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2015 Fall

Characterization of materials by experiments and computing

V

Stress, structure, and stoichiometry effects on the properties of nanomaterials

Nanomaterials and nanostructures are playing an increasing role in everyday life as part of complex (miniaturized) electronic devices but also as components of modern tools for diagnosis and treatment in medicine. Because of that, preparation and characterization of well controlled, at the nanoscale size, of complex nanomaterials and nanostructures is of paramount importance for their applications. The proposed symposium provides an interdisciplinary forum to discuss recent progress in the area of production, characterization and principal applications of nanomaterials and nanostructures.

 

Scope

 

It is proposed a symposium that will be the follow-up of the two symposia “Stress, structure and stoichiometry, effects on the properties of nanomaterials”, held at the E-MRS Fall Meetings of 2011 and 2013 with very good attendance. Nanomaterials play now a crucial role in most aspects of advanced technologies, because of their surprising variety of functional properties. These properties can be finely tuned with a vast multitude of physical and chemical synthesis techniques. In particular, structure and stoichiometry are the key ingredients in this tuning at the nanometer scale. Stress, chemical phase and presence of defects and dislocations are critical factors governing the (nano)fabrication procedures; the investigation of their influence on the electric, magnetic optical and mechanical properties of the ever growing collection of nanosystems is a crucial challenge in material science, and it is also necessary for the engineering of the new devices to be realized for future applications. The scope of the symposium is to provide a forum for presentation and discussion of innovative methods in fabrication, characterization and modelling of nanomaterials and nanostructures: ultrathin films, nanotubes, nanopillars, nanowires, nanoparticles, with emphasis on influence of stress and stoichiometry on their properties.

 

Hot topics to be covered by the symposium

 

  • Influence of the deposition process on the structure of nanomaterials
  • Heterostructures and superlattices
  • Investigations and engineering of interfaces in nanomaterials for enhanced properties 
  • Advances in small scale characterization techniques
  • Use of self-organization and templates to grow nanostructures
  • Strain control and its effects on functional properties
  • Atomistic models for stress and defects in nanostructures
  • Interface effects in magnetic, optical and electric properties of nanosystems
  • Measuring and modeling friction at moving interfaces

 

 

Tentative list of invited speakers

 

  • Chantal Leborgne: GREMI , Orleans, France
  • Paolo Ossi, Politechnico di Milano, Italy, From isolated particles to nanoparticle arrays: laser tailored film nanostructures to identify molecules at diluted concentrations
  • Valentin Craciun, INFLPR, Bucharest, Romania
  • Florencio Sanchez, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain 
  •  Dhananjay Kumar, North Carolina A & t State University, USA
  • Fabien Paumier, Institut Pprime – CNRS, University of Poitiers, France
  • Chi Lun Pang Chemistry Dept. University College London, UK
  • Giordano, Dipartimento Scienza dei Materiali, Università di Milano Bicocca (computational, ultrathin oxide films)

 

Tentative list of scientific committee members

 

J. Moser (Spain), E. Garnet (Denmark), F. Ruffino (Italy), S. Cabrini (USA), D. Drouin (Canada), M. Schnabel (Germany), G. Leonhard (Austria), I. Boarino (Italy), M. Laus (Italy), G. Fleury (France), Paola Luches (Italy), Dimitis Niarchos (Greece), Socrates Pantelides (USA), Raluca Muller (Romania)

 

The symposium will be co-organized by the EU 7-th Framework Programme under the project REGPOT-CT-2013-316014(EAgLE). 

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V and W Symposia Joint Session 1 : chair Ewa Jedryka
09:10
Authors : Alberta Bonanni
Affiliations : JKU Institute of Semiconductor and Solid State Physics

Resume : We summarize our recent work on the fabrication of III-nitrides doped with transition metals, with particular focus on the self-aggregation driven by fabrication parameters and co-doping [1] of functional magnetic nanocrystals [2-5], layered heterostructures [6,7] and magnetooptically active complexes [8,9]. An overview will be given on how we have unraveled and we can now control the correlation between the growth parameters and structural architecture, self-assembling of embedded crystalline nanostructures and phase separation that determine the magnetic, electric and optical response of the modulated systems. The work was supported by the European Research Council (ERC, Project #227690), by the Austrian Science Fundation (FWF, Projects #20065, #22477, #24471), by WRC ETI+ (Project NanoMat, P2IG.01.01.02-02-002/08 and the European Operational Programme Innovative Economy) and by the CAPACITIES project REGPOT-CT-2013-316014 (EAgLE). [1] A. Bonanni and T. Dietl, Chem. Soc. Rev. 39, 528 (2010). [2] A. Bonanni et al., Phys. Rev. Lett. 101, 135502 (2008). [3] A. Navarro-Quezada et al., Phys. Rev. B 81, 205206 (2010). [4] A. Navarro-Quezada et al., Phys. Rev. B 84, 155321 (2011). [5] A. Grois et al., Nanotechnology 25, 395704 (2014). [6] T. Devillers et al., Cryst. Growth Des. 15, 587 (2015). [7] M. Rovezzi et al., arXiv1412.3932 [8] T. Devillers et al., Scientific Reports 2, 722 (2012). [9] T. Devillers et al., Appl. Phys. Lett. 103, 211909 (2013).

V.1.1
10:00
Authors : Matthieu JAMET
Affiliations : Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France. CEA, INAC-SP2M, F-38054 Grenoble, France.

Resume : The field of ferromagnetic semiconductors evolves very fast nowadays for their potential use in spintronic devices. Up to now, efforts have mainly focused on Diluted Magnetic Semiconductors but Curie temperatures in these materials still remain modest. One possible route to increase at least locally transition temperatures is to use spinodal nanodecomposition leading to the formation of transition metal-rich high-TC nanostructures [1]. We focus here on (Ge,Mn) considered as a model system for spinodal decomposition and compatible with Si-based microelectronics. (Ge,Mn) films grown on Ge substrates by molecular beam epitaxy at low temperature (<180°C) are free from secondary phase and contain self-assembled Mn-rich nanocolumns exhibiting high-TC [2]. In this talk, I will present a complete phase diagram of nanocolumns as a function of the substrate (Ge, GaAs) and growth temperature, Mn concentration and Sn co-doping focusing on their size, density, composition, morphology, crystalline structure and magnetic properties. For this purpose, we have used highly sensitive techniques at large scale facilities like synchrotron radiation based x-ray diffusion, diffraction and absorption, atom probe tomography, low energy muons spectroscopy and small angle neutron scattering. Only these techniques allowed us to probe in detail the physical properties at the nanoscale in the spinodally decomposed (Ge,Mn) system. [1] T. Dietl, K. Sato, T. Kukushima, A. Bonanni, M. Jamet, A. Barski, S. Kuroda, M. Tanaka, P. N. Hai, H. Katayama-Yoshida, arXiv: 1412.8062, accepted in Rev. Mod. Phys. (2015) [2] M. Jamet, A. Barski, T. Devillers, V. Poydenot, R. Dujardin, P. Bayle-Guillemaud, J. Rothman, E. Bellet-Amalric, A. Marty, J. Cibert, R. Mattana, S. Tatarenko, Nat. Mater. 5, 653 (2006).

V.1.3
 
V and W Symposia Joint Session 2 : chair Alberta Bonanni
11:00
Authors : L. Michez 1, F. D?Acapito 2, E. Prestat 3, M. Jamet 3, F. Boscherini 4, M. Petit 1, V. Le Thanh 1
Affiliations : 1 Aix-Marseille Universit? - CNRS CINaM-UMR, 13288 Marseille, France 2 ESRF, 38043 Grenoble, France 3 INAC/SP2M, CEA-Grenoble, Grenoble, France 4 University of Bologna, 40127 Bologna, Italy

Resume : Much attention has been recently devoted to Mn5Ge3 as this compound meets all the requirements for spin-polarized transport and injection into Ge. This material may therefore represent a new route to develop the beyond complementary metal-oxide-semiconductor technology. Its limited Curie temperature (TC~296K) greatly hinders its use for potential applications but can be enhanced up to 450K by incorporating a small amount of carbon. Theoretical calculations attribute this behavior to an enhancement of the Mn-Mn interactions mediated by C atoms placed in interstitial sites. In this work, we have extensively studied the structural and magnetic properties of Mn5Ge3Cx films grown on Ge(111) by molecular beam epitaxy as a function of C concentration. Besides the compressive strain induced by the incorporation of C, the latter modifies significantly the Mn5Ge3 magnetic properties. Whereas Tc increases from 296K to 450K, the magnetocrystalline anisotropy in C-doped samples is reduced by nearly a factor 10 as x is increased from 0 to 0.7. This effect is assigned to hybridization between Mn and C atoms whose position has been investigated via EXAFS and STEM experiments. The magnetic properties of carbon-doped Mn5Ge3Cx thin films can therefore be tuned by adjusting the amount of C. This is very promising for the realization of spintronics devices and in addition, the presence of C is essential for the thermal stability and the high performances of Mn5Ge3 thin films.

