraine **Drogobych State Pedagogical University, Drogobych, Ukraine

Resume : Zinc oxide is an inorganic compound often called a II-VI semiconductor. It is a perspective material for formation of transparent electrodes in systems of display and a different sort sensor controls. The especial attention is given research of a thin film material and structures on their basis, is especial doped magnetic impurity [1]. In the given work results of experimental researches physical properties thin films of ZnO are submitted. A film were deposited by a method of ablation targets Zn1-хCoхO (x ≈ 0,04-0,20) using the pulse laser. The targets are received by consecutive pressing and sintering powder ZnO with additive Co. For removal of a material of a target (process ablation) are used laser YAG:Nd (λ = 1064 nm, f = 0,5 Hz, duration of a pulse of 10 ns [2]). Thin a film deposited on glass and Al2O3 substrates at various temperatures (mainly 30-200 °С) and at various operating modes of the laser. Thin a film were characterized enough by good morphology of a surface. Rather high specific conductivity films small thickness (less than 100 nm) and slow growth is marked at the big thickness. It specifies prevailing process of condensation of atoms metal components (increase in factor of sticking), most likely atoms Zn, at initial stages of growth of a film [3]. Influence on photoconductivity (PC) as grown films have as well the radiating defects caused by laser plasma. Process annealing such radiating defects passes at room temperature within several hours. On research of electric characteristics (in particular, temperature dependences of rise time PC is specified) concentration of carriers is appreciated. Correlation between thickness films and photoconductivity parameters is established. References [1]. Ozgur U., Alivov Ya.I., Liu C., Teke A., Reshchikov M.A., Doğan S., Avrutin V., Cho S.-J., Morkoc H. J. Appl. Phys (2005). v. 98, p. 041301–041310. [2]. Wisz G., Virt I., Kuzma M. Thin Solid Films (1998), v. 336, p. 188–190. [3]. Virt I.S., Hadzaman I.V., Bilyk I.S., Rudyi I.O., Kurilo I.V., Frugynskyi M.S., Potera P. Acta Physica Polonica, (2010), v. 117, p. 34–37.

L.L I.11
17:30
Authors : W. Olszewski 1,2, K. Rećko 2, U. Wykowska 3, C. Marini 1, G. André 4, D. Satuła 2, M. Biernacka 2
Affiliations : 1) ALBA Synchrotron Light Source, Ctra. BP 1413 km. 3,3, 08290 Cerdanyola del Valles, Barcelona, Spain; 2) Faculty of Physics, University of Bialystok, ul. K. Ciołkowskiego 1L, 15-245 Białystok, Poland; 3) Institute of Chemistry, University of Bialystok, ul. K. Ciołkowskiego 1K, 15-245 Białystok, Poland; 4) Laboratoire Leon Brillouin, Bât 563 CEA-Saclay, 91191 Gif sur Yvette Cedex, France

Resume : In the past decade GaFeO3 (GFO) has been intensively studied for its potential applications as a magnetoelectric material [1] and promising memory media which allow a simultaneous reading and writing a data [2]. The physical properties, especially magnetism in GFO, depend strongly on the method of preparation. It forms a collinear antiferromagnetic ordering along [001] direction [3]. Any disorder of the cation origin leads to non-collinear structures, such as ferromagnetic [4], canted antiferromagnetic [5] or ferromagnetic [6]. Therefore many efforts have been expended on fabrication of GFO by Pechini modification of the sol-gel method. Careful preparation gives the ability to systematically track conditions conducive to filling each crystalline sublattice occupancy. In the present study a systematic investigation has been conducted on the multiferroic GFO samples synthesized in three different scenarios, by changing the initial semi-products and heating procedures. Obtained in this way different disorder in site occupancies was probed by synchrotron-based EXAFS technique both at Ga and Fe K-edges over a wide temperature range: 77 - 400 K. [1] R. Saha et al., Solid State Commun. 152 (2012) 1964 [2] D. Stoeffler, J. Phys.: Condens. Matter 24 (2012) 185502 [3] M.J. Han et al., Phys. Rev. B 75 (2007) 060404 [4] J.P. Remeika, J. Appl. Phys. Suppl. 31 (1960) 263S [5] G.T. Rado, Phys. Rev. Lett. 13 (1964) 335 [6] R.B. Frankel et al., Phys. Rev. Lett. 15 (1965) 958

L.L I.12
17:30
Authors : A. Gómez-Núñez, P. Roura, C. López, A. Vilà
Affiliations : Department of Electronics, University of Barcelona, Martí i Franquès 1, E-08028-Barcelona, Spain. ; Department of Physics, University of Girona, Campus Montilivi, Edif. PII, E-17071-Girona, Spain. ; Departament of Inorganic Chemistry, University of Barcelona, Martí i Franquès 1. E-08028-Barcelona, Spain. ; Department of Electronics, University of Barcelona, Martí i Franquès 1, E-08028-Barcelona, Spain.

Resume : ZnO is widely used as n-type semiconducting material because of its low cost combined with excellent electronic properties. It can be easily nanostructured using scalable processing methods based on chemical routes, such as sol-gel. However, stabilization of the metal organic precursors in solvents is one of the main problems in printed electronics, and thermal treatment of printed inks to get the final material is one of the most important issues. The usual sol-gel process to obtain ZnO is based on the use of zinc acetate as a salt and ethanolamine as a stabilizer. Nevertheless, recent studies have demonstrated the non-innocent role of ethanolamine in the precursor decomposition. In this context, thermally induced-reaction mechanisms and their correct interpretation are strongly dependent on the characterization of the evolved species. When the nature of volatile products released by a substance under heating is online determined, e.g. by evolved gas analysis, the results allow describing the reactions taking place. In this work, the processes involved in the thermal decomposition of some precursors have been analysed by thermo-analytical and structural techniques as well as with evolved gas analyses. With the aim of studying the role of the molecular architecture of the stabilizer in the decomposition process, several amino-alcohols have been tested as stabilizer. The obtained results indicate that keeping tabs on the use of ethanolamine as stabilizer is worthwhile.

L.L I.13
17:30
Authors : I.V.Markevich, T.R.Stara
Affiliations : V. Lashkaryov Institute of semiconductor physics of NASU, 41 pr. Nauki, 03028 Kyiv, Ukraine

Resume : Photoluminescence (PL) spectra in undoped Zn1-xMg xO ceramics with x = 0 - 0.20 were investigated at room temperature using Xe-lamp light passing through grating monochromator as exciting source. The samples were sintered at 1000oC in air as well as in Zn vapor. PL spectra of ceramics with x = 0 were shown to consist of green (515 nm), orange (610 nm) and red (720 nm) self-activated bands as well as green band at 540 nm related to residual Cu impurity. In PL spectra of the samples sintered in Zn vapor, self-activated green band was dominant. Under increasing Mg content, side by side with expansion of ZnO bandgap, gradual blueshift of self-activated green band from 515 to 485 nm was observed, whereas the positions of orange and red bands remained unchanged. The origin of emission centers and the cause of their different reaction to the expansion of bandgap are discussed.

L.L I.14
17:30
Authors : Aleksandras Iljinas, Vytautas Stankus, Liutauras Marcinauskas
Affiliations : Department of Physics, Kaunas University of Technology, Studentu str. 50, LT-51368 Kaunas, Lithuania.

Resume : High quality bismuth ferrite thin films were deposited using in situ layer-by-layer reactive direct current magnetron sputtering. The optimal parameters were found in order to achieve the best structural quality of perovskite thin films without post annealing. Films were deposited on platinized silicon (Pt/Ti/SiO2/Si) substrates at 400-600 C temperatures using Ti2O seed layer. It was shown that microstructure strongly depends on deposition temperature. The all deposited thin films formed at 450-550 oC deposition temperature have dense columnar structure and flat surface. Structural, morphological and ferroelectrical properties of thin films were investigated. Hysteresis measurements show that films exhibit ferroelectric properties with maximum coercive field of Ec=210 kV/cm and of Pr=115 mikroC/cm2. It was shown that ferroelectric properties are very sensitive to stoichiometry of thin films. Coercive field dependence on frequency measurements shows that two regimes of domain wall motion are presents.

L.L I.15
17:30
Authors : Stéphane Brochen (1,2,3), Guy Feuillet (1,3) and Julien Pernot (1,2,4)
Affiliations : 1 Univ. Grenoble Alpes, F-38000 Grenoble, France 2 CNRS, Inst NEEL, F-38042 Grenoble, France 3 CEA, LETI, Minatec Campus, F-38054 Grenoble, France 4 Institut Universitaire de France, 103 boulevard Saint-Michel, F-75005 Paris, France

Resume : In this work, statistical formulations, of the temperature dependence of ionized and neutral impurity concentrations in a semiconductor, have been developed in order to elucidate a confusing situation, appearing when compensating acceptor (donor) levels are located sufficiently close to the conduction (valence) band to be thermally ionized and thereby to emit (capture) an electron to (from) the conduction (valence) band. Indeed, these formulations have been used in a parallel description of the carrier concentration and mobility, as a function of the temperature. Therewith, Hall effect and resistivity measurements have been performed on bulk ZnO single crystal, in an attempt to distinguish the presence of a deep acceptor or a deep donor level, coexisting with a shallower donor level and located near the conduction band. Thereby, we have highlighted that an emission of an electron in the conduction band, generally assigned to a (0/+1) donor transition from a donor level, cannot be applied systematically and could also be attributed to a (−1/0) donor transition from an acceptor level. More generally, this result can be extended for any semiconductor and also for deep donor levels located close to the valence band (acceptor transition). [J. Appl. Phys. 115, 163706 (2014)]

L.L I.16
17:30
Authors : E. PEKSU, H. KARAAGAC
Affiliations : Department of Physics, Istanbul Technical University; Department of Physics, Istanbul Technical University

Resume : In recent years, there has been an increasing interest in aluminum doped zinc oxide (AZO) thin films that can be employed for a wide range of applications including solar cells, gas sensor, light-emitting diodes (LEDs), thin film transistors, and photodetectors due to their unique physical and chemical properties .Although indium-doped tin oxide (ITO) films provide perfect electrical and optical properties for transparent conductor applications , the resource availability of indium limits its wide use for large-scale opto-electronic device applications. In this regard, AZO is regarded as one of the best alternative to replace ITO for developing high quality transparent conductive oxide (TCO) films that can be obtained at lower cost. The current study involves the deposition of ZnO and AZO thin films on wide variety of substrates, such as soda-lime glass (SLG), silicon (Si), ITO, Al2O3, and quartz, by using sol-gel deposition technique for the realization of obtaining high quality TCO material at relatively much lower cost. To investigate the effect of Al doping concentration on structural, electrical, and optical properties of ZnO thin films, they were doped with Al for different Al/Zn atomic ratios. X- ray diffraction (XRD), ultraviolet–visible spectroscopy (UV-Vis), and atomic force microscopy (AFM) measurements were performed for the investigation of respective structural, optical and morphological surface properties of the depsosited thin films Results revealed that the best quality of film was obtained for the 1% Al doped ZnO thin film in terms of low-resistivity, high-transmittance and the degree of crystallinity. From the XRD study it was found that all the deposited films have hexagonal crystal structure with a strong preferential orientation in the (0 0 2) plane direction. The transmition measurements showed that the average transmittance was as high as 85-95 % in the 350-1100nm wavelength range and the optic band gap was broadening with increasing doping concentration. The dependence of electrical characteristics on aluminum concentration (1%-5%) in the films was investigated by four-point probe, which revealed that 1% Al-doped ZnO thin film exhibited a relatively lower electrical resistivity compared with other Al/Zn % ratios. AFM measurements indicated that there was a significant modification in the surface morphology following the doping the ZnO thin films with different Al-doping concentrations. In addition to the characteriazation of deposited ZnO and AZO thin films, in this investigation, thin films were also used as seed layer for the growth of ZnO nanowires (NWs), which were employed for the fabrication of SLG/AZO/ZnO-NWs/PCBM structured hybrid solar cell.

L.L I.17
17:30
Authors : Michał A. Borysiewicz1, Monika Masłyk1,2, Marek Wzorek1, Krystyna Gołaszewska1, Renata Kruszka1, Karolina D. Pągowska1, Marcin Myśliwiec1,2 and Eliana Kamińska1
Affiliations : 1 Instytut Technologii Elektronowej, al. Lotników 32/46, 02-668 Warsaw, Poland; 2 Institute of Microelectronics and Optoelectronics of Warsaw University of Technology, ul. Koszykowa 75, 00-662 Warsaw, Poland

Resume : This communication reports on the application of a ZnMgO:Al thin film as a transparent electrode for the p-GaN layer of a GaN-based UV LED emitting at 385 nm. The ZnMgO:Al films are grown by room temperature cosputtering using ZnO:Al and Mg targets. The ZnMgO:Al film is characterized by a unique, heavily disoriented microstructure with Mg clusters. Optical transmission measurements, RBS data and TEM image analysis enabled us to prove that in these films not all of Mg enters the Zn sublattice causing band gap engineering. Instead, some 8 to 9 at. % of Mg atoms form nanoscale Mg clusters in the film influencing the optical and electrical properties of ZnMgO:Al. It is argued by comparison with ZnMgO films grown in the same chamber without Al doping, that Al2O3 precipitates may drive the formation of the Mg clusters and the disorientation of ZnMgO by crystalline frustration. Selected ZnMgO:Al films exhibited a low absorption edge at 341 nm, high UV transparency and sheet resistivity of 30 Ω/□, and were tested as a transparent electrode do p-GaN in the full LED structure. A 2.5-fold increase in irradiated power, compared to standard Ni/Au ohmic contact was achieved with the nanostructured ZnMgO:Al. This research was in part supported by the Institute of Electron Technology statutory activities and in part by the European Union within European Regional Development Fund, through Innovative Economy grant POIG.01.03.01-00-159/08 "InTechFun".

L.L I.18
17:30
Authors : J. P. B. Silva1,2, K. Kamakshi1,2, K. C. Sekhar1, E. C. Queirós3, J. Agostinho Moreira2, A. Almeida2, M. Pereira1, P. B. Tavares3 and M. J. M. Gomes1
Affiliations : 1Centre of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; 2IFIMUP and IN-Institute of Nanoscience and Nanotechnology, Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto, Portugal; 3Centro de Química, Universidade de Trás-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal

Resume : Recently, the ceramics based on solid solutions of ((1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 have emerged as potential materials, that could successfully substitute lead based piezoelectric ceramics. Whereas, current research in the (1-x)BZT-xBCT system is mainly focused on bulk materials, there are only few reports on thin films, associated with the challenging growth of high-quality thin films. In this work, we report on the processing and characterization of 0.5BZT-0.5BCT thin films by pulsed laser deposition (PLD) using a 248 nm line of an excimer on Pt/TiO2/SiO2/Si substrates at a temperature of 750 °C. The films were grown at 0.1 mbar oxygen pressure and different energy density in the range 4.0 - 7.8 J/cm2. The presence of the perovskite phase was confirmed by X-ray diffraction measurements. The ferroelectric nature of the films was confirmed by the butterfly features of the capacitance–voltage (C–V) characteristics and P-E hysteresis loops. The films grown at 5.5 J/cm2 exhibited superior ferroelectric properties, which are attributed to higher tetragonality (c/a ratio) and larger grain size. An electroforming free resistive switching (RS) was obtained in all films, as well as similar dependence of the RS ratio and remnant polarization on the energy density used during the deposition. The Pt/0.5BZT-0.5BCT/Au devices display, at room temperature, RS characteristics with a maximum switching ratio of ≈106, while this effect disappears at the temperature transition phas

L.L I.19
17:30
Authors : L. Borkovska, M. Osipyonok, K. Avramenko, A. Singayevsky, G. Pekar, V. Strelchuk, L. Khomenkova
Affiliations : V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Pr. Nauky 45, 03028 Kyiv, Ukraine

Resume : ZnO is widely used in solar cells, ultraviolet (UV) laser diodes, liquid crystal displays, etc. To develop the devices operating in the UV-to deep-UV spectral range, the band-gap of ZnO is increased by alloying, and MgO is usually employed as a promising material. In this work the effect of sintering temperature (TS=400-1000°C) on optical and structural properties of pure ZnO and Zn0.8Mg0.2O screen-printed films was investigated by Raman scattering and photoluminescence (PL) methods. The non-resonant Raman spectra of pure ZnO films showed that the sintering of ZnO grains begins at TS=500C, whereas for TS=900 and 1000 C an additional structural disorder in the ZnO films appears proved by both the increase of the quasi-LO peak at 585 cm-1 in the non-resonant Raman spectra and the decrease of the UV exciton-related PL emission. For the ZnMgO films the formation of the ZnMgO alloyed regions occurs already at TS=700 °C. The TS increase results in the increase of Mg content in the alloyed regions. It reaches about 20 % for TS=1000 °C, while pure ZnO phase is still observed. The coexistence of ZnO and ZnMgO phases is confirmed by the presence of both ZnO- and ZnMgO-related features in the PL and Raman spectra. The degradation of the optical properties of the films observed at higher annealing temperatures as well as much lower UV exciton-related emission from the ZnMgO regions as compared with pure ZnO are discussed in terms of Zn evaporation upon sintering procedure.

