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Nanomaterials

E

Defect-induced effects in nanomaterials

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The symposium addresses intriguing possibilities of tailoring different properties of low-dimensional and nano-materials in controlled manner by introducing dopants (e.g. implantation) or creating growth- and radiation -induced defects. The latest achievements in theory and experiment will be presented and discussed by academic and industrial researchers.

 

Scope:

Extensive research of radiation-, implantation- and growth-induced defects in materials has led to many important technological applications. Point and extended defects have been shown to notably affect the materials properties. The high sensitivity of modern technologies at submicron scale has promoted the exciting opportunity of developing new advanced materials with reduced dimensionality. This opens new prospects for ion and electron beam applications. Ion tracks and other radiation-induced effects provide the means for controlled synthesis and modification of materials of reduced dimensionality, such as nanoclusters and nanowires, allowing for efficient nano- and optoelectronic devices. Defect behavior in nanomaterials and nanostructures in its turn has often been found to differ substantially from that observed in bulk materials. Recent work has demonstrated spectacular optical and magnetic effects due to deliberately created defects or radiation-induced transformation of nanomaterials as well as radiation-induced displacements in low-dimensional insulators and semiconductors, with numerous potential applications. We plan to discuss, how such defects could be introduced controllably, categorized and controlled in nanostructures. Understanding and controlling defect properties in a wide class of advanced nanomaterials (2D structures, multiferroics, quantum dots and wires, etc.) could well be a key to breakthroughs in several crucial areas of science and technology. This is the main focus of the symposium.

 

Hot topics to be covered by the symposium:

  • Swift heavy ion irradiation as the means to tailor nanomaterials
  • Effects of grain boundaries and interfaces on the diffusion and transport processes in nanomaterials.
  • Electronic structure of defects in nanostructures; consequences for carrier transport, magnetism, optical and electronic properties, as well as device parameters.
  • Creation, evolution and properties of radiation defects in nanosize materials and heterostructures; the role of interfaces, nonstoichiometry, strain and adjacent layers.
  • Defects in two-dimensional materials.
  • Use of defects as microprobes.
  • Multiscale computer modeling of defect creation in nanomaterials.
  • Novel technological processes of micro-, nano- and optoelectronics using defects and radiation effects in nanostructures.

 

List of invited speakers (confirmed):

  • Eduardo Alves, Instituto Superior Tecnico (IST), Portugal: Radiation defects in low dimensional structures.
  • Tiziana Cesca, Padova University, Italy: Enhanced optical functionalities in silica by doping with Au-based nanostructures
  • Aurélien Debelle, Institut National de Physique Nucléaire et de Physique, France: Experimental and computational investigation of the defects involved in ion-beam-induced amorphization and recrystallization phenomena in SiC
  • Feng Ding, Institute of Textiles and Clothing, Hong Kong Polytechnic University, China: Formation of defects and defect healing during carbon nanotube and graphene growth
  • Anatoly V. Dvurechenskii, Institute of Semiconductor Physics, Russia: The point and extended defect induced nucleation and growth of quantum dots nanoheterostructures
  • Arkady Krasheninnikov, Aalto University, Finland: Native and irradiation-induced defects in graphene and inorganic 2D materials
  • Claudine Noguera, Université Pierre et Marie Curie, France: Polarity driven defect formation in oxide nanomaterials
  • Kai Nordlund, University of Helsinki, Finland: Mechanism of He impurity buildup-induced nanopore and fuzz formation in W
  • Sokrates T. Pantelides, Vanderbilt University, USA: Defects in two-dimensional materials and nanoparticles
  • Ricardo Papaleo Pontificia, Univ. Catolica Rio Grande do Sul, Brazil: Confining ion tracks in 2D organic materials: the case of ultrathin polymer layers
  • Christina Trautmann, GSI Helmholtz Zentrum, Germany: Novel nanowire and nanotube structures produced by ion-track technology
  • Andre Vantomme, KU Leuven, Belgium: Superconductivity of implanted Pb precipitates
  • Blas Uberuaga, Los Alamos NL, USA: The evolution of radiation damage within oxide nanocomposites
  • William J. Weber, University of Tennessee, USA: Irradiation Response of Nano-Engineered SiC
  • Yanwen Zhang, Oak Ridge NL, USA: Defect-induced effects in nanocrystalline oxides and carbides
  • Shengqiang Zhou, Helmholtz - Zentrum Dresden - Rossendorf, Institute of Ion Beam Physics and Materials Research, Germany: Ion beam synthesis of the full spectrum of III-V:Mn ferromagnetic semiconductors

 

Registration fee waivers:

There will be a limited number of graduate assistantships (conference fee waivers) to allow students performing PhD work to present a poster.

The deadline for the Student Grant (conference fee waiver) request is April 8, 2014.

To be eligible, students must be actively pursuing a PhD degree.

To apply for a conference fee waiver, they have to do the following:
- Submit a regular abstract of the subject they will present in a Symposium E session
- Send to the email address nanodefects@gmail.com a short application (see below), accompanied by a scanned-in letter of support from the thesis advisor and a certificate of the university registration. - The letter of support and certificate must be transformed into the pdf format.
- The subject of the email should be as follows: "Grant application_SympE 2014_Familyname_Name"

 

Preference will be given to students nearing completion of their thesis work.

Student Grant application form (email body):
First Name:
Last Name:
Institution:
City, Country:
Authors and title of the submitted abstract:
Title of the thesis in preparation:
Name and affiliation of the thesis advisor:
E-Mail:
   

 

Proceedings:

The conference proceedings will be published in physica status solidi (c). Excellent manuscripts will be selected for physica status solidi (a). The online submission for the conference proceedings is now open:
http://mc.manuscriptcentral.com/pssc

The submission will be accepted ONLY online. The submission deadline is May 30, 2014.

For any question do not hesitate to contact nanodefects@gmail.com.