V.2.1
12:10
Authors : Irene Villa†, Anna Vedda†, Markus Niederberger‡, Alessandro Lauria‡*
Affiliations : †: Department of Materials Science, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milano, Italy. ‡: Laboratory for Multifunctional Materials, Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland.

Resume : In this work we report the tunable optical features observed in undoped monoclinic HfO2 nanocrystals and their dependence on the structural properties of the material at the nanoscale. Transmission electron microscopy together with X-ray diffraction and surface area measurements were used to determine the fine structural modifications, in terms of crystal growth and coalescence of crystalline domains, occurring during a calcination process in the temperature range from 400 to 1000 °C. The fit of the broad optical emission into spectral components, together with time resolved photoluminescence, allowed us to identify the dual nature of the emission at 2.5 eV, where an ultrafast defect-related intrinsic luminescence (with decay time of few ns) overlaps with a slower emission (decay of several s) due to extrinsic Ti - impurity centres. Moreover, the evolution of intrinsic visible bands during the material transformation was monitored. The relationship between structural parameters uniquely occurring in nanosized materials and the optical properties was investigated and tentatively modelled. The blue emissions at 2.5 and 2.9 eV are clearly related to defects lying at grain boundaries, while an unprecedented emission at 2.1 eV enables, at relatively low calcination temperatures, the white luminescence of HfO2 under near-UV excitation.

V.2.4
15:00
Authors : D. A. Pawlak, M. Gajc, K. Sadecka, P. Osewski, K. Korzeb, S. Turczynski, K. Wysmułek, J. Sar
Affiliations : Institute of Electronic Materials Technology, Warsaw, Poland Centre of New Technologies, Warsaw University, Poland

Resume : Recent recognition that some materials (e.g. certain metals) have negative dielectric permittivities at frequencies below their plasma frequency, and therefore provide possibilities of fabricating hybrid materials of high impact for photonic applications, has caused rapid development of two new research areas: plasmonics and metamaterials. However, the fabrication of nanosized metallodielectric structures remains a challenge. Most current fabrication techniques arrange metal nanoelements on dielectric surfaces. The methods used are either time-consuming and costly (e.g. lithography), or restricted to the creation of two-dimensional structures at a limited production scale. One of the future ways of obtaining metamaterials or materials with unusual electromagnetic properties are the bottom-up manufacturing methods, which may enable manufacturing of two-dimensional and three-dimensional structures. Theoretical proposals for and experimental demonstrations of bottom-up approaches are scarce and exhibit drawbacks. Recently, we proposed the idea of utilizing directional solidification as a method for manufacturing metamaterials and plasmonic materials. We develop two methods: (i) method based on directionally-grown self-organized eutectic structures; and (ii) NanoParticles Direct Doping method (NPDD) based on directional solidification of dielectric matrices doped with various nanoparticles. In both of these methods we can easily use all available resonant phenomena to develop materials with unusual electromagnetic properties. Eutectics are simultaneously monolithic and multiphase materials forming self-organized micro/nanostructures, which enable: (i) the use of various component materials including oxides, semiconductors, metals, (ii) the generation of a gallery of geometrical motifs and (iii) control of the size of the structuring, often from the micro- to nanoregimes. On the other hand, the novel method of NanoParticles Direct Doping enables doping of dielectric matrices with various nanoparticles (varying chemical composition, size and shape) and with the possibility of co-doping with other chemical agents as eg. optically active rare earth ions or quantum dots. In both cases we apply one of the crystal growth methods - the micro-pulling down method - to create the material. This method has been originally developed for manufacturing of single crystalline fibres and than used for directional solidification of eutectics and finally for directional solidification of glasses. Utilizing described above methods we demonstrated (i) volumetric eutectic-based material with localized surface plasmon resonance at visible wavelengths; (ii) enhanced luminescence and up-conversion processes in the eutectic material exhibiting LSPR and co-doped with erbium ions; (iii) volumetric matrix-nanoparticles-based materials with plasmonic resonances at visible and IR wavelengths based on silver (Ag), antimony-tin-oxide (ATO) and titanium nitride nanoparticles (TiN); (iv) matrix-nanoparticles-based composite with enhanced photoluminescence at the telecommunication frequency of 1.5 µm; (v) material with subwavelength transmission at IR frequencies; (vi) material with anomalous refraction, evaluated by the beam deviation measurements; (vii) materials with enhanced Faraday effect; and (viii) materials for phonoanodes in photoelectrochemiacal cells for generation of hydrogen. All these results will be described. Our new approach based on utilizing the standard crystal growth methods combined with the bottom-up approach for manufacturing metamaterials and plasmonic materials leads to novel manufacturing solutions for applications in areas such as photonics, optoelectronics, photovoltaics and photoelectrochemistry.

V.3.4
 
V and W Symposia Joint Session 4 : chair Chris Palmstrom
16:00
Authors : Paolo M. Ossi
Affiliations : Dipartimento di Energia, Politecnico di Milano, via Ponzio 34-3, 20133 Milano

Resume : By nanosecond pulsed laser ablation in ambient gas nanoparticles (NPs) form and grow in the propagating laser-generated plasma plume. Such NPs mutually self-assemble on a substrate producing elaborated architectures with controllable morphology and increasing thickness. Besides laser wavelength, target to substrate distance, gas nature and pressure, at fixed laser energy density the energy per pulse and the spot size strongly affect the amount of ablated matter and thus plume energetics. At landing on the substrate NP size, energy and mobility affect film growth, morphology and physico-chemical properties. Ag and Au targets were ablated in Ar (10-100 Pa), changing the pulse number (500-30000), keeping constant target to substrate distance, incidence angle, laser wavelength and energy density. Films consisting of NP arrays were deposited on various substrates. The morphology ranged from isolated NPs to island structures, as observed by SEM and TEM. From fast imaging of the plume the plasma propagation regime and its initial velocity were determined. This data and the measured average ablated mass per pulse allow to model in-plume NP growth. Controlling growth parameters NP aggregation is finely tuned to obtain high-performance Surface Enhanced Raman Scattering (SERS) substrates. Good sensitivity and reproducibility of the SERS signal was proved for the anti-Parkinsonian drug apomorphine, in aqueous and in biological solutions and for the anti-epileptic drug carbamazepine.

V.2.9
16:30
Authors : P. Camarda, L. Vaccaro, F. Messina, M. Cannas
Affiliations : Department of Physics and Chemistry, University of Palermo, Italy

Resume : Pulsed laser ablation in liquid phase (PLAL) is a versatile method to synthesize high-purity nanomaterials such as ZnO nanoparticles (NPs), currently the subject of a large scientific interest stimulated by their promising technological applications. They are characterized by two emission bands both excited above the energy gap (3.4 eV): 1) exciton related at 3.3 eV; 2) defect related at 2.3 eV, commonly attributed to oxygen vacancies. Existing studies have used only ex-situ methods to characterize the endproducts of PLAL; these approaches only provide indirect information on the sequence of reactions ultimately yielding stable metal oxide NPs. In this work, we report online absorption (OA) and photoluminescence (PL) measurements carried out during and after PLAL of a Zn plate in H2O. Our experimental setup is original in that it uses the kinetics of OA and PL signals to follow in real time the dynamics leading to the formation of ZnO. We demonstrate that initially-produced Zn NPs are not "instantaneously" oxidized within the plasma plume, but rather as consequence of their reactions with H2O. In fact, ZnO NPs are formed by a sequence of two steps: an early, defect-free superficial oxidation of Zn NPs, followed by a second slower oxidation of the Zn core, finally producing sub-stoichiometric ZnO NPs rich of oxygen vacancies. This information can be used to control the defect concentration allowing the tuning of PL band of the ZnO NPs.