L.L I.20
17:30
Authors : Chamorro William, En Naciri Aotmane, Battie Yann,Miska Patrice, Horwat David
Affiliations : Université de Lorraine, Institut Jean Lamour, UMR7198, Nancy, F-54011, France LCP-A2MC, Institut Jean Barriol, Université de Lorraine, 1 Bd Arago, 57070 Metz, France

Resume : ZnO thin films are often used in optoelectronic devices as luminescent films or transparent electrodes due to optical properties as a large exciton energy (nearly 60 meV) a large bandgap energy (Eg) in the near UV region. However, there exists a wide dispersion of the ZnO Eg values reported in the literature. The variation could be due to the determination technique or the experimental conditions during the ZnO thin films growth. However, there is so far no clear understanding for this deviation. This work presents the synthesis of ZnO thin films by reactive magnetron sputtering and their characterization. The films have been synthesized with different O2 percentage in the Ar:O2 reactive gas mixture. From ellipsometric measurements, strong variations of Eg are observed with the synthesis conditions. Under zinc-rich conditions the presence of zinc interstitial introduces shallow donor (electrically active) defects below the conduction band modifying the absorption energy (Eg-abs) and the emission energy (Eg-em) near the band edge as probed by ellipsometry and photoluminescence, respectively. It was possible to establish an empirical relationship to relate Eg-em and Eg-abs and the Urbach energy for all experimental conditions. Thereby, it is possible to rationalize the bandgap energy dispersion in two electrostatic interaction regimes: exciton-defect or exciton-phonon interaction dominates in films with a large or low density of shallow donor defects, respectively.

L.L I.21
17:30
Authors : M. Scigaj [1], J. Gázquez [1], M. Varela [2,3], J. Fontcuberta [1], G. Herranz [1], F. Sánchez [1]
Affiliations : [1] Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain; [2] Materials Science and Technology Division, Oak Ridge National Laboratory, USA; [3] Dep. Física Aplicada III & Instituto Pluridisciplinar, Universidad Complutense de Madrid, Spain.

Resume : Interfaces between (110) and (111)SrTiO3 (STO) single crystalline substrates and amorphous oxide layers, LaAlO3 (a-LAO), Y:ZrO2 (a-YSZ), and SrTiO3 (a-STO) become conducting above a critical thickness tc. Here we show that tc for a-LAO is not depending on the substrate orientation, i.e. tc (a-LAO/(110)STO) ≈ tc(a-LAO/(111)STO) interfaces, whereas it strongly depends on the composition of the amorphous oxide: tc(a-LAO/(110)STO) < tc(a-YSZ/(110)STO) < tc(a-STO/(110)STO). It is concluded that the formation of oxygen vacancies in amorphous-type interfaces is mainly determined by the oxygen affinity of the deposited metal ions, rather than orientational-dependent enthalpy vacancy formation and diffusion. Scanning transmission microscopy characterization of amorphous and crystalline LAO/STO(110) interfaces shows much higher amount of oxygen vacancies in the former, providing experimental evidence of the distinct mechanism of conduction in these interfaces.

L.L I.22
17:30
Authors : Fatih Bayansal, Bünyamin Şahin, Mustafa Yüksel
Affiliations : Mustafa Kemal University, Mustafa Kemal University, Turgut Özal University

Resume : The effects of additives and/or dopants during the growth of thin films have been extensively studied because most of the physical properties of the films can be changed by using additives or dopants. For this reason we have deposited Zn-doped CuO composite thin films on the glass substrates by the Successive Ionic Layer Adsorption and Reaction (SILAR) method in order to investigate the effect of doping level. It was found that Zn-doping considerably influences the growth process, manipulates the band gap and modifies the particle and crystallite sizes of the films. X-Ray Diffraction (XRD) experiments evidenced that with higher doping concentrations in the growth solution the crystallite size of the films were decreased. Furthermore average particle sizes of the nanostructures are found to decrease which is consistent with the decrease in crystallite sizes calculated from the XRD results. In addition to these, transmittance, optical band gap, and activation energy values of the films are found to be increasing from the UV–Vis. and temperature dependent dc conductivity measurements with increasing Zn-doping.

L.L I.23
17:30
Authors : Dennis V. Christensen1, Felix Trier1, Yunzhong Chen1, Merlin von Soosten2, Guenevere E. D. K. Prawiroatmodjo2, Thomas S. Jespersen2, Anders Smith1 and Nini Pryds1
Affiliations : 1) Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark; 2) Niels Bohr Institute, Center for Quantum Devices and NanoScience Center, University of Copenhagen, Copenhagen, Denmark

Resume : The 2-dimensional electron gas formed at the interface between LaAlO3 and SrTiO3 has attracted a lot of interest due to its fascinating electronic structure. Compared to semiconductors, the electrons still suffer from a low carrier mobility. Substituting the deposited film with the spinel gamma-Al2O3 results in a gamma-Al2O3/SrTiO3 heterostructure exhibiting a high electron mobility thus providing a big step towards applications and mesoscopic measurements. However, it remains undemonstrated whether the plethora of fascinating properties found in the LaAlO3/SrTiO3 - such as magnetism, resistive switching and superconductivity - is observed in gamma-Al2O3/SrTiO3 as well. Here, we report a large, non-volatile resistive switching in gamma-Al2O3/SrTiO3. The resistive switching works at room temperature and is driven by a non-trivial accumulation and depletion of carriers.

L.L I.24
17:30
Authors : Felix Trier1, Guenevere E. D. K. Prawiroatmodjo2, Dennis V. Christensen1, Merlin von Soosten2, Yunzhong Chen1, Thomas S. Jespersen2 and Nini Pryds1
Affiliations : 1) Department of Energy Conversion and Storage, Technical University of Denmark, Roskilde, Denmark; 2) Niels Bohr Institute, Center for Quantum Devices and NanoScience Center, University of Copenhagen, DK-2100 Copenhagen, Denmark

Resume : We have recently realized modulation doping in disordered-LaAlO3/SrTiO3 interfaces (d-LAO/STO) with a single unit cell spacer layer of LaSrMnO3 (LSM) inserted at the interface (d-LAO/LSM/STO). This system shows metallic conductivity with electron Hall mobilities of 70,000 cm2/Vs. Here, we demonstrate patterning of the d-LAO/LSM/STO interface conductivity by use of amorphous structured LaSrMnO3 (a-LSM) thin films as a mask. This allows patterning of the interface conductivity into Hall bars with electron Hall mobilites exceeding 8000 cm2/Vs. At low temperatures, this patterned interface conduction with Hall bar geometry shows clear Shubnikov-de Haas oscillations and the clear manifestation of the quantum Hall effect.

L.L I.25
17:30
Authors : V.I. Kushnirenko (1), V.S. Khomchenko (1), T.V. Zashivailo (2)
Affiliations : (1) V. Lashkarev Institute of Semiconductor Physics, NASU, Pr. Nauky 45, Kiev 03028, Ukraine; (2) National Technical University of Ukraine “КРI”, Pr. Pobedy 37, Kiev 03056, Ukraine

Resume : ZnOS compound materials system is perspective for optoelectronic applications. Luminescent properties of the ZnOS system can be controlled by doping with Ag and Ga. In this work, we report luminescent and structural properties of ZnS–ZnO:[Ag, Ga] thin films. ZnS–ZnO:[Ag, Ga] thin films were obtained by two-stage technique as follows. At first, ZnS thin films were grown by original metal-organic chemical vapor deposition (MOCVD) under atmospheric pressure onto refractory glass substrates. Then, as-grown ZnS films were co-doped by Ag, Ga with the help of a close space sublimation method and oxidized at atmospheric pressure in air at temperature of 700°C for 1 h. Obtained ZnS–ZnO:[Ag, Ga] samples as well as reference undoped ZnS–ZnO films were studied by X-ray diffraction (XRD) technique and photoluminescence (PL) spectroscopy. PL and PL excitation (PLE) spectra were investigated at 77 and 300 K. It is found that the shape of PL spectra of the ZnS–ZnO:[Ag, Ga] films depends strongly on the preparation conditions. The PL spectra of the films are consist of bands with the peak maxima at 450 and 500 nm. A detailed analysis of the PL and PLE spectra at various excitation intensities allows us to obtain the data, from which an origin of emission centers is elucidated. The possible origin of radiative transitions is discussed.

L.L I.26
17:30
Authors : B.A. Orlowski, A. Pieniazek,
Affiliations : Institute of Physics PAS: Al. Lotnikow 32/48: 02-668, Warsaw: Poland

Resume : The typical heterojunctions of p - n type semiconductors with the band gap in the range of energy (1 to 2eV, solar spectrum, Si, GaAs, CdTe) creating the cell with the wide band gap transparent n-type semiconductors like eg. GaN, ZnO, SiC, ZnTe, will be considered. The correlations of the change of Quasi Fermi Level position, minority carriers concentration and corresponding to it value of photovoltage will be presented and discussed. Under cell illumination the same densities n = p of carriers are generated, but it is causing bigger change of Quasi Fermi Level energy of minority than of majority carriers. The difference of these levels energies corresponding to the cells of electrons and holes contribute to value of generated photovoltage. It allows to estimate corresponding to it change of the minority carriers concentration, as well as to scan the part of the band gap energy region by the Quasi Fermi Level of minority carriers and obtain e.g. pinning of the Fermi level. For general theoretical description the main set of equations [3] can be used. [1]. A. Przezdziecka, at al., Sensors and Actuators A195 ( 2013) 27 ? 31. [2]. R. Pietruszka, at al., Mat.Sci.Semic. Proc.,25 (2014) 190-196. [3]. L. Sosnowski, B. Orlowski, phys.stat.sol. (a) 3, 117 (1970) Supported by PNCRD (NCBiR) Project DZP/PBSII/1699/2013.

L.L I.27
Start atSubject View AllNum.
 
Integration of functional oxides with silicon : Wilfrid Prellier
09:00
Authors : Matjaž Spreitzer1, Dejan Klement1, Zoran Jovanović1,2, Danilo Suvorov1
Affiliations : 1 Advanced Materials Department, Jožef Stefan Institute, Slovenia 2 Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, Belgrade, Serbia

Resume : Control at silicon-oxide interfaces is of great importance since it enables high-quality integration of oxide materials with Si platform and thus provides versatile additional functionalities to semiconductor industry. However, the ability to control such interfaces is hindered by the intense reaction of constituents. Therefore Si has to be passivized, which is normally performed by the formation of an appropriate buffer layer that is chemically stable in the oxygen rich environment, as well as structurally compatible with silicon and the oxide. In our study pulsed laser deposition (PLD) was used to prepare Sr- and SrO-based buffer layers, which have been so far prepared successfully only using molecular beam epitaxy method. By optimization of deposition conditions we were able to monitor Si surface reconstructions during PLD of Sr and SrO using the reflection high-energy electron diffraction (RHEED) technique. In case of Sr we observed characteristic two-domain (2×3)+(3×2) pattern at 1/6 ML Sr coverage and (1×2)+(2×1) pattern at ½ ML Sr coverage. This enabled us to control the surface coverage at the atomic level, which is needed for proper Si passivization. Subsequently, epitaxial layer of SrTiO3 with STO(001)║Si(001) and STO[110]║Si[100] was grown on as-prepared buffer layers and analyzed using different analytical techniques. Results of our study revealed new PLD-based path towards epitaxial integration of SrTiO3 and other functional oxides with Si.

L.6.1
09:30
Authors : R. Moalla1, B. Vilquin1, G. Saint-Girons1, G. Sebald2, N. Baboux3, R. Bachelet1
Affiliations : 1 INL-CNRS, Ecole Centrale de Lyon, Ecully, France 2 LGEF, INSA de Lyon, Villeurbanne, France 3 INL-CNRS, INSA de Lyon, Villeurbanne, France

Resume : Pyroelectric materials, in which a change in polarization occurs in response to a change in temperature, can provide thermal energy harvesting for electrical generation in compact systems with temporal temperature variation and can be used for cooling applications via the electrocaloric effect [1]. According to the structural dependence of electric properties and to recent reports, single-crystalline pyroelectric films should provide an enhanced conversion energy efficiency with respect to bulk or polycrystalline materials [2]. In this communication, we will show the impact of the domain-orientation on the ferroelectric and pyroelectric properties of epitaxial PbZr0.52Ti0.48O3 films tuned by the thermal expansion mismatch with the substrate. SrTiO3(001) and Si(001) substrates are used to generate different orientations of the ferroelectric domains. The intrinsic pyroelectric coefficient is revealed to be much larger along the polarization axis and it can reach -450 µC/m2K in c-oriented films, compared to -320 µC/m2K in a-oriented films [3]. The corresponding harvested pyroelectric energy can be beyond 10 mJ/cm3 per cycle for temperature variations of 10°C, and temperature changes of more than 10°C can be reached close to room temperature under high electric field, that could provide cooling solutions for electronic components. [1] S.B. Lang, Phys. Today 58, 31 (2005) [2] G. Sebald et al., Smart Mater. Struct. 18, 125006 (2009) [3] R. Moalla et al., submitted

L.6.2
09:45
Authors : R.Groenen, R. Hoekstra, E. Rodijk, C.A.J. Damen, K.Orsel, H.M.J. Bastiaens, K.J. Boller, G. Koster, G. Rijnders
Affiliations : Twente Solid State Technology, MESA+ Institute for Nanotechnology, University of Twente, The Netherlands P.O. Box 256, 7500 AG Enschede, The Netherlands E-mail: groenen@tsst.nl Phone: +31(0)53 2030 244

Resume : Pulsed Laser Deposition (PLD) has been established in recent years as a versatile thin film deposition technique for the near stoichiometric synthesis of materials including complex transition metal oxide thin films. These oxides offer a variety of exploitable properties and, when combined, new functionalities due to electronic reconstruction at interfaces. Despite this rich potential for use in electronics, actual applications are relatively few as they rely on full control of thin film growth on atomic scale with substrate materials at sizes suitable for industrial applications. We present the latest results on optimized growth and characterisation of ferromagnetic LSMO on YsZ/(CeO2)/(SRO) on 4” silicon wafers utilizing a TSST developed large-area PLD system. X-ray diffraction measurements show a high degree of (buffer layer dependent) epitaxy and crystallinity over the full wafer comparable to small scale PLD grown films. Furthermore, it is shown that growth parameters do not trivially scale from small area deposition settings. For LSMO, at typical ‘small-area’ temperature settings of up to 700°C, no epitaxy is observed, where at elevated temperature, a high degree of epitaxy is obtained. This is understood by recent improved understanding on the composition of the plasma, in which the oxidation of species in the plasma is suggested to be a crucial mechanism in the stoichiometric reconstruction of the synthesized oxide thin films1. 1. R. Groenen et al. Subm. APL mat.