 

Sponsor:

 

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Symposium organizers:

 

Flyura Djurabekova
Helsinki Institute of Physics and Department of Physics
University of Helsinki
PB 43
00014 Helsinki
Finland
Phone: +358 9 19150084
Fax: +358 9 19150042
flyura.djurabekova@helsinki.fi

 

Eugene Kotomin
Institute of Solid State Physics
University of Latvia
Kengaraga 8
Latvia
Phone: +371 67187480
Fax: +371 67132778
kotomin@latnet.lv

 

Mark C. Ridgway
Australian National University
Canberra ACT 0200
Australia
Phone: +61 2 6125 0519
Fax: +61 2 6125 0511
Mark.Ridgway@anu.edu.au

Nikolai A. Sobolev
Departamento de Física
Universidade de Aveiro and I3N
Campus de Santiago
3810-193, Aveiro
Portugal
Phone: +351 234 378117
Fax: +351 234 378197
sobolev@ua.pt

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Properties of graphene : Arkady Krasheninnikov
09:00
Authors : Sokrates T. Pantelides, Stephen J. Pennycook
Affiliations : Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA and Oak Ridge National Laboratory, Oak Ridge, TN USA; University of Tennessee, Knoxville, TN USA

Resume : Calculations based on density functional theory using high-performance computers have made enormous strides in describing the atomic-scale properties of complex materials. In parallel, aberration-corrected scanning transmission electron microscopy has reached extraordinary levels of spatial and energy resolution, in both imaging and electron-energy-loss spectroscopy. The combination of theory and microscopy provides an unparalleled probe of the atomic-scale structure, properties, and dynamics of complex systems, especially defects, boundaries, interfaces and nanoparticles. Here we describe recent results on defects in graphene, MoS2 monolayers, and CuInS2 nanoparticles. More specifically, we will discuss plasmon enhancement at Si impurities in graphene [1], Si6 clusters and Si-passivated nanovoids in graphene [2], nanowire formation in MoS2 monolayers [3], and a unique form of crystalline order observed in CuInS2 nanoparticles [4]. Primary collaborators: Theory: Jaekwang Lee, Xiao Shen, Junhao Lin; microscopy: Wu Zhou, Juan C. Idrobo, Junhao Lin, Matt Chisholm; This work was supported by the US Department of Energy Basic Energy Sciences, Materials Science and Engineering directorate. 1. W. Zhou et al., “Atomically localized plasmon enhancement in monolayer graphene”, Nature Nanotechn. 7, 161 (2012). 2. J. Lee et al., Direct visualization of reversible dynamics in a Si6 cluster embedded in a graphene pore, Nature Commun. 4, 1650 (2013); J. Lee et al. “Stabilizaion of graphene nanopores”, under review. 3. J. Lin et al., “Flexible metallic nanowires with self-adaptive contacts to semiconducting transition-metal dichalcogenide monolayers”, under review. 4. X. Shen et al., “Interlaced crystals: ‘Perfect Bravais lattices with interlaced chemical order revealed by real-space crystallography”, under review.

E.EO1.1
 
Two-dimensional materials : Sokrates Pantelides
10:30
Authors : Arkady V. Krasheninnikov
Affiliations : Department of Applied Physics, Aalto University, Finland

Resume : Following the isolation of a single sheet of graphene, many other 2D systems such as h-BN, transition metal dichalcogenides (TMD), and SiO2 sheets were later manufactured. All these materials have native defects, which naturally affect their properties. Moreover, defects can deliberately be introduced by ion and electron irradiation to tailor the properties of 2D materials. In my talk, I will summarize our knowledge about defects [1,2] in graphene and other 2D systems. I will also touch upon defect production in 2D systems under impacts of energetic ions and electrons and present theoretical data obtained in collaboration with several experimental groups [3-6]. I will also dwell upon impurity and defect-mediated engineering of the electronic structure of 2D materials such as BN or TMDs. I will finally touch upon defects in bilayer 2D silica [8] and show that point and line defects in this system are strikingly similar to those in graphene with their morphology being governed by the hexagonal symmetry of the lattice. 1. F. Banhart, et al. ACS Nano, 5 (2011) 26. 2. O. Lehtinen et al. Nature Comm. 4 (2013) 2098. 3. M. Kalbac, et al. Adv. Mat. 25 (2013) 1004. 4. J. Meyer, et al. PRL 108 (2012) 196102. 5. H.-P. Komsa, et al. PRL 109 (2012) 035503; PRB 88 (2013) 035301. 6. R. R. Nair, et al. Nature Comm. 4 (2013) 2010. 7. Y. Lin et al. Adv. Mat. (2014) accepted. 8. T. Björkman et al. Sci. Rep. 3 (2013) 3482.

E.EO2.1
11:00
Authors : A. Zobelli, R. Bourellier, M. Amato, L.H.G. Tizei, C. Giorgetti, A. Gloter, M.I. Heggie, K. March, O. Stephan, L. Reining, M. Kociak
Affiliations : Laboratoire de Physique des Solides, Univ. Paris-Sud, CNRS UMR 8502, F-91405, Orsay, France; Laboratoire des Solides Irradies, Ecole Polytechnique, Route de Saclay, F-91128 Palaiseau and European Theoretical Spectroscopy Facility (ETSF), France; Department of Chemistry, University of Surrey, Guildford GU2 7XH, United Kingdom

Resume : The strong excitonic emission of hexagonal boron nitride (h-BN) makes this material one of the most promising candidate for light emitting devices in the far ultraviolet (UV). However, single excitons occur only in perfect monocrystals that are extremely hard to synthesize, while regular h-BN samples present a complex emission spectrum with several additional peaks. Despite a large number of experimental and theoretical studies, the microscopic origin of these additional emissions has not yet been understood. In this work we address this problem using an experimental and theoretical approach that combines nanometric resolved cathodoluminescence, high resolution transmission electron microscopy and state of the art theoretical spectroscopy methods. We demonstrate that emission spectra are strongly inhomogeneus within individual h-BN flakes and that additional excitons occur at structural deformations, such as faceted plane folds, that lead to local changes of the h-BN stacking order.

