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.
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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Authors : S. Hoffmann-Eifert , F. Gunkel , R. De Souza , R. Dittmann , and R. Waser [1,2]
Affiliations :  Peter Gruenberg Institut, Forschungszentrum Juelich GmbH, and JARA-FIT, Germany;  Institut fuer Werkstoffe der Elektrotechnik II, RWTH Aachen University and JARA-FIT, Germany;  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  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 . 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  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 .  D. M. Smyth, The defect chemistry of metal oxides, Oxford University Press Inc., USA (2000)  R. De Souza, et al., Phys. Rev. B 89, 241401 (2014)  F. Gunkel, et al., Appl. Phys. Lett. 97, 012103 (2010)  F. Gunkel, et al., Appl. Phys. Lett. 100, 052103 (2012)  F. Gunkel, et al., Nanoscale 7, 1013 (2015)  F. Gunkel, et al., Symposium O, O5.3, EMRS Spring Meeting, Lille 2015.
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.
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 . Here, one key device is the magneto tunneling junction (MTJ) where two magnetic electrodes are separated by a tunneling barrier . 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 . 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 .  S.A. Wolf et al., Science 294 (2001) 1488.  S. Yuasa et al., Nature Mater. 3 (2004) 868.  T. Schemme et al., Mat. Res. Express 2 (2015) 016101.  L. Marnitz et al., AIP Adv. 5 (2015) 047103.
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.
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).
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 . 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 . The experimental data show that positive and negative anisotropic magnetoresistance can be obtained by playing with the field-driven magnetization and electrical current direction.  J. Appl. Phys. 110, 013919 (2011); New J. Physics 12, 103033 (2010); Rev. Sci. Instrum. 85, 053904 (2014)  J. Phys. D: Appl. Phys. 46 202001 (2013); J. Appl. Phys. 112, 013906 (2012);  In prep. (2015).
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.
Ferroelectric thin films I : Josep Fontcuberta
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).
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 . 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).
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:  Roelofs, A.; Schneller, T.; Szot, K.; et al. Nanotechnology, 2003, 14, 250.  Trolier-McKinstry, S.; Muralt, P. J. Electroceram., 2004, 12, 7.  Scott, J. F. Jpn. J. Appl. Phys., 1999, 38, 2272.
Authors : Patrik čajev1, 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. Gotauto 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.
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
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.
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.
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 . 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 ). 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 . 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 . 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. 041301041310. . Wisz G., Virt I., Kuzma M. Thin Solid Films (1998), v. 336, p. 188190. . 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. 3437.
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  and promising memory media which allow a simultaneous reading and writing a data . The physical properties, especially magnetism in GFO, depend strongly on the method of preparation. It forms a collinear antiferromagnetic ordering along  direction . Any disorder of the cation origin leads to non-collinear structures, such as ferromagnetic , canted antiferromagnetic  or ferromagnetic . 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.  R. Saha et al., Solid State Commun. 152 (2012) 1964  D. Stoeffler, J. Phys.: Condens. Matter 24 (2012) 185502  M.J. Han et al., Phys. Rev. B 75 (2007) 060404  J.P. Remeika, J. Appl. Phys. Suppl. 31 (1960) 263S  G.T. Rado, Phys. Rev. Lett. 13 (1964) 335  R.B. Frankel et al., Phys. Rev. Lett. 15 (1965) 958
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.
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.
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), ultravioletvisible 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.
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.
Authors : M. Scigaj , J. Gázquez , M. Varela [2,3], J. Fontcuberta , G. Herranz , F. Sánchez 
Affiliations :  Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain;  Materials Science and Technology Division, Oak Ridge National Laboratory, USA;  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.
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 UVVis. and temperature dependent dc conductivity measurements with increasing Zn-doping.
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 ZnSZnO:[Ag, Ga] thin films. ZnSZnO:[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 ZnSZnO:[Ag, Ga] samples as well as reference undoped ZnSZnO 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 ZnSZnO:[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.
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  can be used. . A. Przezdziecka, at al., Sensors and Actuators A195 ( 2013) 27 ? 31. . R. Pietruszka, at al., Mat.Sci.Semic. Proc.,25 (2014) 190-196. . L. Sosnowski, B. Orlowski, phys.stat.sol. (a) 3, 117 (1970) Supported by PNCRD (NCBiR) Project DZP/PBSII/1699/2013.
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Integration of functional oxides with silicon : Wilfrid Prellier
Authors : Matja Spreitzer1, Dejan Klement1, Zoran Jovanović1,2, Danilo Suvorov1
Affiliations : 1 Advanced Materials Department, Joef 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║Si 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.
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 . 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 . 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 . 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.  S.B. Lang, Phys. Today 58, 31 (2005)  G. Sebald et al., Smart Mater. Struct. 18, 125006 (2009)  R. Moalla et al., submitted
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: email@example.com 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.
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 . 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 . 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 . References  A. Carretero-Genevrier et al. Chem.Soc.Rev. 43, 2042 (2014)  A. Carretero-Genevrier et al. Science 340, 827 (2013)  A. Carretero-Genevrier et al. Chem. Mater. 26, 1019 (2014)
Oxide thin film growth I : Yunzhong Chen
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.
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.
Ferroelectric thin films II : Jacobo Santamaria
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.?
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, Joef 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).
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 , as a dielectric covering layer for carbon nanotubes or graphene layers , 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 . 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.  B. Hoex et al, Applied Physics Letters 91, 112107 (2007)  Steven M. George, Chem. Rev. 2010 (110) 111  E. Palomares et al. J. Am. Chem. Soc. 2003 (125) 475  M. Law et al J. Phys. Chem. B 2006 (110) 22652  Polman A., J. Appl. Phys. 82 (1) 1
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.
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.
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.
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.
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 TecnologiaIIT, 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  and the one predicted by polar catastrophe model  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 , corresponding to the strongly depleted charge density regime, thermopower displays high negative values of the order of 10^410^5 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.  S. Thiel et al, Science 313, 1942 (2006).  A. Ohtomo and H. Y. Hwang, Nature 427, 423 (2004).  I. Pallecchi et al, Nat. Commun. 6, 6678 (2015).
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.
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.
Authors : Sergejus Balčiūnas, Maksim Ivanov, Jūras Banys, Valentina Plauinaitienė, 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.
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.
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. . 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.  P. Christian, F. Von der Kammer, M. Baalousha, Th. Hofmann; Ecotoxicology 17 (2008) 326
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.
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 . 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.  B. Kalska-Szostko, E. Brancewicz, P. Mazalski, J. Szeklo, W. Olszewski, K. Szymański, A. Sidor, Acta Physica Polonica A 119 (2009) 542-544
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.
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.
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.
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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.
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.
Advanced characterization of oxide thin films and interfaces : Fabio Miletto-Granozio (Room 328, MINI building)
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.
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Oxide thin film growth : Valentin Craciun
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
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.
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