L.6.3
10:00
Authors : A. Carretero-Genevrier1, Judith Oró-Solé 2, Jaume Gázquez 2, Teresa Puig 2, Xavier Obradors2, Clément Sanchez3, Etienne Ferain4, Juan Rodríguez-Carvajal5, Narcís Mestres2*
Affiliations : 1 Institut des Nanotechnologies de Lyon (INL) CNRS, 36 avenue Guy de Collongue, 69134 Ecully, France; 2 Institut de Ciència de Materials de Barcelona ICMAB-CSIC, Campus UAB 08193 Bellaterra, Spain; 3 Laboratoire Chimie de la Matière Condensée, UMR UPMC-Collège de France-CNRS 7574. Collège de France, 11 place Marcelin Berthelot, 75231 Paris, France; 4 it4ip sa, 1 avenue Jean-Etienne Lenoir, 1348 Louvain-la-Neuve, Belgium; 5 Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France

Resume : Monolithic direct integration of functional oxide nanowires with vertically oriented crystals on a semiconductor platform is challenging due to difficulties on preserving epitaxy, crystalline phase, and composition. Here, we developed a new strategy to produce vertical epitaxial single crystalline manganese oxide based nanowires thin films with tunable composition and enhanced ferromagnetic properties on Si substrates by using a chemical solution deposition approach [1]. The nanowire growth mechanism involves the use of track-etched nanoporous polymer templates combined with the controlled growth of quartz thin films at the Si surface, which allowed the epitaxial stabilization and crystallization of the oxide nanowires. α-quartz layers were obtained by thermally activated devitrification of the native amorphous silica surface layer assisted by a heterogeneous catalysis driven by alkaline earth cations (Sr2+, Ba2+ or Ca2+) present in the precursor solution [2]. Therefore, the combination of soft-chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional complex oxides nanomaterials on Si substrates [3]. References [1] A. Carretero-Genevrier et al. Chem.Soc.Rev. 43, 2042 (2014) [2] A. Carretero-Genevrier et al. Science 340, 827 (2013) [3] A. Carretero-Genevrier et al. Chem. Mater. 26, 1019 (2014)

L.6.4
10:15
Authors : L. M?chin1, B. Guillet1, S. Liu1, A. Aryan1, V. Marquez do Nascimento1,2, M.E.B.G.N Silva1,3, C. Adamo4, D.G. Schlom4,5
Affiliations : 1GREYC (UMR 6072) CNRS ENSICAEN Universit? de Caen Basse-Normandie, 14050 Caen cedex, France 2Federal University of Campina Grande, Campina Grande 58429-900, Brazil 3CCS ? UNICAMP ? Rua Jo?o Pandia Cal?geras 90, POB 6101, 13083-870 ? Campinas/SP, Brazil. 4Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853-1501, USA 5Kavli Institute at Cornell for Nanoscale Science, Ithaca, New York 14853, USA

Resume : A bolometer is a thermal detector, which means that the incoming radiation is measured by the temperature elevation caused by its absorption. La0.7Sr0.3MnO3 (LSMO) is a promising material for the realization of uncooled bolometers because it shows a large resistance variation with temperature at room temperature. The Temperature Coefficient of the Resistance (TCR defined as 1/R?dR/dT) is around 0.02 K-1 at 300 K. LSMO also exhibits very low noise level compare to other resistive materials [1]. Square geometries of areas ranging from 50 ?m ? 50 ?m to 200 ?m ? 200 ?m were studied in both suspended and non suspended configurations and on various substrates, such as buffered Si (001), SrTiO3 (001) and MgO (001) [2, 3, 4]. This paper will present a summary of electro-thermal characterization as well as low frequency noise, optical and infrared characterization of the fabricated bolometers. For both cases, a simple thermal model is presented, and compared to experiments, which allow to give conclusions about optimized geometries depending on the targeted detector size [5]. References : [1] L. M?chin, et al., J. Phys. D: Appl. Phys. - Fast Track Communication 46 202001 (2013). [2] L. M?chin, et al., Physica Status Solidi A Vol. 209 (6) 1090-1095 (2012). [3] C. Adamo, et al., APL Materials 3 062504 (2015). [4] S. Liu, et al., Microelectronic Engineering Vol. 111, 101-104 (2013). [5] A. Aryan, et al., Appl. Surf. Science 326 204 (2015).

L.6.5
10:30 Coffee break    
11:00 IFOX talks (Participants to symposium L are invited to attend this session)    
12:30 Lunch break    
 
Oxide thin film growth I : Yunzhong Chen
14:00
Authors : W. Prellier
Affiliations : Laboratoire CRISMAT, CNRS UMR 6508, ENSICAEN, 6 Bd Mal Juin, 14050 Caen Cedex, France

Resume : Interest in thin film transition metal oxides is driven in part by the potential technological application of devices exploiting intriguing phenomena, i.e. oxide electronics, and in part by the novel structures and properties observed in epitaxial oxide films, using phase, strain, and interfacial engineering. However, in spite of the large number of observations and promise of epitaxial oxide thin films, most of the investigations have been focused on films on low-index commercially-available single-crystal substrates, which have limited the scope of the study. Here, we present a novel high-throughput synthesis process (called combinatorial substrate epitaxy) where an oxide film is grown epitaxially on a polycrystalline substrate, and applied it to the growth of Ca2MnO4 or BiFeO3 materials. Using EBSD, we determine the preferred epitaxial orientation relationships, and also show how functional properties could be investigated across the entirety of epitaxial orientation space, and provide a library of physical property observations, that can finally be applied to a wide range of complex functional oxides. Support from ANR, MEDILIGHT and MEET are acknowledged.

L.7.1
14:30
Authors : Dashan Shang,1,2 Peining Li,2 Tao Wang,2 Egidio Carria,2 Jirong Sun,1 Baogen Shen,1 Thomas Taubner,2 Ilia Valov,3 Rainer Waser,3 and Matthias Wuttig2
Affiliations : 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2I. Physikalisches Institut (IA), RWTH Aachen University, 52074 Aachen, Germany 3Institute für Werkstoffe der Elektrotechnik II, RWTH Aachen University, 52074 Aachen, Germany & Peter Grünberg Institute (PGI-7), Forschungszentrum Juelich, Juelich, Germany

Resume : An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in solid electrolyte with low ion mobility and are expect to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.

L.7.2
14:45
Authors : Timo Schumann, Santosh Raghavan, Susanne Stemmer
Affiliations : Materials Department, University of California, Santa Barbara, California 93106-5050, USA

Resume : Bulk crystals of perovskite rare-earth stannates have been shown to possess high charge carrier mobilities of 300 cm^2/Vs at room temperature [1], while possessing large band gaps (3.1 eV and 4.7 for BaSnO3 and SrSnO3). In this contribution we present epitaxial growth of thin BaSnO3 films via molecular beam epitaxy (MBE). Solid-source high temperature Knudsen cells are used to provide Ba and Sn, while oxygen is provided by an rf-plasma source. La is used as electrical dopant. We investigate the impact of the different growth parameters (i.e. substrate temperature, fluxes, and choice of substrate) on the synthesis of the stannate films. Structure and morphology are characterized by X-ray diffraction (XRD) measurements and atomic force microscopy, while the electrical properties are determined by van-der-Pauw magnetotransport measurements. In-situ reflective high energy electron diffraction measurements show streaky patterns, indicating the growth of smooth and planar films. XRD measurements confirm the synthesis of single phase BaSnO3 under optimized growth conditions. The results are discussed in context of employing MBE for the growth of high quality stannate films and heterostructures for high mobility oxide devices. [1] Kim, H. J. et al. Appl. Phys. Express 5, 061102 (2012).

L.7.3
15:00
Authors : Mitsuaki Yano1, Kazuto Koike1, Masayuki Matsuo1, Takayuki Murayama1, Yoshiyuki Harada1, and Katsuhiko Inaba2
Affiliations : 1: Nanomaterials Microdevices Research Center, Osaka Institute of Technology Asahi-ku Ohmiya, Osaka 535-8585, Japan 2: X-ray Research Laboratory, Rigaku Corporation Mtsubaracho. Akishima 196-8666, Japan

Resume : MoO3 and WO3 have been widely studied for the applications to catalysts, gas sensors, smart windows, photovoltaic cells, electrodes for OEL, and solid electrolyte batteries. These two materials are also promising for semiconductor devices due to their wide bandgap energies, high stability in air, and capability of intercalatable layered structures although limited works have been reported for the epitaxial thin film growth. Previously, we reported the growth of MoO3 films on sapphire substrates by molecular beam epitaxy [1,2]. In this presentation, we extend the growth technique to WO3 and MoO3/WO3 films. We grew these films on r-plane sapphire substrates from compound sources of MoO3 and WO3, and O* radicals. The WO3 films were amorphous when the growth temperature TG was kept below 300°C. At 400°C ≤ TG ≤ 600°C, the films became monoclinic polycrystal with mixed orientations of a-, b-, and c-axes. At TG = 700°C, they turned to be c-axis oriented films although the FWHM of XRD rocking curves (XRC-FWHM) for 200-nm-thick films was as broad as several thousands of arcsec with a ~5 nm RMS roughness due to development of dense thermal etchpits. Since the XRC-FWHM was found to increase with film thickness, we grew the WO3 films using a two-step growth method; the initial 15 nm was grown at TG = 700°C, and the rest 185 nm was at TG = 500°C. By using the two-step growth, c-axis oriented WO3 films with a narrow XRC-FWHM of less than 100 arcsec with a smooth surface of ~1 nm RMS roughness were obtained. At the symposium session, we will also report the MoO3 heteroepitaxial growth on top of the smooth c-axis oriented WO3 surface. [1] K. Koike et al., Jpn. J. Appl. Phys. 53, 2014, 05FJ02. [2] K. Inaba et al,, 8th Intern. Workshop on ZnO and Related Materials, Ontario, 2014, Sep. 7-11.

L.7.4
15:15
Authors : Tsukasa Katayama, Akira Chikamatsu, H. Kamisaka, Tomoteru Fukumura, and Tetsuya Hasegawa
Affiliations : The University of Tokyo; The University of Tokyo, JST-CREST; Tohoku University, JST-CREST; The University of Tokyo, JST-CREST, KAST

Resume : Transition metal oxyhydrides have recently been synthesized through low-temperature topotactic reactions. For example, LaSrCoO4 can be transformed to LaSrCoO3H0.7 by annealing with CaH2 [1]. In this study, we successfully synthesized new perovskite SrCoOxHy thin films via topotactic hydrization of brownmillerite SrCoO2.5 epitaxial thin films on SrTiO3 (001) substrates with CaH2. The perovskite-type cation coordination was maintained during the topotactic treatment due to epitaxial stabilization on the substrate. Structural and chemical analyses suggested that the doped hydride ions form two-dimensional network of Co-H−-Co bonds. The SrCoOxHy thin film exhibited much higher resistivity (> 104 Ωcm at 300 K) and larger bandgap (~2.1 eV) than those of the SrCoO2.5 precursor. [1] Science 2002, 295, 1882.

L.7.5
15:30 Coffee break    
 
Ferroelectric thin films II : Jacobo Santamaria
16:00
Authors : Jean Fompeyrine
Affiliations : IBM Research GmbH

Resume : During the last 10 years, the quest for a replacement gate dielectric in field effect transistors has been a powerful driver to investigate the deposition of ultra thin oxide thin films. Replacing SiO2?with HfO2?in transistors was a major breakthrough for the microelectronic industry and generated a lot of know-how. This knowledge is today cross-fertilizing research areas beyond traditional CMOS microelectronics. Controlling the interface between the oxide and silicon has for example always been a key issue. This specific research triggered the development of new deposition processes, enabling researchers to grow high quality, crystalline, complex oxide films onto silicon. Such ?functional? oxides have physical properties that make them very attractive to perform functions that will be required in future Information and Communication Systems. In particular, technologies must be developed that enable a performance scale-up of the full system, while having stagnating data processing capabilities at the chip level. Silicon photonics is emerging as one of the technology of choice for this purpose. Electro-optical oxides are therefore an extremely important area of research to enable the integration of new functionalities in advanced silicon photonics. This presentation will deal with the opportunities and challenges to combine silicon microfabrication techniques with the capability to grow crystalline directly on silicon. It will in particular focus on the use of ferroelectric perovskites for photonic circuits in future systems, and how defect chemistries might play a crucial role.?

L.8.1
16:30
Authors : Philipp Komissinskiy, Aldin Radetinac, Arzhang Mani, Mohammad Nikfalazar, Yuliang Zheng, Alex Wiens, Rolf Jakoby, Lambert Alff
Affiliations : Institute for Materials Science, TU Darmstadt, Germany; Institute for Microwave Engineering and Photonics, TU Darmstadt, Germany

Resume : Thin-film ferroelectric varactors are considered for applications in tunable electric devices at gigahertz frequencies due to highly tunable capacitance, fast tuning speed, and low power consumption. We present our studies of metal-insulator-metal (MIM) Au/Pt/Ba_xSr1-xTiO3/SrMoO3 varactors, where epitaxial tunable dielectric BaxSr1-xTiO3 (BST) is grown on a single-crystalline SrMoO3 (SMO) conducting electrode. SMO single crystals exhibit the lowest resistivity of 5.1 µΩ∙cm among all known perovskite oxides. Using pulsed laser deposition, we grow single-crystalline SMO films with thicknesses up to 500 nm and room-temperature resistivity below 30 µΩ∙cm at frequencies up to 20 GHz [1]. The fabricated circular MIM varactors of 10-20 µm in diameter show relative capacitance tunability above 30 % at low voltages of 5 V at room temperature. The varactor quality factor up to 50 is observed at 1 GHz. Thus, the resulting figure of merit (FOM) of the varactors with SMO electrodes is above 1000 at 1 GHz, which is more than 2 orders of magnitude higher than FOM reported so far for any other MIM varactor with oxide electrodes. [1] A. Radetinac et al., Appl. Phys. Lett. 105, 114108 (2014).

L.8.2
16:45
Authors : Alichandra Castro,1 Brian J. Rodriguez,2 Paula M. Vilarinho,1 Paula Ferreira1
Affiliations : 1 Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal 2 Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland

Resume : Semiconductor industry has been characterized for more than five decades by a fast rate of development in its products and a continuous trend of scaling down the devices. However since 2007 a new concept, ?More than Moore? that addresses functional diversification, has emerged. Besides the small size, devices should incorporate functionalities that provide additional value to the end customer. A great degree of creativity on the design of the materials is required. Based on this, we have been developing a pioneer work of preparing and characterizing ferroelectric porous thin film matrices to understand the effect of the nanostructure on the final properties of the materials and if the porosity can be a good way to achieve multifunctional materials.[1,2] Here, we prepare thin films of lead titanate films by dip-coating deposition of a sol-gel solution containing an amphiphilic block co-polymer, followed by evaporation-induced self-assembly (EISA).[2] Dense films and porous films with thickness ranging from 100 nm to 22 nm were prepared and structural and morphological characterized. The porous films exhibit always enhanced piezoelectric coefficients, switchable polarization, low local coercivity and critical voltage for the same thermal conditions. The thinnest film present reduced vertical imprint in the hysteresis loop measured by Piezo Force Microscopy, indicating that that films due to the high level of porosity have reduced strain effects from the substrate. Acknowledgement Project CICECO - Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013), financed by Portuguese funds through the FCT/MEC and when applicable co-financed by FEDER under the PT2020 Partnership Agreement. Authors are grateful to FCT and POPH/FSE, for doctoral fellowship SFRH/BD/67121/2009 and investigator fellowship IF/00327/2013. Some of the measurements were performed on equipment funded by Science Foundation Ireland (SFI07/IN1/B931). 1. P. Ferreira, R. Z. Hou, A. Wu, M.-G. Willinger, P. M. Vilarinho, J. Mosa, C. Laberty-Robert, C. Boissi?re, D. Grosso, C. Sanchez, Langmuir 2012, 28, 2944. 2. A. Castro, P. Ferreira, B. Rodriguez, and P. M. Vilarinho, J. Mater. Chem. C 2014, 3, 1035.

L.8.3
17:00
Authors : E Buixaderas, C Kadlec, D Nuzhnyy, I Rychetsky, J Petzelt H Ursic, B Malic,
Affiliations : Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8, Czech Republic Department of Electronic Ceramics, Jožef Stefan Institute, Ljubljana, Slovenia

Resume : The evaluation of the dielectric response in thick films of dielectric materials and in mixtures of dielectric and metals is not as straightforward as in bulk materials, due to the presence of porosity. To simulate the effective dielectric function of these films, porosity and percolation effects should be taken into account in the theoretical models. The case of the mixture of a ferroelectric with a metal, is specially interesting because the dielectric response can be greatly enhanced, and near the percolation threshold the permittivity diverges. This effect is discussed for a set of thick Pb(Zr,Ti)O3 films and composite films Pb(Zr,Ti)O3 −xPb2Ru2O6.5 prepared by screen printing on sapphire substrates. Their homogeneity and phonon response were studied by Raman spectroscopy and Fourier-transform infrared (FTIR) reflectivity. The dielectric response below phonons was measured using time-domain terahertz transmission spectroscopy. The compositions, up to 25 vol% Pb2Ru2O6.5, are below and above the electrical percolation threshold, known to be about 17% in the bulk composites. Using the dielectric functions of bulk PZT ceramics and Pb2Ru2O6.5 single crystals, the effective dielectric functions can be compared with those obtained using the theoretical models. D Nuzhnyy, E Buixaderas J. Petzelt et al, J. Physics D: Appl. Phys 47 (2014) 495301 (2014).