E.EO2.2
11:15
Authors : Sivacarendran Balendhran,* Sumeet Walia, Jian Zhen Ou, Sharath Sriram, Madhu Bhaskaran, and Kourosh Kalantar-zadeh,
Affiliations : Functional Materials and Microsystems Research Group, School of Electrical and Computer Engineering, RMIT University, Melbourne, Australia

Resume : Since the discovery of graphene, exploration of alternative 2D materials with intrinsic bandgap for electronic applications has been afoot. Layered MoO3 has a relative high dielectric (k) of ~500 and can be exfoliated to minimum resolvable 2D layers. The bandgap of MoO3 can be easily manipulated to desirable values by several techniques such as hydrogen ion intercalation, UV irradiation, electron beam bombardment etc. Such techniques produce partially reduced non-stoichiometric MoO(3-x) which has increased carrier concentration and a high-k value, that highly favours the enhancement in charge carrier mobility. In this work, room temperature charge carrier mobilities exceeding ~1100 cm2/Vs were established for non-stoichiometric 2D MoO3 based field effect transistors (FETs). The experimental mobilities and the theoretical behaviour of the mobility, calculated using Borne approximation with respect to temperature are presented. As, the acoustic and optical phonon scattering effects are independent of the k value, in a low-k material coulomb scattering effect seems to be the limiting mechanism of the overall mobility. In a high-k material the coulomb scattering effect is minimized and acoustic phonon scattering emerges as the dominant mechanism that limits the overall mobility. The experimental mobilities observed in the MoO(3-x) FET are in the same order of magnitude and closely match the theoretically predicted trend of the overall mobility. In summary, this work demonstrates the enhancement of the overall carrier mobility in a high-k 2D material, achieved by introducing non-stoichiometry.

E.EO2.3
 
Nanoheterostructures : Andre Vantomme
14:00
Authors : A.V.Dvurechenskii
Affiliations : Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Science, Novosibirsk State University

Resume : The aim of the present work is to review present and future trends of research on quantum dot (QD) nanostructured semiconductors concerning quantum dot molecules (QDM), from fundamental issues of synthesis to some electronic properties. The synthesis should allow: a) to improve QD homogeneity in size with keeping form and elemental content; b) to control QD density and space ordering; c) to lower the defect density. Spontaneous nucleation of nanocrystals at heteroepitaxy of lattice mismatched semiconductors is described by: a) the dispersion in size averaged with 17-20% for (as example) Ge QD in Si; b) the random nanocrystal nucleation and as a result random arrangement in growth plane. Different experimental techniques such as the nanoimprint, extreme ultraviolet interference, electron-beam lithography, ion-beam induced pit-patterning of substrates and effect of vertical alignment of nanocrystal nucleation are used for the fabrication of templates with predefined dot formation sites. The epitaxy on pin-patterned surface allows to reduce QD size dispersion and QD ordering in the plane of growth. Another way of QDM growth is the strain induced epitaxy in heterophase system. The spatial localization of electrons in QDM can be controlled by the change of spacer thickness between double QDM. The two-qubit operations are performed on the physical qubits by controlling the exchange interaction. There were determined the conditions on which the exchange coupling is large enough for a fast swap operation in quantum computation and the double-occupancy probability is still low, thus maximizing the entanglement for a small computation error which allows to use coupled Ge/Si QDM in two-qubit quantum operations.

E.EO3.1
16:00
Authors : Minoru Fujii, Hiroshi Sugimoto, Takashi Kanno, Masataka Hasegawa, and Kenji Imakita
Affiliations : Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan

Resume : Colloidal Si nanocrystals have been attracting significant attention because they can be a key material for Si-based printable electronics and are expected to be more suitable for biological applications than compound semiconductor nanocrystals due to the non-toxicity as a chemical element. In general, the surface of Si nanocrystals is functionalized by organic ligands to prevent the agglomeration in solution. However, the surface molecules hinder charge carrier transport in films produced from colloidal solutions. Recently, we have developed Si nanocrystals which can be dispersed in polar solvents without organic ligands. The structural feature of the nanocrystal is the formation of a heavily B and P doped shell on the surface. The core-shell Si nanocrystals exhibit very wide range tunable luminescence (0.85-1.8eV) in solution due to the donor to acceptor transitions. In this work, we study the structure of the heavily B and P doped shells by Raman scattering and X-ray photoelectron spectroscopies. We demonstrate the evidences that a thin hard crystalline shell containing different kinds of B and P related species, e.g., substitutional B, P and B-P pairs, B clusters, B-interstitial clusters, etc., are formed on the surface of a nanocrystal. We also show that the method can be applied to SiGe alloy nanocrystals. SiGe alloy nanocrystals dispersible in ethanol without organic ligands and exhibiting size and composition controllable photoluminescence can be produced by the method.

E.EP1.3
16:00
Authors : Stephane NEUVILLE
Affiliations : TCE

Resume : Considering that sp2 clusters imbedded in amorphous carbon material correspond to graphenic particles, Raman results achieved with graphene are expected to provide improved insight of many carbon materials and in order to check abundance of atomic point defects in form of vacancies and voids in graphene, SWCNT and DLC materials. However, in spite of significant progress achieved, many Raman results remain confusing especially concerning the so-called ?D disorder? Raman peak, the ?2D? band and some side peaks of the ?G? peak of graphene. Analyzing in more details current double resonance (DR) theory used for graphene Raman peak assignment and associating them to published results achieved with Micro-Raman, some questions suggest that commonly used assumptions need to be modified. This is especially concerning the locality principle of the corresponding Raman scattering model for which energy and momentum conservation conditions are not always fulfilled. Basing on dual quantum mechanical/classical representation of electron and phonon, we propose a Coupled Double Resonance theory (CDR) with which we discuss why some intense ?2D? peak can be observed where no ?D disorder? peak exists suggesting then, contrary to what established theory claims that the ?2D? is not only corresponding to a second harmonic overtone of the so called ?D disorder? peak of graphene at ~1350 cm-1 and why no second harmonic overtone of the G peak has never been observed. These effects can be used to depict the existence of point defects in graphene and SWCNT and to sort out the paradoxical case where the so-called ?D disorder? peak is superimposed by some stress upshifted ?D diamond? peak in glassy carbon for instance, which is known to contain significant amounts of voids.