V.2.10
16:45
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 : Nowadays, nanotechnology is a broad field of action of both science and everyday life. Continuously new materials are discovered with amazing physical and chemical properties. In case of nanoparticles, especially magnetic one are of special interest last time. It was find out that the properties strongly depend on the composition of core but also on the type of surface layer. For example, doping of iron oxide nanoparticles with different 3d metals, changes their magnetic properties significantly. When iron oxide nanoparticles are doped with Mn, Ni, or Co it enhances ferromagnetic properties usually observed. On the other hand when non-magnetic metals are used (Zn, Al) nanoparticles exhibit rather superparamagnetic behaviour at RT [1]. In this presentation we would like to show, how magnetite nanoparticles properties changes, while inorganic core is modified with different metals. Presented analysis of these structures include TEM, EDX, X-ray diffraction, and Mössbauer spectroscopy studies. [1] B. Kalska-Szostko, U. Wykowska, D. Satuła, Applied Surface Science 360 (2014) 7-15

V.2.11
17:30
Authors : L. Grządziel, M. Krzywiecki
Affiliations : Institute of Physics–CSE, Silesian University of Technology, Konarskiego 22B, 44-100 Gliwice, Poland

Resume : Perspective material for organic nanoelectronics development is group of metallophthalocyanine (MePc) thin films already applied in e.g. organic light emitting diodes, organic thin film field effect transistors, solar cells and gas sensors. Application of organic nanolayer is strongly dependent on the electronic and chemical properties of its surface. Operating in real-world conditions, these properties are modified due to contact with air. This interaction leads to adsorption of ambient atoms or molecules on MePc surface inducing charge transfer between them. Process affects organic chemical bonds manifesting change of surface chemical structure. It may provoke variation of electronic surface states occupation and modify electronic parameters. In work, the copper phthalocyanine (CuPc) thin films (16, 32, 500 nm thick) were deposited on different Si(111) substrates. Surface electronic parameters and chemical structure were investigated by ultraviolet and angle resolved X-ray photoelectron spectroscopies as well as by photoemission yield spectroscopy before and after air exposure, depending on substrate type. Collected electronic parameters changes were correlated with morphological features measured by atomic force microscopy. Studies indicated particular electronic tendency for oxidation processes for certain shapes of CuPc crystallites. Contaminating chemical species were recognized and underwent depth distribution analysis.

V.V I.2
17:30
Authors : R. А. Shkarban, Т. S. Dosenko, S. I. Sidorenko, Iu. N. Makogon
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine

Resume : Improving the efficiency of thermoelectric materials is possible through a use of nanoscaled materials, such as nanofilms. A promising material for research is considered to be the antimonide CoSb3 (skutterudite). Functioning of thermoelectric devices largely depends on stability of phase composition, microstructure and properties of thin films deposited on suitable substrates. In this paper, it is stated a relation between the phase composition, structure of the nanoscaled films based CoSb3 and residual stresses. The investigated 30-nm-thick CoSbх(3.6 ≤ х ≤ 4.2) films with the excess of antimony were prepared by molecular beam deposition in vacuum on a SiO2(100 nm)/Si(001) substrate at the temperature of 200oC, followed by annealing in vacuum in the range of 300оС - 700оС. In the deposited films the polycrystalline untextured CoSb3 and Sb phases were observed. Thermal stability of crystalline CoSb3.6 (30 nm) and CoSb4.2 (30 nm) films keeps up to  300°C. At annealing of nanoscaled CoSbx(30 nm) (3.6 ≤ x ≤ 4.2) films at temperatures above 300°C - 400°C sublimation of not only excessive Sb but also of Sb from antimonide CoSb3 occurs. At annealing of the films, antimony first diffuses to the grain boundaries from where it then sublimates. The level of stress varies. After deposition in the films it is observed a slight level of tensile stress 1 GPa, which raises after thermal annealing up to  5 GPa and is accompanied by appearing of pores and cracks in the film.

V.V I.4
17:30
Authors : O. V. Fihurna, I.O. Kruglov, K.V. Slipchenko, S.I. Sidorenko, Iu.N.Makogon
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine

Resume : Effect of Ag(7,5mn) layer location (as top, underlayer and intermediate layer) on the phase and structural transformation in Fe50Pt50 thin films on SiO2(100 nm)/Si(001) substrates were investigated by methods of XRD, AFM. Magnetic properties were measured by SQUID. All as-deposited samples show disordered A1(FePt) structure. The location of additional Ag layer affects the initial stress/strain state in FePt layer, and thus the temperature of A1 in L10 phase transformation. In comparison with Ag top and underlayer films the films with intermediate Ag layer have a more high level of compressive stresses that lead to a decrease of ordering temperature of the L10 phase formation by 100°С up to 700°C. In the film with Ag top and underlayer L10 phase was formed after annealing at more high temperature above 800°С. Ag diffuses along boundary grains and decreases exchanging coupling interaction between FePt grains that lead to increasing of coercivity to big values of 20 kOe in films with Ag underlayer. The authors would like to thank Prof. M. Albrecht and Dr. G. Beddies and workers from Chemnitz University of Technology (Germany) for sample preparation, assistance in conduction of investigations and discussion of results.

V.V I.5
17:30
Authors : T.I. Verbytska, M. Yu. Verbytska, A. I. Falovska, S.I. Sidorenko, Iu.N.Makogon
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine

Resume : Influence of Au intermediate layer in nanoscaled Fe50Pt50(15nm)/Au(x nm)/Fe50Pt50(15nm) film composition (where х = 0;7.5;15;20; 30 nm) on SiO2(100 nm)/Si(001) substrates on the transformation of disordered А1(FePt) phase into ordered L10 (FePt) phase at annealing in vacuum was investigated by methods of XRD; AFM and MFM. Magnetic properties were measured by SQUID and magneto-optic Kerra effect method. It was established that during deposition the А1(FePt) phase forms in all films. Au interlayer thickness effects on initial stress/strain state in FePt layer and thus on temperature of А1 L10 phase transformation. As-deposited films with Au of 7.5 and 30 nm have a high level of compressive stresses in comparison with film without Au layer that lead to decreasing of ordering temperature of L10 phase. The formation of L10 phase in film with 7.5 nm-thick Au occurs during annealing at 650°С. Increase of Au thickness up to 20 and 30 nm decreases the ordering temperature up tо 600°С. Coercivity of film with 7.5 and 30 nm Au interlayers after annealing at 900°С increases up to 16.55 to 27.3 kOe, correspondingly. Au diffuses along boundary grains and decreases exchanging coupling interaction between FePt grains that lead to increasing of coercivity. The authors would like to thank Prof. M. Albrecht and Dr. G. Beddies and workers from Chemnitz University of Technology (Germany) for sample preparation, assistance in conduction of investigations and discussion of results.

V.V I.6
17:30
Authors : Katarzyna Grochowska1, Katarzyna Siuzdak1, Jakub Karczewski2, Mariusz Szkoda3, Gerard Śliwiński1
Affiliations : 1Centre for Plasma and Laser Engineering, The Szewalski Institute, Polish Academy of Sciences, 14 Fiszera St., 80-231 Gdańsk, Poland; 2Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, Narutowicza 11/12 St., 80-233 Gdańsk, Poland; 3Faculty of Chemistry, Gdańsk University of Technology, Narutowicza 11/12 St., 80-233 Gdańsk, Poland

Resume : Noble metal nanostructures are the object of great interest due to their unique optical and electronic properties exploited in nanotechnology, medicine, biochemistry and surface enhanced spectroscopies. In this work the geometry and the optical and spectroscopic properties of the Au nanoparticle (NP) structures obtained by dewetting are investigated in dependence on their preparation conditions. Structures are produced from thin Au films (5-20 nm) sputtered onto the ITO, FTO and glass substrates. The dewetting is performed by thermal treatment in ambient air. SEM inspection of the structures reveal breakup of the Au films into NPs of nearly spherical shape. The NP size does not exceed 100 nm and can be tuned by changing the initial thickness of the Au layer and the substrate material, too. In the absorbance spectra the broad peaks centered around 550-610 nm are ascribed to resonant absorption of the surface plasmons and the nonradiative and radiative contributions to broadening of the absorption profile are estimated. As observed, for large particles the radiative component is dominant while the nonradiative one is small and remains approximately constant for all examined samples. The large signal values observed in Raman spectra confirm that the investigated materials can serve as active substrates for surface enhanced spectroscopy. KG and KS acknowledge the National Science Centre of Poland for financial support via grants 2012/07/N/ST5/02139 and 2012/07/D/ST5/02269.

V.V I.9
17:30
Authors : C. N. Mihailescu1, 2, R. Negrea3, C. Ghica3, C. R. Luculescu and J. Giapintzakis1*
Affiliations : 1Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Avenue,PO Box 20537, 1678 Nicosia, Cyprus 2National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125 Magurele, Romania 3National Institute of Materials Physics, RO-077125 Magurele, Romania

Resume : The further miniaturization in semiconductor technology has led to nanoscale chip feature sizes and significant increases in on-chip power dissipation as well as heat flux at the silicon level [1]. New materials and process improvements are required to minimize thermal resistance. Recently, the 1D half-spin Heisenberg antiferromagnet La5Ca9Cu24O41 has attracted considerable attention due to his highly anisotropic magnon-mediated thermal conductivity [2]. Since the heat is conducted primarily along one crystal axis, a solution to efficiently channel away parasitic heat such as that generated in integrated semiconductor circuits may come from using a heat conductive layer of such material. However, in order to exploit this anisotropic heat transport property, there are several important requirements which need to be considered: i) to obtain La5Ca9Cu24O41 in a stoichiometric thin film form and ii) the films have to be epitaxially grown. Recent literature on the growth of complex oxide thin films proposes the lattice mismatch induced strain as another way to obtain an epitaxial growth. It has also been suggested that there is a strong correlation between the interfacial strain, the lattice mismatch and the film thickness, i.e., the thinner the film the larger the interfacial strain/stress. In this work we have investigated the effect of the interfacial strain on the growth of La5Ca9Cu24O41 thin films. Films with various thicknesses have been grown on SrTiO3 substrates by Pulsed Laser Deposition (PLD). The films composition has determined by energy dispersive spectroscopy (EDX). Their crystal structure has been studied by high resolution X-ray diffraction (HR-XRD) and high resolution transmission electron microscopy (HR-TEM), while their strain nature has been evaluated from HR-XRD and Geometrical Phase Analysis (GPA) measurements. [1] C. Bachmann and A. Bar-Cohen, 11th Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, IEEE, p. 238, Orlando (2008). [2] C. Hess, C. Baumann, U. Ammerahl, B. Buchner, F. Heidrich-Meisner, W. Brenig, and A. Revcolevschi, Phys. Rev. B, 64, 184305, (2001).