L.8.4
 
Poster session II : F. Sanchez, G. Koster, Y. Chen, V. Craciun
17:30
Authors : Sven Dirkmann, Jan Trieschmann, Tobias Gergs, Mirko Hansen, Martin Ziegler, Hermann Kohlstedt, Thomas Mussenbrock
Affiliations : Ruhr-Universität Bochum, Lehrstuhl für Theoretische Elektrotechnik, 44780 Bochum, Germany; Christian-Albrechts-Universität zu Kiel, Technische Fakultät, Nanoelektronik, 24143 Kiel, Germany;

Resume : Memristive devices are promising candidates for neural network applications. Many of these devices rely on nano-ionic mechanisms, one of which is electrochemical metalization. Here, the resistive switching, i.e., the drastic change of the ohmic resistance is due to the formation and re-formation of conductive metal filaments. Particularly the switching, which is inherently a 3D phenomenon, on the experimental seconds time-scale is not understood yet. In this contribution we report on a new 3D simulations model for filamentary resistive switching. In order to allow for describing the interplay between ionic and electronic transport, the 3D kinetic Monte-Carlo model for the ion transport is equipped with a simplified current transport model. First simulation results on the switching dynamics discussed in this contribution show very good agreement with experimentally obtained data. This work is part of the Research Group FOR2093 entitled “Memristive Devices for Neural Systems” and funded by the German Research Society (DFG)

L.L II.1
17:30
Authors : Hana Ursic1,2, Andreja Bencan1,2, Barbara Malic1,2, Evgeniya Khomyakova1,2, Julian Walker1, Maja Makarovic1,2, Dragan Damjanovic3, Tadej Rojac1,2
Affiliations : 1Electronic Ceramics Department, Jozef Stefan Institute, 1000 Ljubljana, Slovenia; 2Jožef Stefan International Postgraduate School, Jamova cesta 39, 1000 Ljubljana, Slovenia; 3Ceramics Laboratory, Swiss Federal Institute of Technology – EPFL, 1015 Lausanne, Switzerland

Resume : BiFeO3 (BFO) has been subject of unprecedented interest with thousands of published papers. In contrast to the considerable advancement achieved in BFO thin films, the properties of polycrystalline ceramics and thick films are still insufficiently understood. In this contribution we will compare and discuss electrical and electro-mechanical properties of BFO ceramics and thick films probed at a local level using conductive atomic-force (C-AFM) and piezo-force (PFM) microscopy. The piezoelectric response of BFO is characterized by nonlinearity and hysteresis, which can be attributed to the irreversible motion of non-180° domain walls. What distinguishes BFO from other ferroelectrics is the low-frequency nature of the nonlinearity, i.e., a strong nonlinear response was observed only at low driving field frequencies (mHz-to-Hz range), suggesting coupling of electric conductivity and piezoelectric nonlinearity. Detailed analysis of the domain structure with PFM and local electric properties of domain walls with C-AFM, revealed the origin of the particular macroscopic piezoelectric behaviour of BFO [1]. Attention will be given also to the domain structure and local conductivity of samarium, gadolinium and dysprosium modified BFO ceramics. [1] T. Rojac, H. Ursic, A. Bencan, B. Malic, D. Damjanovic, Adv. Funct. Mater., 25, 2015. The work was supported by the SRA (P2-0105, J2-5483), CO-NAMASTE and Swiss National Science Foundation (PNR62, 406240-126091).

L.L II.2
17:30
Authors : C. Ferrater1, J. Garcia-Valenzuela1, L. Rodriguez2, M.C. Polo1, J. Bertomeu1, J.M. Asensi1, J. Andreu1, M. Varela1
Affiliations : 1 Departament de Fisica Aplicada i Optica, Universitat de Barcelona, Spain; 2 ICN2-Institut Catala de Nanociencia i Nanotecnologia, CSIC Campus de la UAB, Bellaterra, Spain.

Resume : Thin film layers of Al2O3 present a clear technological interest in a variety of applications: as surface passivation on top of silicon wafers in photovoltaic technology [1], as a dielectric covering layer for carbon nanotubes or graphene layers [2], as a blocking electrode in organic photovoltaic devices using a conformal deposition of Al2O3 on TiO2 or columnar ZnO [3,4], and, doped with Er, as optical amplifiers or lasers in planar optoelectronic applications [5]. The most common techniques used to grow Al2O3 layers are chemical vapour deposition (CVD) and atomic layer deposition (ALD). The purpose of this work is to study the structural and bonding properties of Al2O3 films obtained with r.f. magnetron sputtering and pulsed laser deposition (PLD). The influence of the different deposition parameters, like substrate temperature or oxygen partial pressure and film thickness, on the properties of the deposited layers will be considered. The samples have been analysed by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results will be discussed to evaluate the suitability of each technique for the different potential applications. [1] B. Hoex et al, Applied Physics Letters 91, 112107 (2007) [2] Steven M. George, Chem. Rev. 2010 (110) 111 [3] E. Palomares et al. J. Am. Chem. Soc. 2003 (125) 475 [4] M. Law et al J. Phys. Chem. B 2006 (110) 22652 [5] Polman A., J. Appl. Phys. 82 (1) 1

L.L II.3
17:30
Authors : Joon-Shik Park, Kwang-Bum Park, Seong-Dong Kim
Affiliations : Korea Electronics Technology Institute (KETI)

Resume : Recently, the researches regarding the detection and analysis of exhaled breath gases from human body have been actively done [1,2] because some target gases can be used for bio-markers of diseases. In order to detect exhaled gases, the micro gas sensor array technology is one of key technologies due to cost-effectiveness and miniaturization. A micro gas sensor array including a Si based single chip micro-platform and two kinds of sensing nanomaterials were designed and fabricated. A single chip micro-platform was fabricated using thin film processes and MEMS techniques as presented by authors [3]. In this work, two kinds of sensing nanomaterials included SnO2 nanoparticles and WO3 nanoparticles based composite materials, respectively. Each sensing nanomaterial was applied to 8 elements. The 8 elements in a micro gas sensor array had same sensing material. So, two kinds of sensing materials were applied to total 16 elements on a single chip micro-platform. Through our preliminary work, the fabricated micro gas sensor array was characterized to 147 ppm NH3, 2.3 ppm NOx, and 147 ppm CO gases. We are going to present the measured sensitivity data to figure out the gas sensing behavior related with two kinds of sensing nanomaterials. [1] G. Peng et al, Nature Nanotechnology, 4 (2009) 669~673. [2] C. Lourenço et al, Metabolites, 4 (2014) 465-498. [3] J-.S. Park et al, MNE 2014, Lausanne, Sept. 22~26, 2014, 92.

L.L II.4
17:30
Authors : J. Gan1*, Y. Ievskaya2, R.L.Z. Hoye2, B. G. Svensson1, E. V. Monakhov1 and J.L. MacManus- Driscoll2
Affiliations : 1University of Oslo, Department of Physics /Center for Materials Science and Nanotechnology, P.O. Box 1048 Blindern, N-0316 Oslo, Norway 2Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, CB3 0FS, Cambridge, UK

Resume : Oxide based heterojunction (HJ) thin film solar cells, specifically with intrinsic p-type Cu2O (band gap Eg=~2.1 eV) as the absorber layer, have a theoretical efficiency up to 18% [1], while currently reported experimental values remain between 2~6% [2][3]. Defects, particularly the interface defects, are considered as recombination centres for photon-generated carriers and therefore are mainly responsible for limiting the efficiency in such HJ solar cells. For further understanding and improvements in efficiency, it is necessary to investigate the interface of the Cu2O based heterojunction. In this work, an equivalent lumped circuit model was established to simulate the dielectric properties of the HJ interface, where a pair of parallel connected capacitance/conductance elements was used to describe the electrical activities of capture and emission in a defect state at different measurement frequencies. The response of carriers captured by interface defects is reduced with an increasing measurement frequency, thus capacitance is reduced accordingly. In the model, the capacitance differential ω·dC/dω was used to determine the interface trap density by sweeping the frequency. The relation between the capacitance differential ω·dC/dω and defect density was developed based on a lumped circuit model. Furthermore, interfacial trap density was assessed in ZnO/Cu2O solar cells that have been fabricated with thermally oxidized Cu2O and electrochemically deposited Cu2O, which was found to correlate with the solar cell performance. Reference [1] J. J. Loferski, J. Appl. Phys. 27, 777 (1956). [2] A. Mittiga, E. Salza, F. Sarto, M, Tucci, R. Vasanthi, Appl. Phys. Lett. 88, 163502 (2006). [3] T. Minami, Y. Nishi, T. Miyata, Thin Solid Films 549, 65 (2013).

L.L II.5
17:30
Authors : Saikumar Inguva, Ciarán Gray, Enda McGlynn, Jean-Paul Mosnier
Affiliations : School of Physical Sciences and National Centre for Plasma Science and Technology, Dublin City University, Dublin 9, Ireland.

Resume : In this work, we report the growth of vertically aligned ZnO nanorods with excellent optical quality. These were grown by catalyst free vapor phase transport (VPT) on ZnO seed layers. The latter were prepared on Si (100) substrates by pulsed laser deposition (PLD) at a temperature of 450 °C and in an O2 ambient pressure of 100 mT. The ZnO nanorods were then grown by VPT on these ZnO-seeded Si substrates at 900 °C using an Ar gas flow rate of 90 sccm. XRD, SEM, EDX and low-temperature (10 K) PL were used to characterize the as-grown ZnO nanorods. XRD evidenced highly textured ZnO nanorods with uniform c-axis orientation normal to the substrate surface. The c-axis lattice spacing and average crystallite size of the ZnO material were 0.259 nm and 38 nm, respectively. SEM images showed vertically well-aligned nanorods with average individual height and width of ~ 800 nm and ~ 100 nm, respectively and a surface coverage density of ~ 4 per m2. EDX showed the stoichiometry of the deposit was ZnO0.9. Low-temperature PL spectra were dominated by a strong I6 (3.36 eV), and also showed emission from the surface exciton (3.3728 eV) and the free exciton (3.3783 eV). Additional features included a two electron satellite (TES ~ 3.320 eV) and longitudinal optical replicas (1LO ~ 3.290 eV, 2LO ~ 3.217 eV and 3LO ~ 3.145 eV) of the bound exciton (BX), as well as the LO replicas of the TES (TES 1LO ~ 3.251 eV and TES 2LO ~ 3.182 eV). A comparatively weak green band was also observed. These data reflect the excellent optical quality of these ZnO nanorods. Overall, the work shows that high quality ZnO nanorods can be prepared by VPT directly on PLD grown ZnO seed layers.

L.L I.6
17:30
Authors : A.V. Shylo1, O.S. Doroshkevych1, 2, T.Yu. Zelenyak1, T.E. Konstantinova1
Affiliations : 1Donetsk Institute for Physics and engineering named after O.O.Galkin of the National Academy of Sciences of Ukraine, Nauki ave, 46, Kyiv, Ukraine 2Joint Institute for Nuclear Research, Joliot-Curie Str., 6, 141980, Dubna, Russia

Resume : High value of phase boundaries in dispersed systems based on nanopowders is one of advantages compared with coarse-grained analogues. At presence on outer side of border of adsorption ionic atmospheres with work function, different from electron work function of nanoparticles material, nanoparticle has heterojunction properties. Changes of external conditions will change electrical properties of heterojunction. This property can be used as a sensor. The aim was to study electrical properties of porous dispersed system based on ZrO2 nanoparticles by method of impedance spectroscopy in depending from ambient humidity. As the object of investigation compacts from ZrO2+3molY2O3 (700°C) nanopowder were used. Impedance was measured by the Measurer-analyzer of impedance parameters type 2V-1 in the climatic chamber with adjustable humidity over a wide range (40-90%RH). The frequency dependence of imaginary and real components of the complex impedance was recorded. With the use of author's method, contribution of surface and volume components to overall conductivity was estimated. Relationship between air humidity and electrical resistance of samples was established. Increase of humidity from 39 to 94% leads to decrease of total sample resistance by 25 times (from 0.46kOhm to 11.51MOhm). The determining role of the adsorption layer (surface component of impedance) in conductivity was found. These studies provide a base for development of nano-ionic humidity sensor of high sensitivity.

L.L II.6
17:30
Authors : Ibtissam Dani, Najim Tahiri, Hamid Ez-Zahraouy* and Abdelilah Benyoussef
Affiliations : Physique Informatique

Resume : The effect of the bi-quadratic exchange coupling anisotropy on the phase diagram of the spin-1 Blume-Emery-Griffiths model on simple-cubic lattice is investigated using mean field theory (MFT) and Monte Carlo simulation (MC). It is found that the anisotropy of the biquadratic coupling favors the stability of the ferromagnetic phase. By decreasing the parallel and/or perpendicular bi-quadratic coupling, the ferrimagnetic and the antiquadrupolar phases broaden in contrast, the ferromagnetic and the disordered phases become narrow. The behavior of magnetization and quadrupolar moment as a function of temperature is also computed, especially in the ferrimagnetic phase.

L.L II.7
17:30
Authors : Małgorzata Sowińska1*, Karsten Henkel1, Chittaranjan Das1, Irina Kärkkänen2, Jessica Schneidewind2, Bernd Gruska2, Cay Pinnow2, Hassan Gargouri2, and Dieter Schmeißer1
Affiliations : 1Brandenburgische Technische Universität Cottbus-Senftenberg, Konrad-Wachsmann Allee 1, 03046 Cottbus, Germany; 2SENTECH Instruments GmbH, Schwarzschildstraße 2, 12489 Berlin, Germany; *sowinska@tu-cottbus.de

Resume : Titanium oxynitride (TiOxNy) films are interesting materials due to their remarkable optical and electronic properties. Depending on the O/N ratio they combine properties of oxides (optical) and nitrides (hardness, wear resistance). N-rich TiOxNy films are applied as anti-reflective coatings [1] and biomaterials [2], while O-rich films are used as thin film resistors [3] and solar selective collectors [4]. In the past, the TiOxNy layers have been mainly deposited by reactive magnetron sputtering. However, sputtering has some inherent disadvantages, such as high stress appearance and defect formation within the films [5]. The plasma enhanced atomic layer deposition (PEALD) method [6] circumvents these drawbacks and enables the growth of high-quality thin films. We report on TiOxNy films prepared by PEALD employing two precursor types. We used titanium(IV)isopropoxide (TTIP) and tetrakis(dimethylamino)titanium (TDMAT) as Ti precursors applying NH3-plasma and N2-plasma, respectively. The relative amount of O and N was determined by O1s and N1s XPS core level analysis. Our results indicate that samples prepared with TTIP are O-rich while with TDMAT are N-rich. In all films we identify different N species within the as-deposited films (Ti-N, Ti-ON, N2). [1]Surf. Coat. Technol. 205, 1287 (2010) [2]Biomaterials 23, 2835 (2002) [3]Microelectron. Reliab. 47, 752 (2007) [4]Thin Solid Films 442, 173 (2003) [5]Thin Solid Films 516, 6330 (2008) [6]J. Mater. Sci. Technol. 28, 512 (2012)

L.L II.8
17:30
Authors : M. Kodu, T. Avarmaa, H. M?ndar, R. Saar, R. Jaaniso
Affiliations : Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu, Estonia

Resume : Rear earth oxycarbonates are potential candidate materials for constructing simple and low cost chemiresistive sensors usable for monitoring level of carbon dioxide (CO2) gas in the living and working environment for personal comfort and health reasons. Also, measurement of CO2 concentrations is needed in many industrial processes. Specifically, Nd and La oxycarbonates in a form of nanoparticles have been studied previously as novel CO2 gas sensor materials. In this paper, pulsed laser deposition of La oxycarbonate (La2O2CO3) thin films was studied and structural properties of obtained thin films were characterized. Also, CO2 gas sensing ability of synthesized films was evaluated. The films deposited under CO2 partial pressure in various conditions were all Raman amorphous. In-situ or ex-situ annealing procedure at high CO2 partial pressure was needed for obtaining crystalline La2O2CO3 films, whereby hexagonal and monoclinic polymorphs were obtained in ex-situ and in-situ processes, respectively. Sensor structure, made using in-situ process, was sensitive to CO2 gas and showed relatively fast response and recovery characteristics.