E.EP1.5
16:00
Authors : Do Van Lam,1, 2 Sang-Min Kim,2 Youngji Cho,3 Jae-Hyun Kim,2 Hak-Joo Lee,2 Jun-Mo Yang, 3 Seung-Mo Lee 1, 2, *
Affiliations : 1 Nano Mechatronics, University of Science and Technology (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 305-333, South Korea 2 Department of Nanomechanics, Korea Institute of Machinery and Materials (KIMM), 156 Gajeongbuk-ro, Yuseong-gu, Daejeon 305-343, South Korea 3 Department of Measurement & Analysis, National Nanofab Center, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea

Resume : Structural defects present on chemical vapor deposition (CVD)-graphene are usually originated from growth stage and transfer process. Those limit the electronic transport properties of the graphene and degrade performance of related devices. Here we report that those inherent atomic defects could be selectively healed by simple vapor phase treatment performed in equipment conventionally used for atomic layer deposition (ALD). The unique chemistry of Al2O3 ALD facilitated selective depositions of AlxOy compounds on the defects, which was able to be readily probed and visualized using AFM imaging. The healing agent, AlxOy, was observed to bind tightly to the defects and lead to doping of the CVD-graphene, which were reflected in noticeable improvement in the electrical sheet resistance. In contrast with the chemically doped graphene, the ALD treated graphenes revealed notable long term stability under environmental conditions. Our approach promises selective healing of defects present in most of materials and likely ensures considerable enhancement in electrical and mechanical properties. The ALD with a broad spectrum of material selection could be a versatile tool for upgrading materials’ properties.

E.EP1.10
16:00
Authors : Pascal Pochet 1 ; Eduardo Machado-Charry 1 ,2 ; Paul Boulanger 1 ; Luigi Genovese 1 and Normand Mousseau 3
Affiliations : 1 Laboratoire de simulation atomistique (L_Sim), SP2M, INAC, CEA-UJF, Grenoble, F-38054, France 2 Nanosciences Fondation, 23 rue des martyrs, 38000 Grenoble, France 3 Departement de Physique and RQMP, Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, Quebec H3C 3J7, Canada

Resume : Magnetism in two dimensional atomic sheets has attracted considerable interest as its existence could allow the development of electronic and spintronic devices. The existence of magnetism is not sufficient for devices, however, as states must be addressable and modifiable through the application of an external drive. We show that defects in hexagonal boron nitride present a strong interplay between the N-N distance in the edge and the magnetic moments of the defects. By stress-induced geometry modifications, we change the ground state magnetic moment of the defects [1]. This control is made possible by the triangular shape of the defects as well as the strong spin localisation in the magnetic state. [1] E. Machado-Charry et al. Appl. Phys. Lett. 101 132405 (2012) ; http://dx.doi.org/10.1063/1.4754143

E.EP1.14
16:00
Authors : D. Untila*, V. Canţer**, M. Caraman*, I. Evtodiev*, L. Leontie***, L. Dmitroglo*
Affiliations : * The Laboratory of Scientific Research Photonics and Physical Metrology, Moldova State University, A. Mateevici, 60, MD-2009 Kishinev, Republic of Moldova; ** Institute of the Electronic Engineering and Nanotechnologies, Academy of Sciences of Moldova; *** Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Bul. Carol I, Nr. 11, 700506 Iasi, Romania

Resume : By Cd-vapor heat treatment, at temperatures from 500 to 600°C, of GaSe and GaSe:Eu single crystals, GaSe-CdSe and GaSe:Eu-CdSe composites were obtained. The composite contains both GaSe micro- and nanolamella and CdSe microcrystallites, which presence were confirmed by XRD patterns. GaSe lamella (001) surface nanostructuration morphology is well highlighted in AFM images. In this paper photoluminescent properties of GaSe-CdSe and GaSe:Eu-CdSe composites were investigated at 78-300K temperature range. In photoluminescence (PL) spectrum of GaSe lamella, at temperatures T ≤80K, the exciton emission band is prevailing. The energy position of the n=1 exciton peak is 2.11 eV. In PL spectrum of GaSe:Eu lamella, additional to GaSe characteristic particularities, Eu3+ emission bands are present, with peak localized at 2.2 eV. GaSe-CdSe composite emission spectra contains both impurity emission band (maximum at 1.74 eV) and CdSe crystallites donor-acceptor emission band (maximum at 1.79 eV). Eu3+ center emission band, with maximum at 2.17 eV amplifies its intensity by ~1.5-1.7 times and obtains a larger contour than that of GaSe:Eu. CdSe crystallites presence leads to extinction of exciton band present in GaSe:Eu crystalls.

E.EP1.15
16:00
Authors : F. Komarov1, L. Vlasukova1, V. Yuvchenko1, A.Dauletbekova2, A. Akilbekov2, A. Alzhanova2
Affiliations : 1 Belarusian State University, Minsk, Belarus, 2L.N.Gumilyov Eurasian national university, Astana, Kazakhstan

Resume : Fast ion irradiation for formation of latent tracks in SiO2 is of great interest for practical applications. These tracks can be etched in appropriated etchants with the formation of nanochannels. For reproducible formation of layers with high density (up to 1011 cm-2) of nanochannels, it is very important to evaluate the crucial factors of track etching. Among these factors the most important ones are: probability of formation of the latent track around each incident ion and minimum size of pore, which may occur in the place of a latent track during etchant treatment. The effects of the fast ions passage through SiO2 and some other insulators are well described using the thermal spike model. It has been believed that the etchable track results from the quenching of a zone which contains the sufficient energy for melting. We have evaluated the possibility of nanochannel formation in amorphous SiO2 and Si3N4 during the irradiation with 19F 28 MeV; 32S 47 MeV; 35Cl 43 MeV, 40Ar 38, 54 MeV for SiO2 and with 56Fe 56 MeV, 84Kr 84 MeV, 180W 180 MeV for Si3N4. For this purpose we calculated the molten region radius for ions named above using computer simulation in the frame of thermal spike model and compared it with the criterion for “etchability” of tracks from [1]. [1] A. Dallanora et al, J. Appl. Phys. 104 (2008) 024307.