V.V I.12
17:30
Authors : G. Socol1, D. Craciun1, G. Dorcioman1, N. Stefan1, V. Craciun1, D. Cristea2, L. Floroioan3, M. Badea4, D. Pantelica5, P. Ionescu5
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, Măgurele, Romania; 2Materials Science Department, Transilvania University, Brasov, Romania; 3 Fac Elect Engn & Comp Sci,Transilvania Univ Brasov, Brasov, Romania 4Faculty of Medicine, Transilvania University, Brasov, Romania; 5Horia Hulubei National Institute for Physics and Nuclear Engineering, Măgurele, Romania

Resume : Transition metal carbides and nitrides have been extensively investigated as hard and protective coatings since they possess both excellent ceramic and metallic properties. Such properties are very useful for many applications where there is a combination of mechanical wear under corrosive liquids. The Pulsed Laser Deposition (PLD) is the best technique to grow thin carbide and nitride films to investigate their properties. It has been observed that PLD grown films are under rather high compressive stress values. We deposited ZrC, ZrN, TiN and TiC thin films using the PLD technique under various conditions on Ti, Si and stainless steel substrates. The mechanical properties of the films were characterized by nanoindentation, scratch and wear tests. The structural properties were obtained from grazing incidence X-ray diffraction and X-ray reflectivity investigations. The chemical composition was measured by Rutherford backscattering spectrometry. Measurements involving corrosion and electrochemical impedance spectroscopy studies were carried out in physiological solutions to investigate the chemical stability of the PLD grown films. These investigations helped us understanding the effect of the stress on the mechanical and corrosion resistance of PLD grown films.

V.V I.13
Start atSubject View AllNum.
 
Session 5 : chair Paolo Ossi
09:00
Authors : Chantal Boulmer-Leborgne1, Thibault Labbaye1, Eva Kovacevic1, Shahzad Hussain1, Soufyane Belhenini2, Abdellah Tougui2, Aurélien Canizares3, Mohamed-Ramzi Ammar3 , Patrick Simon3, Franck Dosseul4
Affiliations : 1-GREMI Université d’Orléans-CNRS 14 rue d’Issoudun 45064 Orléans cedex2 France 2-LMR 7 Avenue Marcel Dassault 37004 TOURS 3-CEMHTI 1D avenue de la Recherche Scientifique 45071 ORLEANS cedex 2 4-STMicroelectronics 16 Rue Pierre et Marie Curie, 37100 Tours

Resume : CNTs are a type of novel material attracting great attention due to their outstanding thermal, electrical, and mechanical properties. These properties make them a promising alternative to interconnect materials for electronic packaging applications. As the performance of semiconductor products increases, the technical challenges increase in areas of power delivery, heat removal, input/output density, and thermomechanical reliability. Down-scaling the traditional interconnects does not satisfy the requirements and the development, process, and design of interconnect materials are driven into entirely new directions. In the presented study the different growth kinetics of several kinds of catalyst/substrate couple are investigated by analyzing the CNT carpets at different times during the PECVD growth, by NEXAFS ex situ and Raman in situ for different experimental conditions. Electrical, thermal and mechanical properties are determined on CNT carpets and interconnect tests are achieved for industrial applications.

V.5.1
09:30
Authors : J.M. Macak (a), P. Knotek (b), H. Sopha (a), M. Krbal (a), J. Subrt (c), M. Klementova (c)
Affiliations : (a) Center of Materials and Nanotechnologies, Faculty of Chemical Technology, University of Pardubice Nam. Cs. Legii 565, 530 02 Pardubice, Czech Republic; (b) Dep. of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice Studentska 573, 532 10 Pardubice, Czech Republic; (c) Institute of Inorganic Chemistry of AS CR, Husinec-Rez 1001, 25068 Rez, Czech Republic

Resume : Synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The nanoporous Al2O3 – most established material of this group – has been prepared by anodic oxidation of Al under suitable electrochemical conditions into perfectly ordered, honeycomb-like porous structures (Masuda & Fukuda, Science, 1995). It is the TiO2 that has received the next highest attention motivated by its range of applications. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the Ti substrate is converted into highly-ordered nanotubular layer in suitable electrolytes. Although advancements in the anodic synthesis of TiO2 nanotube layers have been presented over past years, the degree of ordering has not reached so far the level known from porous Al2O3. Numerous factors influence the ordering and the homogeneity of TiO2 nanotube layers. In the presentation, we aim to demonstrate considerably significant advancements in the ordering of anodic TiO2 nanotubes and its implications. We will show how to obtain via tailored anodization protocols a very decent degree of uniformity and homogeneity of the nanotube layers. Moreover, based on SEM, EBSD and TEM measurements, we will demonstrate how the Ti grain structure influences the lateral uniformity of the nanotube layers.

V.5.2
09:50
Authors : Kunmo Chu, Sangeui Lee, Chang seung Lee
Affiliations : Samsung Advanced Institute of Technology

Resume : Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compound; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either negative (NTC) or positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we have demonstrated a new hybrid bi-layer zero-TCR composite consisting of stacked layers showing NTC and PTC of resistance. The bi-layer composites consisted of a carbon nanotube (CNT)-based layer having a NTC of resistance and a carbon black (CB)-based layer having a PTC of resistance which was in direct contact with electrodes to stabilize the electrical resistance change during electric Joule heating. The composite showed nearly constant resistance values with less than 2 % deviation of the normalized resistance until 200 °C. The CB layer worked both as a buffer and as a distributor layer against the current flow from an applied voltage. This behavior, which was confirmed both experimentally and theoretically, has been rarely reported for polymer-based composite systems.

V.5.3
 
Session 6 : chair Sergio D'Addato
11:00
Authors : L. Spallino, L. Vaccaro, M. Cannas, F. M. Gelardi
Affiliations : Dipartimento di Fisica e Chimica, Universita degli Studi di Palermo (Italy)

Resume : The large variety of defects arising from the constraints imposed by the nanoscale is at the origin of the huge emissivity observed in SiO2 nanoparticles. Generally, broad and structureless emission bands characterize the UV-Visible spectral region, reflecting the amorphous matrix in which the defects are embedded. An exception is observed in a vacuum and consists of a structured photoluminescence, between 3.0 eV and 3.5 eV, whose sharp spectral features resemble those of a single molecule. This emission is due to the coupling of an electronic transition with two localized modes of frequency 1370 cm-1 and 360 cm-1. Its quenching in air points out that the defects are allocated on the surface of the nanoparticles and strongly interact with the molecular species of the environment. The pronounced sensitivity to the atmosphere, in combination with the advantageous spectral features, is promising for the use of SiO2 nanoparticles as luminescent sensors of small molecules. To this aim, the understanding of the fundamental mechanisms of the quenching is mandatory. By using time resolved photoluminescence technique, we have carried out a detailed investigation of the effects on the intensity and lifetime of the structured emission on varying the interaction with specific molecular species (O2, N2). The findings indicate that the quenching mechanisms is controlled by collisional- and reaction-limited processes thus evidencing the sensing property of SiO2 nanoparticles.