L.L II.9
17:30
Authors : G. Socol1, S. Le Caër2, D. Craciun1, F. Oana1, A. C. Galca3, C. Martin4, V. Craciun1
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Măgurele, Romania; 2Institut Rayonnement Matière de Saclay, F-91191 Gif-sur-Yvette, France; 3National Institute for Materials Physics, RO - 077125, Măgurele-Bucharest, Romania; 4Ramapo College of New Jersey, NJ, USA

Resume : Thin-film transistors (TFTs) based on amorphous transparent and conductive oxides (a-TCOs) have been extensively studied in the last decade due to their higher mobility, improved uniformity and stability under bias stress compared to amorphous-silicon based TFTs. In addition, the amorphous layers could be manufactured at low temperatures on inexpensive and flexible substrates, which are also light weight. This opens the possibility for such devices to be used for space applications. There have been very few studies so far on the effect of radiation on a-TCOs structure and properties. We deposited amorphous indium zinc oxide thin films having different In/(In+Zn) compositions by the pulsed laser deposition technique at room temperature. After deposition, the films were submitted to gamma radiation from a 137Cs source up to a dose of 20 kGy (1 Gy = 1 J.kg-1) at a dose rate of 5 Gy/min under argon atmosphere. X-ray reflectivity and diffuse scattering investigations were performed to accurately measure the thickness and estimate changes induced by gamma radiation on the mass density and surface and interface roughness. Once the thickness of the films was known, spectroscopic ellipsometry and optical reflectivity investigations were used to assess changes induced by the irradiation on the optical and electrical properties of the films. Results showed that a-TCOs films could withstand the effect of gamma radiation with minimal changes of their electrical and optical properties.

L.L II.10
17:30
Authors : A. C. Galca1, G Socol2, L. M. Trinca1,3, and V. Craciun2
Affiliations : 1National Institute for Materials Physics, Atomistilor 105 bis, Magurele, Ilfov, Romania; 2National Institute for Lasers, Plasma and Radiation Physics, Atomistilor 409, Magurele, Ilfov, Romania; 3Faculty of Physics, University of Bucharest, Atomistilor 405, Magurele, Ilfov, Romania

Resume : Amorphous oxide semiconductors (AOS) based thin-film transistors (TFTs) have been extensively studied in the last decade due to their better optical and electrical properties compared to amorphous-silicon TFTs. There have been very few studies about their performance and reliability after thermal treatments. Amorphous indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) thin films having different cations compositions were obtained by the pulsed laser deposition (PLD) technique at room temperature on glass or Si substrates. The films were measured in-situ by employing spectroscopic ellipsometry and x-ray diffraction and reflectivity up to temperatures of 550° to obtain the optical constants (band gap, refractive index, absorption coefficient) and their dependence on temperature and structure.

L.L II.11
17:30
Authors : Gustavo H. Wegher, Emilson R. V. Junior, Jeferson F. de Deus
Affiliations : Department of Physics, Technological Federal University of Paraná

Resume : Carbon-based nanostructures, as carbon nanotubes (CNT), graphene (G) and graphene oxide (GO) have been extensively studied in the last years due to their unique electrical and optical properties. Recent research show that graphene can be used to improve the dispersion and stabilization of metal and metal-oxide nanostructures[1]. Titanium dioxide (TiO2) has been studied due to its non-toxicity, chemical stability and optoelectronic properties. However, the recombination of photoinduced electrons and holes limits its use on optoelectronic devices. To improve the charge separation efficiency of TiO2, much effort has been focused on TiO2 nanocomposites. In this work, thin films nanocomposites of graphene oxide (GO) and graphene oxide + TiO2 (GO-TiO2) were prepared using a alternative chemical route based on the Hummer’s method. The structural and chemical properties of the products were investigated using ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray power diffraction (XRD) and scanning electron microscopy (SEM). Several devices were built with both nanocomposites, GO and GO-TiO2. The impedance spectroscopy and resistivity measurements, using the van der Pauwn method, were done in order to determine the electrical properties of the material with and without the incorporation of TiO2. [1] A novel approach for synthesis of TiO2-graphene nanocomposites and their photoelectrical properties, Scripta Materialia, 64,621-624,2011.

L.L II.12
17:30
Authors : Ilaria Pallecchi 1, Francesca Telesio 1, Danfeng Li 2, Alexandre Fête 2, Stefano Gariglio 2, Jean-Marc Triscone 2, Alessio Filippetti 3, Pietro Delugas 4, Vincenzo Fiorentini 5, Daniele Marrè 1
Affiliations : 1 Department of Physics, CNR-SPIN and Genova University, via Dodecaneso 33, Genova 16146, Italy; 2 Department of Quantum Matter Physics, University of Geneva, 24 Quai E.-Ansermet, Geneva 4 1211, Switzerland; 3 CNR-IOM UOS Cagliari, c/o Dipartimento di Fisica, Universita` di Cagliari, S.P. Monserrato-Sestu Km.0,700, Monserrato (Ca) 09042, Italy; 4 CompuNet, Istituto Italiano di Tecnologia—IIT, Via Morego 30, Genova 16163, Italy; 5 Dipartimento di Fisica, Universita` di Cagliari, CNR-IOM, S.P. Monserrato-Sestu Km.0,700, Monserrato (Ca) 09042, Italy.

Resume : Understanding the nature of charge carriers at the LaAlO3/SrTiO3 interface is one of the major open issues in the full comprehension of the charge confinement phenomenon in oxide heterostructures. In particular, the existence localized levels at conduction band bottom has been hypothesized to explain the discrepancy between the observed charge carriers density in good quality samples [1] and the one predicted by polar catastrophe model [2] and several indirect evidences of their presence has been collected up to now. We will present the investigation of thermopower to study the electronic structure in LaAlO3/SrTiO3 at low temperature as a function of gate field. In particular, under large negative gate voltage [3], corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10^4–10^5 µV/K, oscillating at regular intervals as a function of the gate voltage. The huge thermopower magnitude can be attributed to the phonon-drag contribution, while the oscillations map the progressive depletion and the Fermi level descent across a dense array of localized states lying at the bottom of the Ti 3d conduction band. This study provides direct evidence of a localized Anderson tail in the two-dimensional electron liquid at the LaAlO3/SrTiO3 interface. [1] S. Thiel et al, Science 313, 1942 (2006). [2] A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004). [3] I. Pallecchi et al, Nat. Commun. 6, 6678 (2015).

L.L II.13
17:30
Authors : Liutauras Marcinauskas, Aleksandras Iljinas, Vytautas Stankus
Affiliations : Department of Physics, Kaunas University of Technology, Studentu str. 50, LT-51368 Kaunas, Lithuania

Resume : High quality lead titanate thin films were deposited using in situ layer-by-layer reactive magnetron sputtering. The optimal parameters were found in order to achieve the best structural quality of perovskite thin films without post annealing. Films were deposited on platinized silicon (Pt/Ti/SiO2/Si) substrates at 450-550 oC temperatures using Ti2O seed layer. It was shown that microstructure strongly depends on deposition temperature. The most dense and flat structures were formed at 550oC deposition temperature. Structural, morphological and ferroelectrical properties of thin films were investigated there. All thin films, deposited using seed layer, are highly texturized and nanocrystalline. Hysteresis measurements show that films exhibit ferroelectric properties with maximum coercive field of Ec=150 kV/cm and of Pr=60 C/cm2. Coercive field dependence on frequency measurements shows that creep regime of domain wall motions dominate till 1kHz frequency. Leakage current investigation shows that films exhibit the space charge limited conduction (SCLC), which in our case was higher due to the large concentration of oxygen vacancies.

L.L II.14
17:30
Authors : M. Hoffmann (1,2), S. K. Nayak (1), W. A. Adeagbo (1), K. L. Salcedo Rodríguez (3), C. E. Rodríguez Torres (3), Arthur Ernst (2) and W. Hergert (1)
Affiliations : (1) Martin Luther University Halle-Wittenberg, Institute of Physics, Von-Seckendorff-Platz 1, 06120 Halle, Germany (2) Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany (3) Departamento de Física, Facultad de Ciencias Exactas, C. C. 67, National University of La Plata, 1900 La Plata, Argentina

Resume : Cation site inversion and oxygen vacancy (Ovac) mediated ferromagnetic coupling between Fe spins, constitute two major physical mechanisms for the observed ferrimagnetism in ZnFe2O4 (ZFO) at room temperature. This conclusion is based on experimental results from x-ray magnetic circular dichroism measurements at the Fe L(2,3) edges and magnetization measurements performed on zinc ferrite nanoparticles and films, with different cation distributions and oxygen vacancy concentrations. Our density-functional-theory calculations indicate that the enhanced ferrimagnetic response observed in some nominally nonmagnetic or antiferromagnetic ferrites can be taken as a further example of the defect-induced magnetism phenomenon. We studied the magnetic coupling between the Fe ions in ZFO with and without Ovac. The formation energy of defects is used to analyze their stability in ZFO for the experimental growth conditions. The N\'eel temperature (TN) is determined from Monte Carlo simulations using the magnetic exchange interactions (Jij) obtained from first-principles method. The correlation energy is treated using GGA+U, where it is found that the Jij change almost linearly with increasing values of U. For TN comparable to the experimental results, the first neighbor interaction was small and positive as concluded from former experiments. With those Jij, the estimated temperature-dependent saturation magnetization is in good agreement with recent measurements.

L.L II.15
17:30
Authors : Sergejus Balčiūnas, Maksim Ivanov, Jūras Banys, Valentina Plaušinaitienė, Adulfas Abrutis
Affiliations : Faculty of Physics, Vilnius University, Sauletekio 9/3 817k., LT10222 Vilnius, Lithuania; Faculty of Physics, Vilnius University, Sauletekio 9/3 817k., LT10222 Vilnius, Lithuania; Faculty of Physics, Vilnius University, Sauletekio 9/3 817k., LT10222 Vilnius, Lithuania; Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania; Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania

Resume : Lithium tantalate is a well-known ferroelectric material, which also possesses piezoelectric, pyroelectric, nonlinear optic and acousto-optic properties. Its high Curie temperature (around 900 K depending on stoichiometry) makes all of its useful properties relatively insensitive to temperature changes. On the other hand, it is possible to use thin layers of the material to make a waveguide, which is controllable by acoustic and/or electric fields. All of this makes investigation of thin films of Lithium Tantalate an important topic with possible future applications. A study of dielectric properties of thin Lithium Tantalate-based films will be presented in this contribution. The films are deposited by pulsed injection chemical vapor deposition technique on a platinum layer on Si substrate. The grains of the films are columnar and make a textured structure. The measurements of the properties were performed in 100 K – 500 K temperature range and 100 Hz – 1 MHz frequency band. Analysis of the data is presented.

L.L II.17
17:30
Authors : A. Istrate, M. Danila, B. Bita, I. Mihalache, F. Comanescu, R. Plugaru, M. Purica
Affiliations : National Institute for R & D in Microtechnologies (IMT), Erou Iancu Nicolae Str. 126A, Bucharest 077190, Romania

Resume : Photocatalytic, sensing and light conversion performance of ZnO thin films are strongly affected by materials porous structure. The pores formation, distribution and size are proved to be tailored through films deposition in the presence of doping impurities as well as during post annealing treatments. In this work, thin films of ZnO doped with 5 at. % Mn and Ga have been prepared by sol-gel method starting from acetate and nitrate precursors, and spin coated on Si/SiO2 and glass substrates. The films were sequentially annealed at 500 oC in air for 1 h and at 500 oC in nitrogen or air for 2 h. The films structure, morphology, optical absorption/transmission and the refractive index have been assessed. All the films are polycrystalline, wurtzite type, and show preferential orientation along (002) direction. The crystallites size in the undoped films treated at 500 oC in air is about 22 nm, and decreases to 6 nm in Mn doped films and to 8 nm in Ga doped films. The treatment in nitrogen leads to crystallite size of 17 nm in undoped films, 5 nm and 8 nm in the films doped with Mn and Ga. The effect of thermal treatments on the films porosity have been analysed by spectroscopic ellipsometry. The porosity of the films treated in air is about 11% in the undoped films, 10% in the films doped with Mn and 22% in the films doped with Ga. After the second step of annealing performed in nitrogen, the porosity is 6% in undoped films and increases to 18% and 29% for Mn and Ga films.

L.L II.18
17:30
Authors : S. Brochen (1,2,3), M. Lafossas (1,2), I.-C. Robin (1,2), P. Ferret, F. Gemain (1,2), J. Pernot (1,3,4) and G. Feuillet (1,2)
Affiliations : 1 Univ. Grenoble Alpes, Inst. NEEL, F-38042 Grenoble, France 2 CEA-LETI, MINATEC Campus, 17 rue des Martyrs, F-38054 Grenoble Cedex 9, France 3 CNRS, Inst. NEEL, F-38042 Grenoble, France 4 Institut Universitaire de France, 103 boulevard Saint Michel, 75005 Paris, France

Resume : Whatever the growth deposition conditions or of the growth techniques, ZnO epilayers systematically exhibit n-type conductivity which seems to be sometime difficult to control. In this work, we have tried to determine the nature of the involved impurities in the electrical properties of ZnO thin films, grown by Metal Organic Vapor Phase Epitaxy (MOVPE) on sapphire and ZnO substrates. In both cases, secondary ion mass spectroscopy (SIMS) measurements give evidence for a strong diffusion of impurities from the substrate into the epilayer, especially for silicon and aluminum. In the case of samples grown on sapphire substrates, we observed on a wide growth temperature range (800°C-1000°C), an aluminum Fick’s diffusion profile into the epilayer. Furthermore, the effective dopant concentrations determined by capacitance-voltage measurements and compared to the SIMS impurity concentrations, highlights that both aluminum and silicon are responsible for the samples residual n-type doping. In addition, photoluminescence measurements confirmed the hydrogenic donor behavior of these two impurities. Thanks to all these experimental observations, ZnO thin films with a controlled n-type doping in the 1E16-1E19 cm-3 concentration range have been carried out. These results show that MOVPE growth is fully compatible with the achievement of highly doped thin films, but also with the growth of materials with low residual doping. [J. Appl. Phys. 115, 113508 (2014)]

L.L II.19
17:30
Authors : B. Kalska-Szostko*, U.Wykowska*
Affiliations : * Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Białystok, Poland

Resume : Nanomaterials can be obtained by many different ways: wet chemistry, organometallic reactions, ball milling, electrochemistry, sol-gel reactions, condensation, MBE sputtering, and so on. In many cases the properties of fine materials depend on the manner of fabrication procedure, their crystal structure, size, surface modification, solution composition, etc. [1]. One of the possible wires fabrication is electrodeposition method or thermal decomposition of elements in the anodic aluminum oxide (AAO). The process conditions such as temperature and composition of the used solution as well as current conditions determine matrix parameters (a pore diameter and center to center distance). In this presentation, it will be shown few very effective methods of magnetic nanowires preparation in AAO matrix, with various structure compositions. Such nanowires can possess core-shell, multilayered or alloy-like structure, and can be deposited in the matrix from selected elements. Obtained nanowires will be characterized by SEM. Structure of nanowires will be also examined by TEM and XRD, and magnetic properties will be analyzed by Mössbauer spectroscopy. [1] P. Christian, F. Von der Kammer, M. Baalousha, Th. Hofmann; Ecotoxicology 17 (2008) 326

L.L II.20
17:30
Authors : Mariusz Szkoda1, Katarzyna Siuzdak2, Katarzyna Grochowska2, Łukasz Skowroński3, Jakub Karczewski4, Anna Lisowska-Oleksiak1
Affiliations : 1Department of Chemistry and Technology of Functional Materials Chemical Faculty, Gdansk University of Technology Narutowicza 11/12, 80-233 Gdansk, Poland; 2Centre for Plasma and Laser Engineering The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Science Fiszera 14, 80-231 Gdansk, Poland; 3Institute of Mathematics and Physics, University of Technology and Life Sciences, Kaliskiego 7, 85-789 Bydgoszcz, Poland; 4Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland

Resume : Titanium dioxide is one of the most investigated metal oxides, which finds many applications i.a. in photocatalysis, solar cells, water splitting and batteries. In a significant amount of cases, the highly ordered TiO2 nanotube arrays are grown out of Ti metal plate during anodization process carried out in fluoride containing electrolyte. However, for practical some applications: solar cells or electrochromic windows, the semi-transparent TiO2 formed on the semi-transparent, conductive substrate is very much desired. In this work we show the ability to fabricate the semitransparent TiO2 nanotube arrays by varying anodization parameters including concentration and type of electrolyte (organic or inorganic), voltage and the bath temperature. The titanium thin film deposited onto the FTO substrate using gas injection magnetron sputtering (GIMS) method. The fabrication of Ti layer was performed in the vacuum chamber under Ar gas atmosphere (0.16 Pa). The substrate was not intentionally heated or cooled. The thickness of uniform Ti coating was estimated from a linear interface layer/substrate profile using the confocal optical microscope device and was found to be 1.97+/-0.01 um. The morphology of the nanostructured samples were investigated by Schottky field emission scanning electron microscopy and their absorbance ability was characterized using UV-vis spectrometer. Financial support from the National Science Center (2012/07/D/ST5/02269) is gratefully acknowledged.