E.EP1.18
16:00
Authors : A. Dauletbekova1, R. Zabels2, A. Russakova1, M. Baizhumanov1, A.Akilbekov1, M. Zdorovets1
Affiliations : 1L.N. Gumilyov Eurasian national university, Astana Kazakhstan, 2Institute of solid state physics, University of Latvia, , Riga, Latvia

Resume : Formation of single defects and bulk nanostructures in LiF crystals, irradiated with swift Au and Kr ions of different energy and dose under normal and oblique incidence, were investigated by AFM, SEM, optical spectroscopy (absorption and luminescence spectra), nanoindentation and thermal annealing. In case of normal ion beam incidence the two structural zones can be distinguished: one enriched with dislocations and another exhibiting features of mosaic-type bulk nanostructure. The observed effects have a threshold nature in terms of energy loss and fluence. The samples irradiated at angles other than normal have a similar division into zones, but are oriented in the direction of the ion beam. Variation in thickness of the irradiated layer in dependence on the angle of incidence can be observed. Thermal annealing enabled to estimate the thermal stability of nanostructures and thermal diffusion of anion vacancies, which actively participate in the process of aggregation of electronic color centers.

E.EP1.19
16:00
Authors : B.L.Oksengendler1), S.E.Maksimov1), O.B.Ismailova1), F.G.Djurabekova2)
Affiliations : 1)Institute of ion-plasma and laser technology, Uzbek Academy of Sciences, Tashkent, Uzbekistan; 2)Helsinki Institute of Physics and Department of Physics, University of Helsinki, Helsinki, Finland

Resume : The modification of basic radiation physics effects (elastic defect generation and amorphization) in quantum dots embedded in solid matrix, is theoretically considered. The diffusion model of formation of defects with U-negative properties is introduced, and the effect of the “quantum dot-matrix” border on the displacement energy is studied. The basic reasons why the critical dose for amorphization of quantum dots is different from the same for the bulk crystal it discussed based of percolation ideas. We show that there are regions in the quantum dot core where the probability of defect formation and hence amorphization is negligible, which explains the radiation stability of nanostructure. This phenomenon is related to radiation enhanced diffusion of interstitials proceeding through the Oksengendler-Bourgoin mechanism (1972). Some features of radiation physics of nanoobjects taking into account; the combination of elastic and athermal electron-enhanced defect processes are discussed.

E.EP1.25
16:00
Authors : V.V. Uglov1, G.E. Remnev2, N.T. Kvasov1, I.V. Safronov1
Affiliations : 1Belarusian State University,Minsk, Belarus; 2Tomsk PolytechnicUniversity, Tomsk,Russia

Resume : In this paper, on the basis of the electronicSe and nuclearSn cross sections braking proposed space-time description of the dynamics of motion of the accelerated ions in the medium.Received the analytical expressions for the ion velocityv(t) and displacementl(t) at an arbitrary time in the material volume. Comparison of the results of the theory, experiment and computer simulation shows their satisfactory agreement. Proposed the structure of the threshold energy of the defectEd. Also dynamical processes occurring in the nano-dimensional metal object during penetration of high-energy ions are studied in detail. It is shown that the elastic and thermoelastic response of the lattice to radiation exposure forms power factors that significantly affect on the evolution of defect-impurity system resulting in a decrease of a number of structure defects. A quantitative estimation of spatial distribution of defects resulting in their exit on the surface was made. Such self-organization of nanoparticles under ionizing radiation is the basis for the creation of nanostructured radiation-resistant materials capable to withstand a long-term intense radiation loads.

E.EP1.26
16:00
Authors : M. Vallet1, J. F. Barbot1, A. Declémy1, S. Reboh2, M. F. Beaufort1
Affiliations : 1Institut Pprime, UPR 3346 CNRS - Université de Poitiers - ENSMA, Department of Material Sciences, BP30179, 86962 Futuroscope Chasseneuil, France 2CEA-LETI, Minatec Campus, 17 rue des Martyrs, 38054 Grenoble, France

Resume : Helium implantation in Si is known to form ‘He-plates’. These defects are similar to H-platelets regarding to their general shape, but 10 to 20 times greater. Consequently, they are potential competitors to ‘H-platelets’ as precursors for the Smart-Cut® process. However, few studies have been focused on the characterization of these two dimensional defects. In this work, we present a study on the effect of the Si crystalline orientation on the implantation-induced strain/stress and on the formation of He-plates by combining high-resolution X-ray scattering and transmission electron microscopy. The highest strains are obtained onto (001)-oriented implanted substrates regardless of the fluence and of the channeling effects. Upon specific thermal annealing, the formation of He-plates was found to occur only in the {001} habit planes regardless of the orientation of the substrate. Moreover the distribution of He-plates in the {001} variants was found to be strongly dependent on the angle of the habit plane with the surface and on the intensity of the implantation-induced strain/stress. The nucleation and growth of He-plates are thus discussed with regard to the implantation-induced stress.

E.EP1.27
16:00
Authors : A.S. Nikolenko(1), V.V. Strelchuk(1), Yu.Yu. Stubrov(1), V.O. Gubanov(2), M.M. Biliy(2), L.A. Bulavin(2) and O.E. Belyaev(1)
Affiliations : (1) V. Lashkaryov Institute of Semiconductor Physics National Academy of Sciences of Ukraine, 45 Nauky pr., 03028 Kyiv, Ukraine (2) Kyiv National Taras Shevchenko University, Department of Physics, 64 Volodymyrs’ka str., 01601Kyiv, Ukraine

Resume : In the present work we used confocal micro-Raman spectroscopy as sensitive tool to study the nature of defects in single-layer graphene induced by laser irradiation at varied laser power densities and dozes. The minimal power threshold of the exciting radiation of the structural defects generation is found. Appearance and drastic intensity increase of zone-edge D-like modes caused by introduction of structural defects in the graphene layer were observed in the Raman spectra at higher powers of excitation. Time-dependent evolution of Raman spectra is studied. From the analysis of intensities of defective D and D’ bands relative to G-band, the structural defects generated under laser irradiation of graphene with power density higher than threshold are shown to be mainly vacancy-type defects [1]. The surface density of structural defects is estimated from the intensity ratio of D and G bands. Stokes and anti-Stokes components of the Raman spectra are analyzed to estimate the lattice temperature of graphene on the power density of exciting radiation. 1. Axel Eckmann et al., Probing the nature of defects in graphene by Raman spectroscopy. Nano Lett. 12, 3925-3930 (2012).