V.6.1
11:30
Authors : V. Braza-Blanco1, D. F. Reyes1, T. Ben1, A. D. Utrilla2, J. M. Ulloa2, D. Gonzalez1.
Affiliations : 1 Departamento de Ciencia de los Materiales e IM y QI, Universidad de Cádiz, 11510 Puerto Real (Cádiz), Spain; 2 Institute for Systems based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain

Resume : Nowadays, depositing specific capping layers (CLs) on InAs quantum dots (QDs) consisting of GaAs-based alloys is a promising way to tailor the optical properties of devices for telecommunication and solar cell applications. However, the nature and the growth conditions of such CLs are critical parameters determining the final structural and optical properties of the QDs. In this work, we analyze statistically, by transmission electron microscopy (TEM) and atomic force microscopy (AFM) techniques, the effect of a variety of GaAs(Sb)(N) CLs on QD parameters such as height, aspect ratio and volume. Firstly, AFM and TEM revealed that the buried QDs, compared to the uncapped ones and independently of the capping material, always evolve into a dome shape undergoing an asymmetric decomposition with a considerable reduction of the base diameters but not of their heights. The CL features such as composition and growth rate, affect the amount of the QD volume reduction but not the average aspect ratio, which is preserved. Remarkably, the analysis of indicative parameters such as the radius of curvature, among others, reveals that the QD erosion in GaAs-based CLs follows a unique trend independently of the different decomposition mechanisms involved, whereby the addition of Sb and/or N only strengthen or weaken this process in a relative small percentage.

V.6.2
12:10
Authors : Yang Han, Ming Hu
Affiliations : Institute of Mineral Engineering, Division of Materials Science and Engineering, Faculty of Georesources and Materials Engineering, RWTH Aachen University, 52064 Aachen, Germany; Aachen Institute for Advanced Study in Computational Engineering Science (AICES), RWTH Aachen University, 52062 Aachen, Germany

Resume : Well-ordered and freestanding bilayer silica  a new member of two-dimensional (2D) family  have great advantage in versatile modern technologies and applications that range from insulating layers in integrated circuits to supports for sensors and catalysts, as well as protective films against corrosion etc. Motivated by this, a lot of work on mechanical properties has been done, while thermal transport properties received less attention. By performing DFT calculation a new ground state of bilayer h-silica was found. Remarkably, it has negative Poisson’s ratio at small strains, while the Poisson’s ratio has negative to positive transition at some critical strain. The underlying mechanism of the negative Poisson’s ratio stems from the intrinsic rotational angle of SiO3 triangular pyramids. Moreover, we studied the thermal conductivity of O-silica, another type of silica layer, under biaxial strain using DFT based Boltzmann transport equation. An unexpected drastic decrease in lattice thermal conductivity of O-silica with tensile strain was observed, in contrast to the behavior of graphene, a representative of 2D materials. The relationship between the unusual strain dependent thermal conductivity and the silica layer structure is further studied. The current research adds scientific value to the fundamentals of 2D materials and we expect that it will arouse great interest of experimentalists to carry forward the application of silica as new electronic materials.

V.6.4
 
Session 7 : chair Chantal Leborgne
14:00
Authors : A. Higo, C. Thomas, T. Kiba, J. Takayama, C.Y. Lee, Y. Tamura, ,I. Yamashita, M. Sugiyama, Y. Nakano, A. Murayama, S. Samukawa,
Affiliations : WPI-AIMR, Tohoku Univ.; IFS, Tohoku Univ.; Hokkaido Univ.; Hokkaido Univ.; IFS, Tohoku Univ.; IFS, Tohoku Univ.; NAST; the Univ. of Tokyo; the Univ. of Tokyo; Hokkaido Univ.; IFS, Tohoku Univ.;

Resume : Top-down fabricated quantum nanodisks (QNDs) lasers are one of the most promising light sources because of their theoretically improved performances compared to quantum well and bulk lasers. The bio-template is used to create a high density etching mask and low-damage etching is performed by using neutral beam (NB). The bio-template is realized by cage-shaped proteins called ferritins of 12 nm outside diameter with a 7 nm iron oxide core, and functionalized with poly-ethylene glycol (PEG) to control the gap between cores to avoid any QNDs coupling after fabrication. After removing the protein shell by oxygen annealing, a high-density nano-pattern of cores is realized as etching mask. The NB etching system consists of an inductively coupled plasma chamber separated from the process chamber by a carbon electrode with a high aspect-ratio aperture array, therefore, the charged particles are efficiently neutralized and the UV photons from plasma almost completely screened. InGaAs/GaAs multiple quantum wells were grown by metalorganic vapor phase epitaxy (MOVPE), with a few nanometers thick InGaAs cap layer. Ferritins were self-assembled by spin-coater. After removing protein shell by oxygen annealing in vacuum, a hydrogen radical treatment was performed to remove the oxide layer. Etching was then realized by pure chlorine NB. Regrowth of GaAs barrier was done by MOVPE. Finally, InGaAs QND based light emitting diode were realized.

V.7.1
14:30
Authors : A. Carretero-Genevrier 1, Judith Or?-Sol? 2, Jaume G?zquez 2, Teresa Puig 2, Xavier Obradors2, Cl?ment Sanchez3, Etienne Ferain4, Juan Rodr?guez-Carvajal5, Narc?s Mestres2
Affiliations : 1 INL, Institut des Nanotechnologies de Lyon, France2 2 Institut de Ci?ncia de Materials de Barcelona ICMAB, Consejo Superior de Investigaciones Cient?ficas CSIC, Campus UAB 08193 Bellaterra, Catalonia, Spain 3 UPMC-Coll?ge de France-CNRS 7574. Coll?ge de France, 11 place Marcelin Berthelot, 75231 Paris 4Universit? Catholique de Louvain, Croix du Sud 1,1348 Louvain-la-Neuve, Belgium, and it4ip s.a., rue J. Bordet (Z.I. C), 7180 Seneffe, Belgium 5 Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France

Resume : Selective synthesis for integrated nanomaterials with controllable morphology and composition represents an emerging research area in nanoscience and nanotechnology because the intrinsic properties behind nanostructures are generally phase-, shape-, and size- dependent. In this direction the present work shows the capabilities of nanoporous polymeric template systems directly supported on different substrates for the confined growth of epitaxial ferromagnetic complex oxides nanostructures. In particular, we describe the versatility and potentiality of sol-gel precursor solutions combined with track-etched polymers to synthesize i) vertical polycrystalline La0.7Sr0.3MnO3 nanorods on top of single crystal perovskites [1,2], ii) single crystalline manganese based octahedral molecular sieves (OMS) nanowires on silicon substrates [3-5], and iii) the epitaxial directional growth of single crystal OMS nanowires when grown on top of fluorite-type substrates [6]. The influence of the distinct growth parameters on the nanostructural evolution of the resulting nanostructures and their magnetic properties are studied in detail. Therefore, we demonstrate that the combination of soft-chemistry and epitaxial growth opens new opportunities for the effective integration of novel technological functional complex oxides nanomaterials on different substrates. [1] A. Carretero-Genevrier et al. Chem.Soc.Rev., 43, 2042-2054 (2014) [2] A. Carretero-Genevrier et al. Adv.Funct.Mater., 20, 892-897. (2010). [3] A. Carretero-Genevrier et al. Chem.Mater., 26 (2), 1019?1028 (2014) [4] A. Carretero-Genevrier et al. JACS., 133 (11), 4053?4061 (2011) [5] J. Gazquez et al. M&M., 20 (03) 760-766 (2014) [6] A. Carretero-Genevrier et al. Chem.Comm., 48, 6223-6225 (2012)

V.7.2
16:30
Authors : Maria Chiara Spadaro1-2, Sergio D Addato1-2, Francesco Benedetti1-2, Paola Luches1, Sergio Valeri1-2, Giovanni Bertoni3, Vincenzo Grillo3, Stefano Turchini4, Anna Maria Ferretti5, Elena Capetti5, Alessandro Ponti5
Affiliations : 1 CNR-NANO, via G. Campi 213/a, 41125 Modena, Italy; 2 Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, 41125 Modena, Italy; 3CNR-IMEM, Parco Area delle Scienze 37/A - 43100 Parma, Italy; 4 Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (CNR), Via Fosso del Cavaliere 100, 00133 Roma, Italy; 5 Laboratorio di Nanotecnologie, Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Ricerche, via G. Fantoli 16/15, 20138 Milano (Italy)

Resume : A viable strategy to overcome the superparamagnetic limit in nanosized magnetic memory units is the exploitation of the exchange bias (EB) effect, [1] occurring at the interface between an Anti Ferromagnetic (AFM) and a Ferromagnetic (FM) medium. Research in this field is still in progress, trying to study and optimize every physical process affecting the EB. Recently we have studied in detail the EB in Ni@NiO core-shell nanoparticle films realized with physical synthesis methods [2], with particular interest in the effect of the AFM shell thickness. We have obtained this system in a controllable and reproducible way, in order to study separately the effect of the Ni NP size, shell thickness and core-shell interface. With this method we could demonstrate the possibility of tuning coercivity and exchange field by playing separately with the different parameters controlling the NP synthesis. Recently, we have extended our investigation on Ni@CoO NPs, by making use of SEM, XPS, HR- and S-TEM, SQUID and XMCD technique, to assess the influence of the different shell AFM anisotropy. The interplay of interface and bulk effects in EB could be explored systematically, demonstrating the viability of our method to obtain magnetic NPs with enhanced stability. Our results pave the way for a rational design and synthesis of NPs with desired magnetic properties. [1] V. Skumryev et al., Nature 423 (2003) 850; [2] S. D'Addato et al. Appl. Surf. Sci. 2014, 306, 2-6.