L.L II.21
17:30
Authors : B. Kalska-Szostko*, U.Wykowska*, D. Satuła#
Affiliations : * Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Białystok, Poland #Department of Physics, University of Bialystok, Ciolkowskiego 1L, 15-245 Białystok, Poland

Resume : Recently, fabrication of nanomaterials attracts attention scientists from various research areas. Therefore, there are elaborated many different techniques of nanostructures preparation. Among others can be listed: MBE, sputtering, laser evaporation, electrochemistry, wet chemistry, etc. But always the easiest and cheapest methods are the best one form the economical point of view. That is why, porous aluminum oxide became very promising and popular, as a matrix to obtain various kind of nanowires by basic electrodeposition process [1]. Simplicity of the preparation of alumina matrixes, allows to obtain nanowires with desired thickness and length. There are few parameters which should be controlled to determine shape and depth of the pore: type of electrolyte, temperature, voltage, and time of anodization process. This way obtained matrixes can be used to deposit nanowires from both organic and inorganic solutions with variable internal structure. In this presentation we would like to show how conditions influences pores ordering and diameter, which reflect in the nanostructures organization and morphology. Techniques used for this studies are mainly SEM, TEM, and Mössbauer spectroscopy. [1] B. Kalska-Szostko, E. Brancewicz, P. Mazalski, J. Szeklo, W. Olszewski, K. Szymański, A. Sidor, Acta Physica Polonica A 119 (2009) 542-544

L.L II.22
17:30
Authors : K. Avramenko (1), S.V. Rarata (1,2), V. Strelchuk (1), V.P. Melnik (1) , P.Tronc (3), Chan Oeurn Chey(4), Magnus Willander(4)
Affiliations : 1) V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, pr. Nauky 41, 03028 Kyiv, Ukraine 2) Taras Shevchenko National University of Kyiv, 64 Volodymyrs’ka str., 01601 Kyiv, Ukraine 3)Centre National de la Recherche Scientifique, Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris, 10 rue Vauquelin, 75005 Paris, France 4)Physical electronics and nanotechnology division, department of Science and Technology, campus Norrkoping, Linkoping University, SE-60174 Norrkoping, Sweden

Resume : Investigation of diluted magnetic semiconductors has drawn considerable attention due to their further applications in a new generation of spintronic devices. Large-scale uniformly distributed ZnO hexagonal-shaped nanorods arrays with diameter ~450 to 600 nm were successfully synthesized by using the low temperature aqueous chemical growth method on glass substrate and then implanted with Mn+ ions to doses of 0.5∙1014, 2∙1014 and 3∙1014 cm−2 . After rapid thermal annealing (RTA) at 700 °C for 2 min, the optical properties of the RTA-Zn1-xMnxO NRs significantly improved due to compensation intrinsic defect centers VZn та Oi in matrix ZnO NRs. The observation of the E2(low), E2(high) -E2(low), E2(high) and A1(LO) modes in the Raman spectra confirms that ZnO NRs have hexagonal wurtzite structure. Implantation of Mn+ ions ZnO NRs leads to the formation of a solid solution Zn1-xMnxO and registration in micro-Raman spectra additional mode at 552 cm−1 which attributed to Zn-related vibration due to Mn incorporation. After RTA there is a significant improvement of the crystal quality of RTA- Zn1-xMnxO crystal lattice, which leads to an increase in intensity and reduction full-width at half maximum E2(low) and E2(high) modes. After annealing RTA- Zn1-xMnxO NRs A1(LO) mode reveals high frequency shift for 6 cm-1 compare to frequency Zn1-xMnxO NRs which explained increases the concentration of free carriers in the conduction band of Zn1-xMnxO NRs after compensated Mn2+-ion native charge defects ZnO that act as traps for free carriers.

L.L II.23
17:30
Authors : Kristin Bergum, Edouard Monakhov, Bengt Gunnar Svensson
Affiliations : University of Oslo, Centre for Materials Science and Nanotechnology

Resume : Cu2O is an interesting candidate for photovoltaic solar cells due to its suitable band gap, wide abundance, high absorption coefficient above the band gap, non-toxicity and affordability. The maximum theoretical efficiency of 20% is, however, currently far from being realized. There are still many challenges remaining, in particular in connection with the interface of the pn-junction of these solar cells. Defects present at the interface will both act as traps as well as affect the conduction band discontinuity. The highest efficiency cells (>5%) using the Cu2O/AZO (Al-doped ZnO) heterojunction have so far been achieved by inserting an n-type semiconductor material between the Cu2O and the ZnO layers. In this study we have investigated the effect of a buffer layer of TiO2 deposited by atomic layer deposition, between sputter-deposited Cu2O and AZO. Current-voltage (I-V) measurements show significant changes in the electrical behavior with changing TiO2 thickness. The Cu2O/ZnO heterojunction without TiO2 appears purely ohmic in behavior, however, with increasing TiO2 thickness, this behavior changes to an increasingly rectifying behavior. It is thus possible to tune some of the electrical behavior with buffer layer thickness, as will be further discussed in the full contribution.

L.L II.24
17:30
Authors : Tae Hoon Kang, Ho Young Jun, Si Ok Ryu*
Affiliations : School of Chemical Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan 712-749, South Korea

Resume : Zinc oxide(ZnO) is one of the versatile semiconducting materials due to its chemical and electrical properties such as resistivity control over the range 10-3 to 105 Ωㆍ㎝, transparency in the visible range, high-electrochemical stability, non-toxicity. Zinc oxide is also an attractive material with wide band gap (3.37 eV) and high excitation binding energy (60 meV) at room temperature. It has many potential applications in short-wave device, ultraviolet laser, thin-film gas sensor, solar cell, and wearable devices. In this study, various ZnO nano-structures including flower-like, chrysanthemum-like, tree-like as well as thin films were synthesized by a solution-based deposition method designed by a combination of a continuous flow reactor process and a spin coating method, and then they were characterized to investigate the influences of the processing parameters on the performance of ZnO. XRD, SEM, EDX, UV-vis Spectroscopy, and XPS were employed in the characterization of the prepared structures and films. Based on the characterization, it was found that flow rate, annealing temperature, pH, reaction time, and precursor concentration exerted an effect on the properties of ZnO. We have also fabricated thin film transistors (TFT) using ZnO thin films through the CFR-spin coating process. The Al/ZnO/SiO2/Si/Au structure was used for fabrication of bottom gate metal-insulator-semiconductor-field-effect-transistor (MISFET) device and more in depth investigations are in progress.

L.L II.25
17:30
Authors : Alexander Sherstnyov, Stanislau Niauzorau, Kseniya Girel, Sergey Redko, Eugene Chubenko, Vitaly Bondarenko
Affiliations : Belarusian State University of Informatics and Radioelectronics, P. Brovka str. 6, Minsk 220013, Belarus

Resume : In this paper we investigated the optical properties of porous silicon (PS) templates with electrochemically deposed zinc oxide (ZnO). PS templates were formed by electrochemical anodization in pulsed galvanostatic mode in darkness and by the metal assisted chemical etching (MACE). ZnO electrochemical deposition into PS was carried out in dimethylsulfoxide based solutions containing 0.03 M ZnCl2 and 0.1 M KCl, and polyoxyethilene (POE) and H2O2 as additives During 60 min of deposition separate ZnO nanoparticles formed inside PS layer. It was shown that ZnO nanoparticles size depends on the deposition current density. After annealing at 500 °C on air samples with ZnO deposited into electrochemically formed PS template demonstrated intense photoluminescence (PL) emission peaks around 570 and 650 nm associated with recombination via oxygen defects related energy levels in ZnO bandgap. PL spectra of ZnO/PS samples formed by MACE cover visible and near-IR range (from 420 nm to 900 nm) and represent combination of PL bands related to deep-level defect in ZnO and PL bands of silicon nanowires. Obtained ZnO/PS composite nanostructures can be used in perspective white light-emitting devices.This research is supported by the Grant of Ministry of Education of Republic of Belarus for students, and Belarus Government Research Programs “Nanothechnology and nanomaterials”, grant 2.4.16; “Electronics 2015”, grant 1.1.14.

L.L II.26
17:30
Authors : Mohamad M Ahmad, H. Mahfoz Kotb, Abdullah Al-Jaafari, Koji Yamada
Affiliations : Department of Physics, College of Science, King Faisal University, Al-Ahsaa 31982, Saudi Arabia; Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575, Japan

Resume : Materials with high values of the dielectric constant are technologically important in high energy density storage and microelectronics applications. Giant dielectric constant (GDC) > 10000 was discovered in the perovskite family of ACu3Ti4O12 (ACTO) materials (A = Ca, La2/3, Y2/3, Bi2/3, Na0.5Bi0.5, etc). The observed GDC is due to internal barrier layer capacitance (IBLC) effects that originate from the presence of semiconducting grains surrounded by resistive grain boundaries. ACTO ceramics are usually prepared by solid state reaction followed by conventional sintering at high temperatures for several hours. This process leads to substantial grain growth, and the value of the dielectric constant was found to increase with increasing the grain size from few to hundreds m. Here, we present our results on the mechanosynthesis at RT and spark plasma sintering (SPS) at different temperatures of different ACTO ceramics. The characteristics of the SPS technique led to minimal grain growth, and nanoceramics of ACTO with grain size of 100 – 450 nm were obtained. ACTO nanoceramics have GDC of similar values as conventionally sintered micro-sized ceramics. The electrical properties of the current materials, which were studied by impedance spectroscopy measurements, show that the grains are semiconducting with a conductivity value of ~ 0.01 S/cm at RT, whereas the conductivity of the grain boundaries is several orders of magnitude smaller, which confirm the IBLC origin of the GDC.

L.L II.27
Start atSubject View AllNum.
 
Oxide thin films: Fundamentals I : Jeroen van den Brink (Room 328, MINI building)
09:00
Authors : N Bogdanov, V Katukuri, J Romhanyi, V Kataev, B Buechner, J van den Brink, and L Hozoi
Affiliations : IFW Dresden, Germany

Resume : A promising route to tailoring the electronic properties of quantum materials and devices rests on the idea of orbital engineering in multilayered oxide heterostructures. In this context, we identify and discuss in detail one simple mechanism for adjusting the sequence of d-electron energy levels: interplanar ionic charge imbalance along successive metal-oxygen layers. Through interplay with distortions of the ligand cages, it provides a knob for tunning the ordering of electronic levels in even intrinsically stacked oxides. We analyze in this regard electron spin resonance data on the 214 Sr-iridate oxide compound. While canonical ligand-field theory predicts z-axis g factors smaller than 2 for positive tetragonal distortions as present in Sr214, the experiment indicates values >2. This implies that the iridium d levels are inverted with respect to their normal ordering. State-of-the-art quantum chemistry calculations confirm the level switching in Sr214, whereas we find them to be instead normally ordered in the sister compound Ba214. Given the nonpolar character of the metal-oxygen layers, our findings highlight the tetravalent transition-metal 214 oxides as ideal platforms to explore d-orbital reconstruction in the context of oxide electronics. The role of internal anisotropic fields related to the environment beyond nearest-neighbor ligands is further addressed by means of ab initio quantum chemistry calculations for 3D pyrochlore compounds.

L.10.1
09:30
Authors : Wojciech Brzezicki, Canio Noce, Alfonso Romano, Andrzej M. Oles, Mario Cuoco
Affiliations : CNR-SPIN and Dipartimento di Fisica 'E.R. Caianiello', Università di Salerno, I-84084 Fisciano (Salerno), Italy; CNR-SPIN and Dipartimento di Fisica 'E.R. Caianiello', Università di Salerno, I-84084 Fisciano (Salerno), Italy; CNR-SPIN and Dipartimento di Fisica 'E.R. Caianiello', Università di Salerno, I-84084 Fisciano (Salerno), Italy; Marian Smoluchowski Institute of Physics, Jagellonian University, prof. S. Łojasiewicza 11, PL-30348 Kraków, Poland; CNR-SPIN and Dipartimento di Fisica 'E.R. Caianiello', Università di Salerno, I-84084 Fisciano (Salerno), Italy

Resume : The entanglement of spin, orbital and lattice degrees of freedom in correlated systems is known to lead to intricate quantum phenomena [1]. Correlated physics in transition metal oxides traditionally emphasizes 3d materials because more extended 4d-shells would a priori suggest a weaker ratio between intra-atomic Coulomb interaction and electron bandwidth. Nevertheless, these 4d-oxides have a tendency to distort so the change in M-O-M bond angle can narrow the d-bandwidth, bringing the system on the verge of a metal-insulator transition or into an insulating state. The interplay between more localized 3d and more delocalized 4d states tunes the competition between correlated metallic and Mott-insulating states with spin-orbital-lattice degrees of freedom. In this framework, we study how magnetic and orbital patterns in a uniform 4d host are modified by inclusion of 3d impurities substituting 4d ions. After discussing the most suitable microscopic models for different types of 3d-4d hybrids, we determine phase diagrams assuming different conditions for orderings, both for metallic [2] and insulating cases [3]. We demonstrate that coupling between impurity and host, specific of the 3d-4d elements (here Mn and Ru), can generate a complex phase competition [2-3]. [1] A.M. Oleś, J. Phys.: Condensed Matter 24, 313201 (2012). [2] W. Brzezicki, C. Noce, A. Romano, M. Cuoco, arXiv:1411.1952 (accepted in PRL) [3] W. Brzezicki, A. M. Oleś, and M. Cuoco, Phys. Rev. X 5, 011037 (2015).

L.10.2
09:45
Authors : Dmitri Efremov, Beom Hyun Kim, Vamshi M. Katukuri, Klauss Koepernik, and Jeroen van den Brink
Affiliations : IFW Dresden, Dresden, Germany

Resume : Ir-based double perovskite with 5d4 electronic configuration are considered to have a non-magnetic ground state (J = 0 with L =1 and S=1). However, recently long-range antiferromagnetic order was reported for Sr2YIrO6. It was argued that it is originated from the highly distorted IrO6 octahedra. In this talk we will discuss Ba2YIrO6, which has similar electron configuration 5d4 of Ir atoms, but has a cubic structure. It will be shown that in the frame of LDA+U theory with U =1.4eV the ground state is nonmagnetic insulating with a gap 0.6 eV in agreement with experimental data on transport, magnetization and specific heat. Further we will discuss magnetic excitations in terms of bond- bosons and conditions for their possible condensation. The results will be compared with the recent RIXS results.