E.EP1.29
16:00
Authors : B. P. Falcão(1), J. P. Leitão(1), M. R. Correia(1), M. P. Leitão(2), M. V. B. Moreira(3), A. G. de Oliveira(3), F. M. Matinaga(3), J. C. González(3)
Affiliations : (1) Departamento de Física and I3N, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal (2) Departamento de Física and CICECO, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal (3) Departamento de Física, Universidade Federal de Minas Gerais, 30123-970 Belo Horizonte, Minas Gerais, Brazil

Resume : GaAs nanowires are promising building blocks for third-generation solar cells as they bring potential benefits over traditional wafer or thin-film based technologies, related mainly to cost, stronger light absorption, and charge separation mechanisms. To realize the full potential of such devices, the electronic doping of the nanowires and their optical and electrical transport properties must be controlled and thoroughly understood. Because GaAs nanowires can simultaneously crystallize in the wurtzite and zincblende structures, which influence strongly its electronic level structure, the investigation of these polytypic nanowires with different doping profiles is very important in view of future devices. Therefore, in this work, we present a report on the photoluminescence of Mg-doped GaAs nanowires and thin-films with different levels of doping. In the case of the thin-films, it is only observed a single radiative transition related to Mg acceptors that redshifts with increase concentration, due to the bandgap energy narrowing effect. The photoluminescence from individual nanowires and from a bunch of several hundreds of nanowires is analyzed over a wide temperature range, and is compared to that of the thin-films. It is found that in the nanowires the radiative transitions are critically influenced by the staggered type II band alignment, due to the existence of polytypic regions along the nanowires, and seems to be independent of the Mg concentration.

E.EP1.31
16:00
Authors : Carmen Coya1, Miguel García-Vélez1, Carmen Munuera2, Alicia de Andrés2, Angel Luis Álvarez1
Affiliations : 1-Escuela Superior de Ciencias Experimentales y Tecnología (ESCET), Universidad Rey Juan Carlos, 28933 Madrid, Spain; 2-Instituto de Ciencia de Materiales de Madrid, CSIC, 28049 Madrid.

Resume : Electric arc lithography performed at low continuous voltages has been recently proven as a successful dry patterning technique for thin films of different conductive materials in room conditions [1]. In this work, we show an application of this procedure to graphene single layers on SiO2(90 nm) / Si-p+ substrates, proving an efficient large area and cost effective patterning procedure for electronic device development, which prevents photoresists and insolation steps.Resolution of this technique (which is currently 10 um, as determined by the used probe diameter), and the influence of critical parameters such as operating voltage (in the range 10 – 60 V) and probe speed, are discussed. We observe that Interesting defects, such as graphene oxide or nanographene domains may be induced during the patterning process. We discuss here, by means of Raman spectroscopy and AFM studies, including both topographic and electrostatic force measurements, the relation between the observed features and the operating conditions. Also, a depth study of the electrical discharge generation at submicron scale, which allows optimizing the procedure, is discussed. [1] )J. Jimenez-Trillo,A. L. Alvarez,C. Coya,E. Céspedes,A. Espinosa, “The use of arc-erosion as a patterning technique for transparent conductive materials”, Thin Solid Films, 520 (4), 1318-1322 (2011).

E.EP1.35
16:00
Authors : Imed Ghiloufi1,2; Lassaad El Mir1,2
Affiliations : 1- Al Imam Mohammad Ibn Saud Islamic University (IMSIU), College of Sciences, Riyadh, Saudi Arabia. 2- Laboratory of Physics of Materials and Nanomaterials Applied at Environment (LaPhyMNE), Faculty of Sciences, Gabes University, Tunisia.

Resume : Nanoporous carbons (NPCs), based on organic xerogel compounds, were synthesized by sol–gel method from pyrogallol and formaldehyde (PF) mixtures in water using perchloric acid as catalyst. These NPCs were prepared at different pyrolysis temperatures 650 ºC (PF-650), 700 ºC (PF-700) and 1000 ºC (PF-1000) and they are doped by different oxides CuO (PF-CuO) and NiO (PF-NiO). The obtained NPCs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and nitrogen porosimetry. These nanomaterials were used to study the effect of pyrolysis temperatures of NPCs on the uptake of Cr, Ni, Cd and Co from aqueous solution. In this work the effect of the presence of CuO and NiO in the NPCs on the adsorption of heavy metals from aqueous solution has been studied.

E.EP1.38
16:00
Authors : Achintya Singha, Dipanwita Majumdar, Abhisek Basu, Goutam Dev Mukherjee, Daniele Ercolani, Lucia Sorba
Affiliations : Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700009, India; Department of Physics, Bose Institute, 93/1, Acharya Prafulla Chandra Road, Kolkata 700009, India; Department of Physical Sciences, IISER Kolkata 741252, India; Department of Physical Sciences, IISER Kolkata 741252, India; NEST-Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza S. Silvestro 12, I-56127 Pisa, Italy; NEST-Istituto Nanoscienze-CNR and Scuola Normale Superiore, Piazza S. Silvestro 12, I-56127 Pisa, Italy