V.8.2
17:10
Authors : Andreas Kaidatzis, Christos Serletis, Dimitrios Niarchos
Affiliations : Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Athens, Greece

Resume : We study Ta-doped W/CoFeB/MgO stacks for Spin-Orbit Torque Magnetic Random Access Memory (SOT-MRAM) applications [1]. A typical SOT-MRAM stack is composed of a Magnetic Tunnel Junction (MTJ), two ferromagnetic layers separated by an oxide, grown on top of a high spin-orbit coupling metal. Obtaining MTJs with perpendicular magnetic anisotropy (PMA) is of crucial importance for efficiently scaling-down the memory cells to sub-22-nm technology nodes. Sputter-deposited W-Ta-alloy/CoFeB/MgO and W/CoFeB/Ta/CoFeB/MgO half-MTJ stacks are studied for determining the appropriate parameters for obtaining PMA. It has been shown in the literature that although Ta/CoFeB/MgO may readily obtain PMA after annealing [2], this is not the case for W/CoFeB/MgO stacks [3], indicating that Ta plays a crucial role as a “PMA-enhancing” element. Our main focus is on the W-Ta-alloy composition, the thickness of the Ta inter-layer and the effect that it has on the CoFeB/Ta and Ta/CoFeB interfaces, and the effect of the MgO deposition pressure on the CoFeB/MgO interface. We find that the above-mentioned parameters have to be finely tuned for obtaining PMA and maximizing the magnetic anisotropy energy. REFERENCES [1] I. M. Miron et al., Nature 476, 189 (2011) [2] S. Ikeda et al., Nature Materials 9, 721 (2010) [3] C.-F. Pai et al., Appl. Phys. Lett. 101, 122404 (2012) ACKNOWLEDGMENTS Funding from the E.C. through a FP7-ICT project (Grant No. 318144) is acknowledged.

V.8.4
17:30
Authors : Prof. Alexander Pogrebnjak; Dr. Oleksandr Bondar
Affiliations : Sumy State University (Sumy, Ukraine)

Resume : Superhard Ti-Si-N coatings were fabricated using vacuum arc evaporation of cathode. Such methods of analysis as slow positron beam (SPB), RBS, µ-PIXE (proton microbeam), XRD, SEM with EDS, XPS, nanohardness and elastic modulus measurements were applied to investigation of such coatings, before and after annealing at the temperature of 600 degrees C for 30 minutes. Redistribution of N and Si occurred on the borders of nanograins after annealing, amorphous phase α-SiNx (Si3N4) was created, defects segregated on interfaces and formed vacancy-type clusters with rather high concentration from 5х10^16 cm^(-3) to 7.5x10^17 cm^(-3) due to thermodiffusion. Solid solution (Ti,Si)N and small concentration of α-SiN (close to XRD detection limits) were formed in the coatings. Deformation reduced after thermal annealing to a value of –2.3%. Size of nanograins of (Ti,Si)N solid solution increased from 12.5 nm to (13.2÷13.4) nm, and 25 nm grains increased to 28.5 nm due to annealing under another deposition regime. Fabricated coatings were implanted by high dose Cu- ions 2x10^17 см^(-2), kinetic energy was 60 keV in order to investigate the limits of irradiation resistance.

V.V II.3
17:30
Authors : Dorota Brzuska1, Daniel Jastrzebski1, Maciej Bialoglowski1, Edyta Pesko1, Cezariusz Jastrzebski2, Slawomir Podsiadlo1
Affiliations : 1 Faculty of Chemistry, Warsaw University of Technology; 2 Faculty of Physics, Warsaw University of Technology

Resume : Among various materials being explored in search for silicon replacement in nanoelectronics, SnS2 seems to be especially valuable. Having intrinsic layered structure of crystallites and relatively high energy gap offers multiple sophisticated applications, e.g. in high on/off current field effect transistors. In this study, structural and electron properties of SnS2 nanopowders have been examined. The syntheses have been carried out in aqueous solutions, as well as in organic solvents, using metal salts, sulfur, thioacetamide etc. The obtained materials have been characterized with X-ray powder diffraction, Raman scattering spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and spectrophotometry UV/Vis/NIR.

V.V II.4
17:30
Authors : A.B. SMIRNOV, R.S. UDOVYTSKA, R.K. SAVKINA, and F.F. SIZOV
Affiliations : V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, 41, Prospect Nauky, 03028 Kyiv, Ukraine, phone: +38(044) 525 18 13

Resume : In this paper formation process of nano-heterostructures Ag2O-Hg1–xCdxTe(x=0.2) on the surface of solid solution Hg1–xCdxTe (х~0.22) has been investigated. Modification of the ternary chalcogenide semiconductor compound was performed using the method of doping the heterostructure samples with silver ions which was followed by low-temperature treatment. The energy and dose of implanted ions were 100 keV and 4.8x1013сm-2, respectively, the duration of thermal treatment was 5 hours at the temperature of 75ºС. The silver ion migration in the ion-disordered HgCdTe layer and local deformation defects are lead to the topological instability of the irradiated surfaces. The results of topometry based on AFM measurements show the network of quasi-pores with depth from 3.5 to 10 nm and diameter 50 to 160 nm, as well as grains with size 40 to 80 nm densely packed in the surface plane. After implantation with silver ions on the background of insignificant smearing of grain boundaries, with maintenance of initial surface porosity, a uniform array of cone-like spikes was formed, with height h from 5 to 25 nm and base diameter d between 13 and 35 nm. The magnitude of mechanical stresses created in the CdHgTe film after its implantation can be determined (σmax= 2.2x105 Pa). The coefficient of crystal lattice contraction by the introduced implant β was determined using the results of X-ray diffraction studies of specimens ~ 3.51x10-31m3. Deformations arising after embedding silver ions prevent the process of mercury diffusion in the implanted target. Apparently, transformation of the defect structure in semiconductor film reflects elastic relaxation “compression – extension – compression” in the region of MCT loosened by ion implantation.

V.V II.6
17:30
Authors : E. S. Bârcă1, C. Luculescu2, M. Filipescu2, V. Ion2, N.L. Dumitrescu2, M. Dinescu2, M. Abrudeanu1, C. Munteanu3
Affiliations : 1. Universitatea din Pitesti, Facultatea de Mecanica si Tehnologie, 110040, str Targul din Vale nr 1, Pitesti, Arges 2. National Institute for Lasers, Plasma and Radiation Physics, P.O. Box MG 16, RO 77125 Magurele - Bucharest, Romania 3. Universitatea Tehnica "Gheorghe Asachi" Iasi, Facultatea de Mecanica, Bld D. Mangeron nr. 61, 700050

Resume : Cerium oxide (CeO2) thin films have been deposited on Si (100) and steel substrates using pulsed laser deposition technique at different substrate temperatures from room temperature (RT) up to 500C in a controlled atmosphere of oxygen (0.1 mbar). Structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Raman, scanning electron microscopy and ellipsometry techniques. The refractive index is increasing (1.53 - 2.2) with the increasing of the substrate temperature. XRD results showed that the deposited films are polycrystalline with cubic structure. The Raman peak appeared at 460 cm−1 due to the F2g active mode. Nanostructured “pyramids” like features were observed for high temperature substrate.

V.V II.7
17:30
Authors : A.M. Titenko1, L.D. Demchenko2, S.I. Sidorenko2
Affiliations : 1 Institute of Magnetism, NAS of Ukraine, Acad. Vernadskiy avenue, 36-b, Kyiv, 03142, Ukraine, titenko@imag.kiev.ua; 2 National Technical University of Ukraine "Kyiv Polytechnic Institute", Peremogy prospect, 37, Kyiv, 03056, Ukraine, lesyademch@gmail.com

Resume : Aging Cu-Mn-Al alloys with original magnetic characteristics undergo thermo-induced martensitic transformation (MT). Nowadays, such type of MTs which occur after solid solution decomposition with ferromagnetic nanoparticles precipitation in nonferromagnetic matrix attract interest. By thermal treatment, the system of ferromagnetic nano-dispersed particles in nonferromagnetic matrix can be formed. Herewith, coherent nanoparticles precipitated during decomposition of high-temperature Cu-Al-Mn betta1-phase are coherently connected with matrix and do not undergo spontaneous MT at cooling . The influence of aging regimes of high-temperature phase on subsequent martensitic transformation in Cu-Al-Mn alloy was studied. The morphology of martensitic transformation behavior as a result of alloy aging under an annealing in a constant magnetic field with different sample orientation relatively to the field and without the field was investigated for directly control of the process of martensite induction at cooling. The temperature dependences of electrical resistance, magnetic susceptibility, and the temperature and field dependences of magnetization, phase composition were found. The tendency of oriented growth of the precipitation-phase particles in a direction of applied field and the increase of volume fraction of these particles under thermal magnetic treatment of material what favors a reversibility of induced martensitic transformation.