L.10.3
10:00
Authors : D. Stornaiuolo 1, G. M. De Luca 1, R. Di Capua 1, E. Di Gennaro 1, F. Miletto Granozio 1, G. Ghiringhelli 2, I. Pallecchi, D. Marrè 3, C. Piamonteze 4, S. Rusponi 5, C. Cantoni, and M. Salluzzo 1
Affiliations : 1 CNR-SPIN and University Federico di Napoli (Italy) 2 Politecnico di Milano (Italy) 3 CNR-SPIN and University of Genova (Italy) 4 C. Piamonteze PSI-SLS (Switzerland) 5 EPFL (Switzerland) 6 Oak Ridge National Labs (USA)

Resume : The quasi two-dimensional electron gas (q2DEG) created at the interface between LaAlO3 and SrTiO3 shows several intriguing properties, including an inversion of the Ti3d bands hierarchy at the interface respect the bulk [1], large Rashba spin-orbit coupling [2], and even coexistence between magnetism and superconductivity [3-4]. The occurrence of a magnetic ground state at the interface of non-magnetic oxides, in particular, raised a great interest. However, its intrinsic origin at the LAO/STO interface remains debated [5-6]. In this work, we show that an electric field tunable spin-polarized and superconducting q2DES can be created in LAO/STO heterostructures by introducing few atomic delta doping layers of EuTiO3. The spin-polarized character of the Ti-3d bands is demonstrated by x-ray absorption spectroscopy and by longitudinal and Hall effect transport data as function of a gate voltage. Our experimental data are condensed in a phase diagram showing that, in a large range of carrier density, superconductivity (SC) sets-in from a ferromagnetic (FM) normal state. [1] M. Salluzzo, et al., Phys. Rev. Lett. 102, 166804 (2009) [2] A. D. Caviglia, et al., Phys. Rev. Lett. 104, 126803 (2010) [3] L. Li, C. Richter, Nature Physics 7, 762 (2011) [4] J. A. Bert, et al., Nature Physics 7, 767 (2011) [5] J. S. Lee, et al., Nat Mater 12, 703 (2013) [6] M. Salluzzo, et al., Phys. Rev. Lett. 111, 087204 (2013)

L.10.4
10:30 Coffee break    
 
Oxide thin films: Fundamentals II : Susanne Hoffmann-Eifert (Room 328, MINI building)
11:00
Authors : Roser Valenti
Affiliations : Institute of Theoretical Physics Goethe University Frankfurt 60438 Frankfurt Germany

Resume : Motivated by recent ARPES and SARPES experiments on the observation of a two-dimensional electron gas (2DEG) at the surface of SrTiO3 [1,2] as well as a giant spin-splitting on the 2DEG [3], we discuss in this talk the role of oxygen vacancies, magnetism and spin-orbit coupling based on ab initio calculations and model considerations on SrTiO3 slabs [4,5]. This work is in collaboration with M. Altmeyer, H.O. Jeschke, O. Hijano, C. Martins, M. Rozenberg, A. Santander-Syro and M. Gabay [1] A. Santander-Syro et al. Nature 469, 189 (2011) [2] W. Meevasana et al. Nature Materials 10, 114 (2011) [3] A. Santander-Syro et al. Nature Materials [4] H.O. Jeschke, J. Shen, R. Valenti, New J. Phys. 17 023034 (2015) [5] M. Altmeyer et al. (in preparation)

L.11.1
11:30
Authors : Bronisław Psiuk, Jacek Szade, Krzysztof Szot
Affiliations : Institute of Ceramics and Building Materials, Department of Refractory Materials, Toszecka 99, 44-100 Gliwice, Poland; University of Silesia. A. Chełkowski Institute of Physics, Uniwersytecka 4, 40-007 Katowice, Poland; Research Center Jülich GmbH, Institute of Solid State and CNI – Center of Nanoelectronic Systems for Information Technology, 52425 Jülich, Germany

Resume : With the use of X-ray Photoelectron Spectroscopy we studied segregation processes occuring in the vicinity of the SrTiO3 (100) single crystal surface induced by low energy Ar+ ion etching. We confirm that selective etching and formation of titanium oxides with lower oxidation states is responsible for the insulator-metal transition. However, photoemission data indicate interesting effect that after exposition of the treated sample to air the SrO insulating complexes are shifted towards the top. In addition, it was shown that the process of conductive layer formation is less effective when ion etching of the crystal is provided at an elevated temperature. It is explained by the enhanced oxygen diffusion rate and the process of self oxidation in the heated sample.

L.11.2
11:45
Authors : A. Albar, H. A. Tahini, U. Schwingenschlögl
Affiliations : king abdullah university of science and technology

Resume : Device applications of transparent conducting oxides require a thorough understanding of the physical and chemical properties of the involved interfaces. We use ab-initio calculations within density functional theory to investigate the electronic states at the SnO/SnO2 heterointerface. Tin dioxide and monoxide are transparent materials with high n-type and p-type mobilities, respectively. This work aims at exploring the modifications of the electronic states, in particular the charge transfer, in the vicinity of the heterointerface. The (110) interface is modeled by a supercell approach in order to minimize the mismatch between the lattice parameters of the two compounds. We discuss the electronic density of states as a function of the distance to the interface.

L.11.3
12:00
Authors : Susanne Stemmer
Affiliations : Materials Department, University of California, Santa Barbara, CA 93106-5050, USA

Resume : Understanding the anomalous transport properties of strongly correlated materials in proximity to a quantum phase transition present a significant challenge. For example, in the normal state of unconventional superconductors one encounters deviations from Fermi liquid behavior, longitudinal and Hall scattering rate separation, a pseudogap phase, and bad metal behavior. These properties have been studied extensively in bulk materials. Here we show that oxide heterostructures allow for additional tuning and control, using dimensionality, electrostatic doping, and interface effects to introduce (proximity to) magnetic order. We will discuss emergent phenomena in two-dimensional electron liquids formed at the interface between Mott insulating rare earth titanates and the band insulator SrTiO3. Such interfaces exhibit a high-density, two-dimensional electron liquid, of approximately ½ electron per surface unit cell, providing ~ 3×1014 cm-2 mobile charge. Narrow quantum wells embedded between two such interfaces allow for extremely high mobile carrier densities and the emergence of phenomena typical of strongly correlated systems. We will discuss metal-insulator transitions, the conditions for the appearance of non-Fermi liquid exponents in the temperature dependence of the resistivity, transport lifetime separation, and the relation to the proximity to different types of magnetism and a quantum critical point.

L.11.4
12:30 Lunch break    
 
2DEGs at oxide interfaces : Susanne Stemmer (Room 328, MINI building)
14:00
Authors : M. Sing, J. Gabel, P. Scheiderer, P. Schuetz, M. Zapf, L. Dudy, F. Pfaff, G. Berner, O. Kirilmaz, R. Claessen, H. Fujiwara, A. Sekiyama, A. Yamasaki, S. Suga, Y. Saitoh, Y.Z. Chen, N. Pryds, M. Gorgoi, V. Rogalev, V.N. Strocov, J.D. Denlinger, C. Schlueter, T.-L. Lee
Affiliations : Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg, Wuerzburg, Germany; Osaka University, Graduate School of Engineering Science, Osaka, Japan; Konan University, Faculty of Science and Engineering, Kobe, Japan; Osaka University, Institute of Scientific & Industrial Research, Osaka, Japan; Japan Atomic Energy Agency, Condensed Matter Science Division, SPring-8, Hyogo, Japan; Technical University of Denmark, DTU Energy Conversion, Riso DTU campus, Denmark; Helmholtz Zentrum Berlin fuer Materialien und Energie GmbH, Berlin, Germany; Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland; Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, USA; Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, United Kingdom;

Resume : The interfaces of complex oxide heterostructures can host novel quantum phases not existing in the bulk of the constituents, with the high-mobility 2D electron system (2DES) in LaAlO3/SrTiO3 (LAO/STO) representing a prominent example. Despite extensive research the origin of the 2DES and its unusual properties - including the coexistence of superconductivity and ferromagnetism - are still a matter of intense debate. Photoelectron spectroscopy in the hard (HAXPES) and also the soft (SX-(AR)PES) X-ray regime has proven to be a powerful method to provide detailed insight into the electronic structure of these heterostructures and, in particular, of the buried interface. This includes the identification of the orbital character of the 2DES as well as the determination of vital band structure information such as band alignment and band bending, and even k-resolved band dispersions and Fermi surface topology. Moreover, resonant photoemission at the Ti L-edge reveals the existence of two different species of Ti 3d states, localized and itinerant, which can be distinguished and identified by their different resonance behavior. Controlled in situ oxidation allows us to vary the oxygen composition from fully stoichiometric to strongly O-deficient and thereby the amount of localized and itinerant Ti 3d electrons. By comparison to free STO surfaces we can thus demonstrate that the metallicity of the heterointerfaces is intrinsic, i.e., it persists even in the absence of O defects. I will discuss our photoemission results on LAO/STO heterostructures in both (100) and (111) orientation as well as on the related system gamma-Al2O3/STO(100), which also hosts a 2DES with even higher electron mobility.

L.12.1
14:30
Authors : Carsten Woltmann [1], Dr. Rainer Jany [2], Dr. Christoph Richter [1-2], Dr. Hans Boschker [1], Prof. Dr. Jochen Mannhart [1]
Affiliations : [1] Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany; [2] Experimental Physics VI, Augsburg University, 86159 Augsburg, Germany

Resume : Since scaling of conventional semiconductor devices is becoming increasingly difficult, a quest for functional materials that complement Si-CMOS technology has begun. The broad array of extraordinary electronic properties makes complex oxides a compelling arena for possible new devices and a fascinating field of fundamental research. The fabrication of functional sub-micrometer devices using complex oxide heterostructures bears new challenges to thin film growth as well as patterning techniques. Here, we report on field effect devices with gate lengths as small as 50nm. The drain source channels are provided by the electron liquid generated at the LaAlO3-SrTiO3 interface. The fabrication process of these devices, characteristic changes in electronic transport properties with shrinking gate lengths (short channel effects), and their integratability will be discussed.

L.12.2
14:45
Authors : E. Di Gennaro,1, A. Safeen,1 U. Coscia,2 G. Ambrosone,1 A. Khare,1 F. Miletto Granozio,1 and U. Scotti di Uccio1
Affiliations : 1 Dipartimento di Fisica, Univ. di Napoli Federico II and CNR-SPIN, Compl. Univ. di Monte S. Angelo, Via Cinthia I-80126 Napoli (Italy); 2 Dipartimento di Fisica, Univ. di Napoli Federico II and CNISM Unità di Napoli, Compl. Univ. di Monte S. Angelo, Via Cinthia I-80126 Napoli (Italy)

Resume : Oxide interfaces exhibit sometimes functionalities that are totally new with respect to those of their constituent materials. A prototypical example of this emergent behaviour is provided by the 2-dimensional electron gas (2DEG) first found at the LaAlO3 /SrTiO3 interface. In this study, we investigate the formation of 2DEG in different epitaxial interfaces, comparing their properties with those of their amorphous counterparts, which also exhibit a highly mobile electron gas. A number of experiments have been designed and performed with the specific aim of highlighting similarities and differences between two kind of interfaces. In particular, time-resolved photoconductance of amorphous and crystalline LaAlO3 /SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3 /SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3 . This second channel is less relevant in amorphous LaAlO3 /SrTiO3 , where the higher density of point defects plays instead a major role.

L.12.3
15:00
Authors : Akif Safeen, E. Di Gennaro, Alessia Sambri, U. Scotti di Uccio, F. Miletto Granozio
Affiliations : CNR-SPIN, Department of Physics, University of Naples "Federico II” Naples, Italy

Resume : Recently, the transport properties of the two-dimensional electron gas (2DEG) formed at LaAlO3/SrTiO3 interfaces 1-2-3-4 has been intensively investigated and compared to that hosted by similar structures (e.g., -Al2O3/SrTiO3)5. In particular, it was demonstrated that light can effectively enhance the carrier density, and that this effect is persistent after turning off the illumination. Another established technique to modify the carrier density relies on the fabrication of three terminal devices, where positive/ negative gating voltages respectively determine the filling/ depletion of the quantum well6. In this study we considered several 2DEGs formed at oxide heterostructures, including crystalline LaAlO3/SrTiO3 and -Al2O3/SrTiO3. We investigated both the photoconductance and the field-effect dynamics with the aim of clarifying some details of the electronic structure and of the electronic transport. Our data of photoconductivity under illumination with different wavelengths and intensity allow some considerations on the nature and distribution of the defects that are excited by the light. Complementary considerations also stem from the field effect. Furthermore, we observed in these measurements a hysteretic behavior under gating voltage that we ascribe to a ferroelectric state of SrTiO3, with some clear anomalies near the ferroelastic and the quantum-paraelectric transition temperature. References 1. A. Ohtomo , H. Y. Hwang , Nature 2004 , 427 , 423 – 426 2. Enrico Traversa et.al, ACS Nano 2012 , 6 , 1278 – 1283 . 3. E. Di Gennaro et.al, Adv. Optical Mater. 2013. 4. S. Thiel et. Al, Science 313, 1942 (2006). 5. Chen. Y. Z. et al. Nat. Commun. 2394 (2013). 6. Sze, S. M. & Ng, K. K. Physics of Semiconductor Devices 3rd edn (John Wiley, 2007).

L.12.4
15:15
Authors : Kristy J. Kormondy,1 Agham B. Posadas,1 Thong Q. Ngo, 2 Sirong Lu,3 Nicholas Goble,4 Jean Jordan-Sweet,5 Xuan P. A. Gao,4 David J. Smith,3 Martha R. McCartney, 3 John G. Ekerdt,2 and Alexander A. Demkov1
Affiliations : 1 Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA; 2 Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA; 3 Department of Physics, Arizona State University, Tempe, Arizona, 85287, USA; 4 Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA; 5 IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA

Resume : A highly interesting application for SrTiO3 involves the formation of a high mobility two-dimensional electron gas (2DEG) at the oxide/oxide interface. We report on the conducting layer formed at the crystalline γ-alumina/SrTiO3 (STO) interface which is attributed to oxygen vacancies. We describe the structure of thin γ-alumina layers deposited by molecular beam epitaxy on STO (001), as determined by reflection-high-energy electron diffraction, x-ray diffraction, and high-resolution electron microscopy. In-situ x-ray photoelectron spectroscopy was used to confirm the presence of oxygen vacancies at the interface. Electrical characterization indicates a higher sheet resistance for lower deposition temperature. A maximum electron Hall mobility of 3100 cm2V-1s-1 at 3.2 K and room temperature mobility of 22 cm2V-1s-1 are measured.

L.12.5
15:30 Coffee break    
 
Advanced characterization of oxide thin films and interfaces : Fabio Miletto-Granozio (Room 328, MINI building)
16:00
Authors : N. Gauquelin, Y.Z. Chen, D. Samal, Z. Liao, R. Egoavil, N. Pryds, G. Koster, J. Verbeeck, G.Van Tendeloo
Affiliations : N. Gauquelin,R. Egoavil,J. Verbeeck, G.Van Tendeloo: EMAT, Department of physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium Y.Z. Chen,N. Pryds: Department of Energy Conversion and Storage, Technical University of Denmark, Risø Campus, 4000 Roskilde, Denmark. D. Samal, Z. Liao,G. Koster: MESA+ Institute for Nanotechnology, University of Twente, PO.BOX 217, 7500 AE, Enschede, The Netherlands

Resume : The increasing miniaturization of electronic devices and the atomic understanding of physical and chemical phenomena like superconductivity and two-dimensional electron gases are increasing the need for reliable imaging and spectroscopy at the atomic level. Here we present several examples of on-going research in the area of advanced functional materials and interfaces such as (SrCa)CuO2 stacked with SrTiO3, SrRuO3 or BaCuO2 layers, non-crystalline LaAlO3 on SrTiO3 with a (LaSr)MnO3 interlayer and (La,Sr)MnO3 on NdGaO3 (with or without an SrTiO3 buffer layer) to emphasize the key role played by aberration-corrected electron microscopy (EM) in the arsenal of techniques necessary for materials development and characterization. Heavy atoms can be imaged with high-angle annular dark-field Scanning Transmission EM (HAADF-STEM) and light elements such as oxygen can be accessed through annular bright-field imaging (ABF-STEM). Combining these two techniques, atomic displacements and octahedral tilts which have a major influence on the rise of new physical properties in heterostructures can be accessed rather easily. In addition, the electronic structure changes related to strain, orbital and interfacial engineering as well as surface termination are accessible in the fine structure of EELS core-loss edges which can provide bonding and valence states, providing a deep understanding of the electronic structure, at the heart of the fascinating properties observed in these compounds.