Resume : One dimensional semiconductor nanowires (NWs) of diameter in the range of few to several tens of nanometer find their potential as building blocks for the next generation of miniaturized electronic and optoelectronic devices.1-3Among them, InAs NWs are of particular interest for excellent electron transport property due to their small effective mass. As a thermodynamic parameter external pressure plays an important role to tune electronic and structural properties of a system. In low dimensional systems, number of factors like defects, confinement, and surface tension are important to understand the pressure induced electronic and structural transformations. Therefore, the studies of semiconductor NWs under pressure are particularly important for their technological applications. High pressure Raman scattering is a powerful technique for extracting information regarding vibrational properties and phase diagrams of both bulk and nanostructures.4-6 Here, we have investigated the hydrostatic pressure response (up to 58 GPa) of TO, LO and other optical modes of predominant wurtzite InAs NWs in a diamond anvil cell.7All the observed phonon frequencies increase linearly while the LO-TO splitting decreases with pressure. 7 The recorded Raman modes have been used to determine the mode Grüneisen parameters and also the value of Born’s transverse effective charge ( ).7 The calculated exhibits a linear reduction with increasing pressure indicating an increase in covalency of NWs under compression.7A resonant Raman scattering is observed around 1.64 GPa due to increase of E1 band gap with applying pressure. A signature of structural phase transformation has been observed above pressure 10.87 GPa.7 We propose this transformation may be from wurtzite to rock salt phase although further experimental and theoretical confirmations are needed. References 1. W. Lu and C. M. Lieber, Nature Materials , 2007,6, 84. 2. S. W. Chung, J. Y. Yu, and J. R. Heath, Appl. Phys. Lett., 2000, 76, 2068. 3. P. J. Pauzauskie and P. Yang, Materials Today, 2006, 9, 36. 4. I. Zardo, S. Yazji, C. Marini, E. Uccelli, A. F. Morral, G. Abstreiter, and P. Postorino, ACS NANO, 2012, 6, 3284. 5. R. Trommer, E. Anastassakis, and M. Cardona, in Light Scattering in Solids, edited by M. Balkanski, R. C. C. Leite, and S. P. S. Porto, (Flammarion, Paris, 1976), p. 396. 6. D. Olego and M. Cardona Phys. Rev. B, 1982, 25, 1151. 7. D. Majumdar, A. Basu, G. D. Mukherjee, D. Ercolani, L. Sorba, A. Singha, arXiv:1401.2318[cond mat.mes-hall].

E.EP1.40
16:00
Authors : Orest Fl’unt
Affiliations : Faculty of Electronics, Ivan Franko National University of Lviv, Ukraine

Resume : Low-frequency dielectric and impedance spectroscopy is powerful characterization method of amorphous and disordered materials, partly amorphous chalcogenide and pnictide thin films. The widely known models of low-frequency ac conductivity and dielectric loss explains fractional power shape of frequency spectra via wide distribution of localized levels in the forbidden gaps or by random distribution of localized centers. But expected temperature dependencies of ac response and their parameters strongly depend on the model, however a universality of temperature behavior of ac response of amorphous materials is often observed. The proposed model of frequency and temperature dependencies of ac response of amorphous and disordered materials consider the media as system of groups of elementary dipoles (charge carriers in double potential wells), polarization characteristics of which significantly differ from elementary ones. Relaxation time of dipole’s formations may spread in wide temporal or frequency range, even if elementary dipoles are not temporally distributed. The model simultaneously explains fractional power shape of spectra and exponential temperature dependence of dielectric loss according to inverse Arrhenius law exp(T/T_0). According to model frequency exponent n linear decreases with increasing temperature. The frequency dependence of parameter T_0 has been explained and their correlation with other properties of amorphous materials has been analyzed.

E.EP1.43
16:00
Authors : P. Vancsó1, 5, I. Hagymási2,3, Yong-Sung Kim4, 5, Chanyong Hwang4,5, L. Tapasztó1,5 and L. P. Biró1, 5
Affiliations : 1 Institute of Technical Physics and Materials Science, Research Centre for Natural Sciences, PO Box 49, H-1525 Budapest, Hungary, www.nanotechnology.hu 2 Strongly Correlated Systems ”Lendület” Research Group, Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, PO Box 49, H-1525 Budapest, Hungary 3 Department of Theoretical Physics, University of Szeged, Tisza Lajos krt 84-86, H-6720 Szeged, Hungary 4 Center for Nano-characterization, Division of Industrial Metrology, Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Republic of Korea 5 Korean-Hungarian Joint Laboratory for Nanosciences, PO Box 49, H-1525 Budapest, Hungary

Resume : Graphene nanoribbons (GNR) with atomically perfect zigzag edges have a magnetic insulating ground state with antiparallel spin orientation between the two edges [1]. However, in real systems edge reconstructions and defects are always present. Ab-initio calculations have shown that under ambient conditions various edge reconstruction can be realized. One of the most preferable edge reconstruction is the extended pentagon-heptagon (5-7) reconstruction, which has also been recently observed by transmission electron microscopy [2]. In this work we have performed electronic structure and magnetic ordering calculations on GNRs with reconstructed and defective zigzag edges including the (5-7) reconstruction by applying the mean-field theory for the Hubbard model. Within the framework of this approximation we have also investigated the influence of the temperature, carrier density and the width of the GNRs on their electronic and magnetic properties. Our results indicate that these properties significantly depend on the type of the edge reconstruction and the external conditions. These predictions can be verified on GNRs which are fabricated by scanning tunneling lithography [3]. [1] Young-Woo Son, et al., PRL 97(2006) 216803 [2] Kwanpyo Kim, et al., Nat. Commun. 4(2013) 2723 [3] L. Tapasztó, et al., Nature Nanotech. 3(2008) 397-401

E.EP1.54
16:00
Authors : Tamar Tchelidze, Tamaz Kereselidze, Teimuraz Nadareishvili
Affiliations : Ivane Javakhishvili Ybilisi State University, Faculty of Exact and Natural Sciences

Resume : Semiconductor nanowires, are believed to act as key elements in future nanoscaled optoelectronic devices, as they offer intriguing electrical and optoelectronic properties. However, the future of any semiconductor nanowire technology will essentially rely on their doping capability. The availability of both n- and p-type semiconductors is important for the realization of nanowire-based electronics. Wide band gap semiconductors, such as ZnO, suffer from doping polarity. They can be easily by doped n- (or p-type) to the expense of difficulties for doping of opposite type. Space confinement changes donor and acceptor ionization energies; The main factor that makes difficult to obtain n- or p-conductivity is formation of compensating defects. Compensating processes is strongly affected by electronic structure of system: band gap, ionization energies of donors, acceptors and their compensation centers. In the presented work we calculated energy levels of electron bound to Coulomb impurity that is incorporated in semiconductor nanowire. Effect of dielectric confinement on ionization energies are considered as well. For analyzing perspectives of suppressing processes of compensation and achieving high ohmic p-conductivity Kroger method of quasi-chemical equations is used.