V.V II.8
17:30
Authors : L. Floroian, M. Badea, C. Samoila, N. Mihailescu, I. Negut, V. Craciun, I.N. MIhailescu
Affiliations : Transilvania University of Brasov, Romania National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania

Resume : We report on the transfer of novel polymer-antibiotic-bioactive glass composites by matrix assisted pulsed laser evaporation to uniform thin layers onto stainless steel implant. Influence of the deposition process on the structure of nanomaterials was studied. The targets were prepared by freezing in liquid nitrogen of mixtures containing polymer and antibiotic reinforced with bioglass powders. The cryogenic targets were submitted to multipulse ablation with an UV KrF* (λ=248 nm, τ ~ 25 ns) excimer laser source. The main advantages with this coating are multiple: stopping any leakage of metal and metal oxides to the biological fluids and finally to inner organs (by polymer use), speeding up osteointegration (by bioactive glass use), antimicrobial effect (by antibiotics use) and decreasing of the implant price (by cheaper stainless steel use). The behaviour of polymer-antibiotic-glass/stainless steel structure in condition which simulates the physiological environment was evaluated in vitro by complementary techniques. The bioactivity and the release of the antibiotic were assessed by immersion into simulated body fluid and monitoring by FTIR and UV-VIS spectrometry and electrochemical measurements involving corrosion and EIS studies were carried out in order to investigate the corrosion resistance. The biological properties were tested including the microbial viability using Gram - and Gram + bacterial strains, the microbial adherence and the cytotoxicity on eukariotic cell.

V.V II.9
17:30
Authors : 1.Ana Maria Niculescu,2.Claudiu T.Fleaca, 3.Monica Scarisoreanu, 4.Marius Dumitru , 5.Catalin Luculescu, 6.Maria Dinescu , 7.Ion Morjan
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania , 2 1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania and "POLITEHNICA"University of Bucharest,Physics Department , Independentei 313 , Bucharest, Romania , 3National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania , 4.1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania , 5.National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania , 6.1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania , 7.1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania

Resume : The aim of this work is to compare two nanopowders obtained with different methods deposited by laser techniques. Mixed oxide nanoparticles containing different Ti:Sn atomic ratio were synthesized starting from sensitized mixtures of TiCl4 and Sn(CH3)4 precursors using laser pyrolysis technique. Tin oxide-based nanocomposites were obtained by glycine combustion technique starting from organometallic titanium tetraizoporpoxide and tetrabutyl-bis(acetyloxi) distanoxane. Structural and morphological properties of the obtained nanoparticles have been characterized by small particle sizes and structural homogeneity using XRD and TEM. Both anatase and rutile phases were identified in the resulted nanoparticles. The nanopowders were dispersed in aqueous media at different concentration using ultrasonication. Their hydrodynamic size distributions were evaluated before deposition by DLS (Dynamic Light Scattering). The water-based mixtures were frozen in liquid nitrogen and deposited using MAPLE (Matrix Assisted Pulsed Laser Evaporation) on silicon substrates and interdigitated electrodes. The thin films deposited on silicon substrates were analysed using TEM, XRD, SEM and EDX techniques. The obtained thin films deposited on interdigitated electrodes were tested at different gases. The electrical measurements were performed during heating process using different gas flows, starting from 5000 ppm until 100 ppm. The temperature range was around 300- 350 C, maintained for 3 hours at 350C.

V.V II.10
17:30
Authors : Ricardo Paupitz, Chad E. Junkermeier, Paulo S. Branicio, Adri C.T. van Duin
Affiliations : Departamento de Fisica, IGCE, Universidade Estadual Paulista, 13506-900, Rio Claro, SP, Brazil; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park PA 16802, USA; Institute of High Performance Computing, 1 Fusionopolis Way, \#16-16 Connexis, Singapore 138632, Singapore; Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park PA 16802, USA

Resume : Statical and dynamical aspects of a class of macromolecules based on the architecture of the well known fullerenes is theoretically investigated. The building blocks used to geometrically construct these molecules are the two dimensional structures: porous graphene and biphenylene-carbon. Density Functional-based tight binding (DFTB) methods as well as reactive molecular dynamics (ReaxFF) methods are applied to study the electronic and structural properties of these molecules. Our calculations predict that these structures can be stable up to temperatures of 2500K. The atomization energies of carbon structures is predicted to be in the range 0.45 eV/atom to 12.11 eV/atom (values relative to the C60 fullerene), while the BN analogues have atomization energies between -0.17 eV/atom and 12.01 eV/atom (compared to the B12N12 fullerene). Due to their high porosity, these structures may be good candidates for gas storage and/or molecular encapsulation. This possibility of encapsulation is explored using DFTB methodology. For this end, several DFTB based molecular dynamics simulations were carried in order to obtain new insights regarding mechanisms involved in the possible encapsulation of small molecules by these compounds.

V.V II.11
17:30
Authors : M.C. Spadaro1,2, S. D?Addato1,2, F. Benedetti1,2, G. Gasperi1,2, P. Luches2,V. Grillo2,3, G. Bertoni3,4, S. Turner5, G. Van Tendeloo5 and S. Valeri1,2
Affiliations : 1 Dipartimento FIM, Universit? di Modena e Reggio Emilia, via G. Campi 213/a, Modena, Italy 2 CNR-NANO, S3 Research Centre, via G. Campi 213/a, Modena, Italy 3 CNR-IMEM, Parco Area delle Scienze 37/A - 43124 Parma, Italy 4 Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy 5 EMAT, University of Antwerp, Antwerp, Belgium

Resume : CeO2-x nanoparticles (NPs) is a widely studied system because of its ability to store and release oxygen depending on the ambient conditions because of the switch between the Ce3 and Ce4 chemical states. Because of this ability, ceria is important in industrial catalysis, fuel cells and in biomedical applications to prevent the oxidation of human cells. In our work CeO2-x NPs were obtained with a gas aggregation source with a magnetron and a quadrupole mass filter. We oxidized the samples in different conditions in order to select the best oxidation procedure in terms of reducibility [(a)NPs deposited in vacuum (without oxygen), (b) deposition in oxygen atmosphere inside the deposition chamber and post oxidation and (c) deposition in oxygen atmosphere inside the aggregation chamber]. Then, in order to evaluate the contribution of the exposed planes to the NPs reducibility, we compared the reducibility of these NPs with the CexO2-x epitaxial islands ones (CexO2-x epitaxial islands were grown with the same aspect ratio as the NPs) exposing the (111) planes. Successively, we performed a study on how NPs reducibility is related with NPs size, producing NPs with an average diameter of 6 nm, 9 nm and 15 nm, varying power to the magnetron, Ar gas flow and aggregation tube length. On those systems we performed also SEM analysis to investigate their morphology, and in order to gain a deeper insight into the atomic structure and oxidation state of single NPs we performed some HR-TEM

V.V II.12
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10:10
Authors : Alexander Leitner, Verena Maier, Peter Hosemann, Daniel Kiener
Affiliations : Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben, Austria; Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, A-8700 Leoben, Austria; Department of Nuclear Engineering, University of California, Berkeley 4155 Etcheverry Hall, MC 1730, Berkeley, CA 94720-1730, USA; Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben, Austria

Resume : Current trends regarding design and engineering of highly efficient miniaturized devices and machines require innovative materials to satisfy requirements such as high strength at low density. The purpose of the present study was to investigate mechanical properties and deformation behavior of nanoporous Au and its ultra-fine grained bulk counterpart, both fabricated from the same base material. Microstructural investigations of the foam showed a ligament size of ~100 nm consisting of ~60 nm diameter grains in average, while the ultra-fine grained Au exhibits an average grain size of 250 nm. Nanoindentation lends itself as the method of choice to obtain local materials properties, at room temperature as well as at elevated temperatures, respectively. We performed a series of indentation tests and nanoindentation relaxation experiments to determine hardness, Young’s modulus, strain-rate sensitivity, and activation volume from room temperature to elevated temperatures up to 300 °C for the porous and bulk materials. Due to the small characteristic dimensions in terms of grain size or ligament diameter, high hardness values were determined for both materials, which rapidly drop at elevated temperatures. In addition, an enhanced strain-rate sensitivity accompanied by low activation volumes was determined, increasing with temperature for both states. We associate this mechanical behavior with interactions between dislocations and grain boundaries or free surfaces, respectively.