L.13.1
16:30
Authors : Hicham ZAID (1), Marie-Hélène BERGER (1), Denis JALABERT (2), Michael WALLS (3), Richard AKROBETU (4), Alp SEHIRLIOGLU (4), Nicholas GOBLES (5), Xuan GAO (5), Pascal BERGER (6)
Affiliations : (1) Mines ParisTech, Centre des Matériaux, UMR CNRS 7633, BP 87, 91003 Evry, France ; (2) CEA-INAC/UJF-Grenoble 1 UMR-E, SP2M, LEMMA, Minatec Grenoble F-38054, France ; (3) Laboratoire de Physique des Solides, Université Paris Sud, Bât 510, 91405 Orsay, France ; (4) Departments of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio, USA ; (5) Departments of Physics, Case Western Reserve University, 10900 Euclid Ave., Cleveland, Ohio, USA ; (6) CEA/DSM/IRAMIS/SIS2M, CEA-Saclay, F-91191 Gif sur Yvette, France

Resume : Heterostructures made of SrTiO3 and LaAlO3 exhibit a two-dimensional electron gas at the interface. This work aims to develop a comprehensive approach to investigate the origin of the charge carriers in oxide based hetero-interfaces. Several mechanisms have been proposed to explain this behavior, such as the polar catastrophe at the polar LaAlO3/non-polar SrTiO3 interface, structural distortions, oxygen vacancies, preferential cationic intermixing at the interface or film stoichiometry. An analytical tool with a depth resolution below the cell dimension (~0.4 nm) is required to assess the role of strain and intermixing on 2DEG. Non-destructive method Medium-Energy Ion Spectroscopy (MEIS) offers this depth resolution. For the first time, the chemical and strain profiles near the LaAlO3/SrTiO3 hetero-interfaces have been quantified and correlated. Conductive and insulating samples have been synthetized by Pulsed-Laser Deposition in different growth conditions to discriminate each of the above mechanisms. Intermixing and structural distortions are revealed for conductive and insulating samples. Intermixing is more pronounced in thicker film samples whereas compressive strains are more extended is thinner ones. These results have been coupled with EELS analyses to determine the influence of electron reconstruction and oxygen vacancies on charge carrier densities.

L.13.2
16:45
Authors : D. Di Castro, C. Cantoni, C. Aruta, A. Tebano, N. Yang, G. Balestrino
Affiliations : Dipartimento di Ingegneria Civile e Ingegneria Informatica, Universita' di Roma Tor Vergata, Via del Politecnico 1, I-00133 Roma, Italy; CNR-SPIN, Universita' di Roma Tor Vergata, Roma I-00133, Italy; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6116, USA; Facolta' di Ingegneria, Universita' degli studi Niccolo' Cusano, Rome I-00166, Italy;

Resume : The interface between complex transition metal oxides is emerging as one of the most interesting systems in condensed matter physics. Indeed, a variety of new and unusual electronic phases, as high mobility 2D electron gas, quantum Hall effect, and interface superconductivity, have been discovered. At the interface between the insulating infinite layer CaCuO2 (CCO) and the insulating perovskite SrTiO3 (STO), high Tc superconductivity shows up. This happens only when the interface between the Ca plane of CaCuO2 and the TiO2 plane of SrTiO3 is realized, by growing, with pulsed laser deposition, the heterostructure CCO/STO on NdO terminated substrate. Indeed, by using state-of-the-art aberration-corrected scanning transmission electron microscopy (STEM) coupled to electron energy loss spectroscopy (EELS), we show that only for this kind of interface extra oxygen ions can be incorporated in the interface Ca plane, providing holes to the CuO2 planes lying below. Thanks to the unprecedent STEM/EELS spatial resolution, we obtain a detailed spatial profile of the holes introduced at the interface by the excess oxygen ions. The holes concentration decays suddenly after 1-2 CCO unit cells from the interface with STO, giving rise to a quasi-2D (super)conductivity. Given the structural peculiarity of the CCO/STO interface, the obtained results can be extended to multilayered high Tc cuprates.

L.13.3
17:00
Authors : Andrea Gerbi, Renato Buzio, Alessandro Gadaleta, Luca Anghinolfi, Michael Caminale, Emilio Bellingeri, Antonio Sergio Siri, Daniele Marr?
Affiliations : A. Gerbi; R. Buzio, A. Gadaleta, M. Caminale, E. Bellingeri; A. S. Siri; D. Marr? CNR-SPIN Institute for Superconductors, Innovative Materials and Devices, C.so Perrone 24, 16152 Genova, Italy; A. Gadaleta; M. Caminale; A. S. Siri; D. Marr? Physics Department, University of Genova, Via Dodecaneso 33, 16146 Genova, Italy; L. Anghinolfi Paul Scherrer Institut 5232 Villigen , Switzerland.

Resume : Nanometer-scale alterations of the Schottky barrier represent one of the microscopic mechanisms proposed to explain the resistance switching in transition-metal oxide cells. We report on novel Ballistic Electron Emission Microscopy (BEEM) experiments aimed to directly visualize and quantify the local inhomogeneities of the effective Schottky barrier height on Au/Nb:SrTiO3 Schottky junctions dominated by interfacial resistance switching effects [1]. The low Schottky Barrier Height (SBH) regions observed in our BEEM data, can be associated to the electron transport through spatially-localized defects of nanometric size in the interfacial layer. The same value has been observed also for the ON state in the macroscopic current-coltage (I?V) curves of the device. Outside the nanometric regions with low SBH, most of the interface of the diode is dominated by a higher value of the Schottky barrier in good agreement with the value extracted by our I?V curves in air and with the SBH observed in the OFF state. The voltage-dependent variation of the local barrier height of the nanometric patches could explain the non-ideal behaviour of the resistance switching effects [2]. [1] Andrea Gerbi , Renato Buzio , Alessandro Gadaleta , Luca Anghinolfi , Michael Caminale , Emilio Bellingeri , Antonio Sergio Siri , and Daniele Marr? Adv. Mater. Interfaces (2014), 1300057 [2] R. Buzio , A. Gerbi , A. Gadaleta , L. Anghinolfi , F. Bisio , E. Bellingeri , A. S. Siri , D. Marr? , Appl. Phys. Lett. (2012) , 101 , 243505

L.13.4
17:15
Authors : Juris Purans
Affiliations : Institute of Solid State Physics University of Latvia

Resume : Engineering of new mixed transition metal (TM:TM) oxides based electronic thin films for industrial applications is impossible without detailed knowledge of the atomic and electronic structure of these materials and the processes on the atomic level. X-ray Absorption Fine Structure (XAFS) spectroscopy is extremely suitable technique to study the local atomic and electronic structure of mixed nanocrystalline and amorphous thin films. The dependence of thin films local structure on composition, probed with subpicometer accuracy, and new possibilities of XAFS data analysis will be presented for the intercalated transition metal (TM:TM) oxides: cathodic (WO3, MoO3, ReO3, TiO2, etc.) and anodic (NiOx, IrOx, etc.). The electrochromic properties and catalytic reactivity of the TM:TM oxides are strongly structure-sensitive. XAFS spectra were measured at the both absorption edges of mixed TM:TM oxides (W, Re, Ir, Ta, Ce L-edges and Mo, Ni. Ti K-edges) at the synchrotron radiation beam lines. With this complementary data on the local structure it is possible to give a better view on the electronic structure and distribution of the two ions in thin films.

L.13.5
18:00 Best Student Presentation Awards Ceremony and Reception (Main Hall)    
Start atSubject View AllNum.
09:00 Plenary Session - Main Hall    
12:30 Lunch break    
 
Oxide thin film growth : Valentin Craciun
14:00
Authors : N. Hildenbrand, J.M. Dekkers, A. Janssens
Affiliations : SolMateS B.V.

Resume : New materials are required in order to meet upcoming technology nodes or to progress ?beyond Moore?. It is well known that Pulsed Laser Deposition (PLD) is a very flexible and versatile technique allowing fast optimization of new thin film materials. Moreover PLD is superior above other deposition technologies for the stabilization of volatile elements and nucleation of complex oxide material systems. However, mainly because of the sample size, the developed materials and processes in PLD research tools only just make it into demonstrator devices. In order to make it into commercial applications, next generation PLD equipment is needed to bridge the gap between demonstrator and the prototype ? pilot ? production stages. The new SolMateS? R&D platform is the next step beyond fundamental (PLD) research. The reliable hardware is flexible for fast process optimization and allows uniform thin film deposition up to 200 mm diameter with high reproducibility. The automated software ensures easy operation and stable performance. The small footprint makes it very easy to attach it to an existing PLD beam path in the research facility. Since process recipes can be transferred directly to SolMateS? PLD production equipment it is the ultimate valorization of thin film research. The PLD R&D platform is the missing link between lab and fab. The first SolMateS? PLD production platform is installed in the field in 2013. This tool is the ultimate proof that PLD has now reached the maturi

L.14.4
14:15
Authors : Gulnur Aygun, Hurriyet Yuce, Lutfi Ozyuzer, Mehtap Ozdemir
Affiliations : Gulnur Aygun, Hurriyet Yuce, Lutfi Ozyuzer: Department of Physics, İzmir Institute of Technology, Urla, 35430, İzmir, TURKEY Mehtap Ozdemir: Department of Electrical and Electronics Engineering, Gediz University, Seyrek, 35650, İzmir, TURKEY

Resume : Vanadium dioxide (VO2) which is a transition metal compound demonstrates metal insulator transition (MIT) property. The transition carries out at nearly 68 ?C [1]. VO2 exhibits insulator phase with monoclinic crystal structure at low temperatures below the transition, while metallic phase with tetragonal crystal structure at high temperatures above the transition [2]. Electrical resistivity of VO2 at MIT changes by a factor of 104. VO2 has high potential for the applications in microelectronic devices. It is used not only for FET applications, but also for other devices including nonvolatile resistive memories, optical sensors and termochromic smart windows [3,4]. In this work, c-cut sapphire (Al2O3) and soda lime glass (SLG) were used as substrate. 60 nm thick VO2 films were deposited in vacuum chamber by reactive magnetron sputtering technique. The substrates were rotated for the purpose of homogeneous film growth and kept at 500 ?C during deposition. The grown films were characterized using various techniques which are X-ray diffraction (XRD) for identifying atomic and molecular crystal structure, Raman microscopy for observing vibrational and rotational modes, X-ray photoelectron spectroscopy (XPS) for chemical analysis and elemental composition, and scanning electron microscopy (SEM) to determine surface topography and composition of the films. Moreover, post annealing processes at different temperatures were done to analyse the resistance of VO2 films grown with different O2/Ar gas ratios. 1. Y. Zhao et al, ?Structural, electrical and terahertz transmission properties of VO2 thin films grown on c-,r-, and m-plane sapphire substrates?, J. Appl. Phys. 111, 053533 (2012) 2. M. Hada et al, ?Characterization of structural dynamics of VO2 thin film on c-Al2O3 using in-air time resolved x-ray diffraction?, Phys. Rev. B. 82, 153401 (2010) 3. M.Tangirala et al, ?Pysical Analysis of VO2 Films Grown by Atomic Layer Deposition and RF Magnetron Sputtering?, ECS Journal of Solid State Science and Technology, 3, N89-N94 (2014) 4. D. Ruzmetov et al, ?Three-terminal field effect devices utilizing thin film vanadium oxide as the channel layer?, J. Appl. Phys. 107, 114516 (2010) * Work supported by T?BİTAK (The Scientific and Technological Research Council of Turkey) with project number 113F349.

L.14.5
14:30
Authors : E. Svoukis*1, C.N. Mihailescu1, V. H. Mai2, O. Schneegans2, C. Lioutas3 and J. Giapintzakis*1
Affiliations : 1 Nanotechnology Research Unit & Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., 1678, Lefkosia, Cyprus 2 Laboratoire de Génie Electrique de Paris, UMR 8507 of CNRS, Paris VI and Paris – Sud Universities, Supélec, 91192 Gif – sur – Yvette Cedex, France 3 Department of Physics, Aristotle University of Thessaloniki, 54124, Thessaloniki, Greece * Corresponding authors

Resume : LiCoO2 (LCO) is a layered compound that has widely been used in the past as a cathode material in lithium-ion rechargeable batteries. Its interesting properties are attributed to redox reactions involving the cobalt-oxygen layers, linked to intercalation and deintercalation of Li ions. In this study, LCO was investigated for data storage applications based on scanning probe mediated approaches. LCO, compared to other materials proposed for scanning probe mediated nanoscale patterning, is highly stable and exhibits reversible electrochemical surface modifications. The integration of LCO in data storage applications requires the growth of high quality epitaxial thin films on substrates relevant to microelectronics industry. To this end, LCO thin films have been grown by pulsed laser deposition (PLD) on n++ Si (111) and Al2O3 (0001) substrates over a range of deposition temperatures. The crystal structure and the microstructure of the films have been investigated by using in-plane and out-of-plane high resolution X-ray diffraction and high-resolution transmission electron microscopy, respectively. The surface electrical properties of the films have been investigated via conducting probe atomic force microscopy. In this talk, the influence of the film deposition temperature on the surface electrical properties of the LCO films will be discussed along with the relevant mechanism of surface resistance modification.

L.14.2
14:45
Authors : Pini Shekhter, Cecile Saguy Uzan, J?rgen Schubert, Yaron Amouyal and Moshe Eizenberg
Affiliations : Department of Materials Science and Engineering, Technion, Haifa, Israel; Solid state institute, Technion, Haifa, Israel; Center of Nanoelectronic Systems for Information Technology, Forschungszentrum Julich, Germany; Department of Materials Science and Engineering, Technion, Haifa, Israel; Department of Materials Science and Engineering, Technion, Haifa, Israel

Resume : One of the commonly observed and reported phenomena in heterogeneous interfaces of perovskite oxides is the presence of a two dimensional electron gas (2DEG). In this study, the imperfect interface that is formed between LaLuO3 (LLO) and SrTiO3 (STO) was studied. Using XRD pole figures analysis it has been found to that LLO is deposited by pulsed laser deposition (PLD) on STO in a two perpendicular domain structure due to the large mismatch between the pseudo-cubic lattice of LLO and the cubic lattice of STO. Nevertheless, LLO presents alternately charged layers parallel to the surface and the interface between the two oxides seemed to be abrupt and smooth. Density functional theory (DFT) simulations revealed that even though the lattices of the two materials do not match, an increase of the total potential is found at the interface between the two lattices. Due to this increased potential, electrons are drawn to the interface. By utilizing localized I-V measurements in a scanning tunneling microscope (STM) cross section, indications of metallic behavior was found at the interface of this hetrostructure. Since the interface is not perfectly epitaxial, 2DEG is not formed and instead semi-continuous 0D metallic spots are spread along the interface on the LLO side. This study sheds light on the way the high concentration of charge carriers at oxide hetrostructure interfaces behaves in an imperfect interface and suggests that it is still present, only not as a 2DEG.

L.14.3
15:00
Authors : Thomas Lippert
Affiliations : Materials Group, General Energy Research Department, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland

Resume : In pulsed laser deposition (PLD) it is often just assumed that thin films will have the same composition (mainly the cations) as the target. However, the widespread use of a background gas, either inert or oxidizing, has important effects in the final film composition as well as on its thickness. We investigate the influence of the background pressure on the deposition of thin film from different multi-element targets. These targets have been specifically selected based on their elemental mass ratios. A quantitative analysis of the thin film composition as well as a semi-quantitative analysis of the plasma plume composition, at different angles and for different pressure regimes is performed. In some targets 18O isotope is used as a tracer to enable an analysis of oxygen, i.e. the origin in the thin films as well as the importance of reactions in the plasma plume and with the background gas. The first results show the influence of the pressure on the film thickness, composition and angular distribution, and how these variations depend on the specific mass ratios of the target material. A homogeneous thickness is challenging at low pressures, while at 1x10-1 mbar a uniform thickness is possible. Depositing films at an intermediate pressure may not work and can result in compositional variations of up to 15%. Analyses using 18O show that the oxygen background pressure is the most important source of oxygen for the as-grown thin films at pressure > 1x10-2 mbar.

L.14.1
15:30 Coffee break    
16:00 Round Table: Fabio Miletto-Granozio    
17:30 End of symposium    

Symposium organizers
Florencio SÁNCHEZInstitut de Ciencia de Materials de Barcelona (ICMAB-CSIC)

Campus de la UAB Bellaterra E-08193 Spain

(+34) 935801853
fsanchez@icmab.es
Gertjan KOSTERMESA+ Institute for Nanotechnology

POBox 217 Twente The Netherlands

+31 534894710
g.koster@utwente.nl
Yunzhong CHENTechnical University of Denmark

Frederiksborgvej 399 Roskilde Denmark

+45 46775614
yunc@dtu.dk
Valentin CRACIUNNational Institute for Lasers, Plasma and Radiation Physics

Atomistilor 409 P.O. Box MG-36 RO-077125 Magurele, Ilfov Romania

+40 21 457 4563
valentin.craciun@inflpr.ro