V.9.4
 
Session 10 : chair Pang Chi Lun
11:00
Authors : E. Khestanova [1], N. Dix [1], I. Fina [1], J.M Rebled [1,2], C. Magen [3], S. Estrade [2], F. Peiro [2], J. Fontcuberta [1] and F. Sanchez [1]
Affiliations : [1] Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Spain; [2] LENS - MIND/IN2UB, Universitat de Barcelona, Spain; [3] Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA) – ARAID , Zaragoza, Spain

Resume : Superlattices (SPLs) consisting of ferroelectric/paraelectric oxide layers present a large interest due to their flexibility for tuning of ferroelectric properties. In such SPLs a large number of interfaces are present, and additionally the lattice strain in the SPLs can differ notably with respect to single phase films. Discerning between strain and interface effects on the ferroelectric properties constitutes a bottleneck. We have fabricated BaTiO3/SrTiO3 (BTO/STO) SPLs by pulsed laser deposition (PLD) assisted by high pressure reflection high energy electron diffraction (RHEED). RHEED and atomic force microscopy confirm persistent layer-by-layer and atomically flat surfaces in complex M x (n-BTO / n-STO) SPLs, with period n from 1 to 10 and M adjusted to have total of 120 monolayers. X-ray reflectivity and X-ray diffractometry (XRD) patterns show Kiessig and Laue fringes signaling the high quality of the samples. XRD reciprocal space maps and high resolution transmission electron microscopy confirmed coherent growth. Polarization loops were measured, with remnant polarization (Pr) from a few μC/cm2 to more than 20 μC/cm2, increasing (decreasing) with the number of interfaces (STO thickness in each period). We present a thin film growth strategy that permits changing lattice strain for a fixed M x (n-BTO / n-STO) SPL architecture, and we show that Pr is much less sensitive to lattice strain than to the number of interfaces.

V.10.1
11:50
Authors : C. N. Mihailescu1, 2, E. Symeou1, R. Negrea3, C. Ghica3 and J. Giapintzakis1*
Affiliations : 1Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Avenue,PO Box 20537, 1678 Nicosia, Cyprus 2National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor Street, PO Box MG-36, 077125 Magurele, Romania 3National Institute of Materials Physics, RO-077125 Magurele, Romania

Resume : Vanadium dioxide (VO2) with its reversible metal-insulator transition (MIT) close to room temperature (341 K in single crystals) is attracting more and more interest due to the increasing number of applications in which it can be used. The constant and technologically relevant need of lowering its transition temperature (TMI) has resulted in an impressive number of theoretical and experimental studies investigating the influence of the substrate nature and crystallographic orientation, layer thickness, growing temperature, effect of doping, hydrogenation, interface quality, usage of an buffer layer or interfacial strain. Among them, the interfacial strain is considered as the most straightforward way to modulate the TMI. In this talk, we will present our recent results on VO2 thin films grown over a wide temperature range, and discuss the effect of interfacial strain on the TMI determined by electrical measurements. The films have been grown on low-miscut (0 0 1) TiO2 substrates by Pulsed Laser Deposition (PLD). Their crystal structure has been studied by high resolution X-ray diffraction (HR-XRD) and high resolution transmission electron microscopy (HR-TEM), while the quality of the interfaces (microstructure and stoichiometry) has been characterized by HR-TEM and Electron Energy Loss Spectroscopy (EELS). The strain nature of the films has been evaluated from HR-XRD and Geometrical Phase Analysis (GPA) measurements.

V.10.3
12:10
Authors : Sergiu V. Nistor, Mariana Stefan, Leona C. Nistor, Daniela Ghica
Affiliations : National Institute of Materials Physics, Atomistilor 105 bis, Magurele-Ilfov, Romania 077125

Resume : Ultrasmall zinc sulfide nanocrystals with cubic (blende) structure, doped with Mn2+ ions, have been prepared by colloidal synthesis [1] at pH = 8. According to XRD and HRTEM measurements they exhibit a core-shell structure, with a crystalline cZnS core of 2 nm average diameter and a shell of disordered, orthorhombic e-Zn(OH)2 of 0.3 to 1.9 nm thickness [2]. The analysis of the electron paramagnetic resonance spectra of the low concentration Mn2+ ions used as local atomic probes during pulse annealing experiments [3] resulted in the observation of a three-steps thermal decomposition of the e-Zn(OH)2 shell into nanostructured ZnO, in the 80-450 oC range, instead of a direct decomposition into crystalline ZnO at 120 oC, observed for the crystalline bulk e-Zn(OH)2 shell. This unusual behavior is explained by the sequential decomposition by dehydration of the disordered Zn(OH)2 shell into two new intermediate oxyhydrated Zn nanocompounds, which are not stable in the bulk form. Our results demonstrate that the chemistry of nanosized compounds can be different from the chemistry of the bulk counterparts. [1] S. V. Nistor et al., Superlattices Microstruc. 46 (2009) 306 [2] S. V. Nistor et al, J. Chem. Phys. C 42 (2013) 2217 [3] S. V. Nistor et al., J. Therm. Analys. Calorim. 118 (2014) 1021

V.10.4
16:30
Authors : E. Symeou 1, C. N. Mihailescu 1, 2, M. Pervolaraki 1 and J. Giapintzakis1
Affiliations : 1. Nanotechnology Research Center and Department of Mechanical and Manufacturing Engineering, University of Cyprus, 75 Kallipoleos Av., PO Box 20537, 1678 Nicosia, Cyprus ;2. National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor St., PO Box MG-36 077125, Magurele, Romania

Resume : Nowadays there is a strong belief that thermoelectric thin film-based devices represent a suitable route to mitigate thermal management problems in micro- and nano-electronics. Bi0.5Sb1.5Te3 (BST) is considered to be a state-of-the-art p-type thermoelectric material, at temperatures near room temperature, due to its high power factor value. Nevertheless, the deposition of BST thin films with bulk-like thermoelectric properties remains a challenge because of issues related to stoichiometry and antisite defects. There is still a need for investigating the effect of chemical compositions on the thermoelectric properties of BST thin films. We have grown p-type Bi0.5-xSb1.5Te3+x thin films onto different types of substrates using pulsed laser deposition at 248nm and home-made targets with different Bi concentrations, and investigated their structural, electrical and thermoelectrical properties. In this talk, we will present our recent results on Seebeck coefficient, electrical resistivity and Hall carrier concentration as a function of temperature for a series of Bi0.5-xSb1.5Te3+x thin films. We will discuss how their thermoelectric properties are affected by the substrate type and Bi content. Also, we will address the effect of post-annealing treatment on their structural and thermoelectric properties.

V.12.2
16:50
Authors : Antonio Cammarata, Tomas Polcar
Affiliations : Czech Technical University in Prague, Department of Control Engineering, Czech Republic; Czech Technical University in Prague, Department of Control Engineering, Czech Republic and Engineering Materials & nCATS, FEE, University of Southampton, United Kingdom

Resume : One of the main difficulties in understanding and predicting frictional response is the intrinsic complexity of highly non-equilibrium processes in any tribological contact, which include breaking and formation of multiple interatomic bonds between surfaces in relative motion. To understand the physical nature of the microscopic mechanism of friction and design new tribologic materials, we conducted a systematic quantum mechanic investigation at the atomic scale on the geometric, electronic and dynamic properties of prototipical MX2 (M=Mo, W; X=S, Se, Te) Transition Metal Dichalcogenides under variable load. We have been able to disentangle the electro-vibronic contribution to the frictional response by adopting a new investigation protocol: we combined the structural and dynamic information from group theoretical analysis and phonon band structure calculations with the characterisation of the electronic features using non-standard methods like orbital polarization and the recently formulated bond covalency and cophonicity analyses. The vibrational modes relevant during tribological conditions are individuated, quantified and put in relation with the atomic types and the electronic features that the latter determine. Guidelines on how to engineer macroscopic friction at nanoscale are formulated, and finally applied to design a new Ti-doped MoS2 phase. The formulated protocol can be promptly applied to the design of new materials with diverse applications other than tribology.

V.12.3

No abstract for this day


Symposium organizers
Maria DINESCUNational Institute for Lasers, Plasma and Radiation Physics

409 Atomistilor 77125 Magurele (Bucharest) Romania

+4021 457 44 14
dinescum@nipne.ro
Ioannis (John) GIAPINTZAKIS Nanotechnology Research Center and Department of Mechanical & Manufacturing Engineering | University of Cyprus

75 Kallipoleos Av. PO Box 20537 1678 Nicosia Cyprus

+357 22892283
giapintz@ucy.ac.cy
Marek WÓJCIK Institute of Physics, Polish Academy of Sciences

Al. Lotnikow 32/46 02-668 Warszawa Poland

+48 22 843 52 12
wojci@ifpan.edu.pl
Sergio D’ADDATO CNR-NANO and Dipartimento FIM Università di Modena e Reggio Emilia

via G. Campi 213/a 41125 Modena Italy

+39-059-2055254
sergio.daddato@unimore.it