E.EP1.55
16:00
Authors : H. Ibadullaeva, A.O. Rahimova, A.P. Mukhtarov, M. Isakulova
Affiliations : H. Ibadullaeva, A.O. Rahimova, National University of Uzbekistan, 100214 Tashkent, Uzbekistan; A.P. Mukhtarov, Institute of Nuclear Physics AN RUz, 100214 Tashkent, Uzbekistan; M. Isakulova, Djizzakh State University, 130100 Djizzakh, Uzbekistan

Resume : Silicon nanoparticles have a great interest as a nanoelectronic materials. Impurities in Si has a big influence to his optoelectronic properties. The most undesireable impurities are carbon and hydrogen atoms. They play a key role in changing optoelectronic parameters of devices drastically changing their in overdoping semiconductor crystals. At the same time these impurities effect to nanoparticles characteristics has not yet been studied completely. We have studied spatial and electronic structure of the Si nanoparticles doped by carbon and hydrogen atoms by computer simulation in the frame of detalized tight-binding method combined with molecular dynamics simulation.

E.EP1.58
16:00
Authors : A.V. Gert, I.N. Yassievich
Affiliations : Ioffe Physical-Technical Institute of the Russian Academy of Sciences

Resume : The experimental data recently obtained by the femtosecond pump-probe spectroscopy technique have shown that the self-trapped exciton (STE) state plays a key role in the dynamics of hot excitons in the photoexcited silicon nanocrystals embedded in SiO2 matrix [W. D. A. M. de Boer, et al., Phys. Rev. B 85, 161409 (2012)]. We present the theoretical model of excitons self-trapped on Si-O bounds at the silicon nanocrystal surface. The capture of hot free excitons at self-trapped states as well as the reverse process have been studied. The nonradiative multiphonon recombination of the STE initiated by interaction with vibrations of local dipoles in amorphous SiO2 matrix has been considered, too [A.V. Gert, I.N. Yassievich, JETP Letters 97, 87 (2013)]. The relaxation process of "hot" carriers localized in Si nanocrystals has been modulated using Monte Carlo method. We demonstrate that effective exchange between the STE states and "hot" free exciton states leads to the wide energy distribution of "hot" carriers during 10-100 pcs after excitation.

E.EP1.59
16:00
Authors : T. Tchelidze, T. Gagnidze, A. Shengelaya
Affiliations : Ivane Javakhishvili Tbilisi State University, Faculty of Exact and Natural Sciences

Resume : multiferroic materials, which simultaneously display magnetic and electric order have attracted interest because of their physical properties very promising for multifunctional device application. Among these properties the magnetoelectric coupling between the electric and magnetic degrees of freedom, where an electric (magnetic) polarization can be induced by a magnetic (electric field), is especially important. Bismuth ferrite (BFO) belongs to a class of single-phase multiferroic materials. This compound has become recently subject of great interests due to room temperature multiferroic properties. A number of experiments have indicated that properties of BiFeO3, such as remnant polarization, dielectric constant, magnetization are very sensitive to defects. The presence of charged defects in ferroelectrics especially influences polarization and conductivity. Charged defects in ferroelectric material often combine into defect dipoles (DDs) or defect (donor-acceptor) complexes. In ferroelectrics the lowest energy configuration is satisfied when DDs align to spontaneous polarization We provide thermodynamic analyses of defect concentrational equilibrium in BFO, by means of Kroger method of quasi-chemical equations. We consider the system BFO (solid)-oxigen (gas) and calculate composition of defects at given temperature in dependence on oxygen partial pressure. Temperature and pressure ranges that coincide p-type, compensated, or n-type samples are defined. It is shown that for creation defect complexes, which strongly affects polarization properties of material, treatment in high oxygen pressure is needed. Calculation are carried out for BFO thin films and nanowires. The effect of reduction of dimensionality on DDs formation is discussed.

E.EP1.62
16:00
Authors : M. Yilmaz2,4, B. Altuntas*1,2, S. Ilday2,3, R. Turan1,2 , S. Cosentino5, R. Raciti5, I. Crupi5, A. Mio5, G. Nicotra5, A. Terrasi5, S. Mirabella5
Affiliations : 1Department of Physics, Middle East Technical University, 06800, Ankara, TURKEY 2Center for Solar Cell Research and Applications (GÜNAM), Middle East Technical University, 06800, Ankara, TURKEY 3Department of Micro and Nanotechnology, Middle East Technical University, 06800, Ankara, TURKEY 4Department of Physics, Necmettin Erbakan University, 42090, Konya, TURKEY 5Dipartimento di Fisica e Astronomia and CNR-INFM, MATIS, Università di Catania, I-95123, Catania, ITALY

Resume : Ge nanocrystals is an attractive material for solar cell application due to quantum size effect, which makes it possible to tune the band gap and optical absorption properties. However, electronic transport between isolated nanocrystals should rely on the tunneling efficiency through the dielectric material in between them. It is highly desirable to have a system having both quantum confinement and easy transport channel. This is possible only in the case of interconnected nanostructures having a confinement in one or two dimensions. In this work we have prepared interconnected, sponge-like Ge nanostructures in SiO2 matrix using co-sputtering technique. We studied the electrical transport through this composite structure using I-V measurements in the vertical and lateral directions. Due to the differences in the vertical and lateral organization of the nanostructures we observed a difference in the carrier conductivity. This is particularly important for solar cells where the vertical transport is more crucial than the lateral transport. The optical response in these films is investigated by UV-VIS Spectroscopy. The results show that the band gap decreases with increasing substrate temperature as expected from the fact that at the size of Ge nanostructures increases with the substrate temperature. Photoresponse measurements, where the cut-off wavelength corresponds to the band gap of the material, confirm the variation of the band gap with increasing Ge size. We have also fabricated heterojunction device on Si substrate and observed a weak photovoltaic effect in the measured device.

E.EP1.63
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09:45
Authors : T. Yamamoto, H. Song, J. Nomoto and H. Makino
Affiliations : Kochi University of Technology

Resume : We have investigated optical properties of heavily Ga-doped ZnO (GZO) polycrystalline films, which can be promising low-loss alternatives to metals at the telecommunication wavelength bands around 1300 nm and 1550 nm for plasmonics. Current plasmonic devices based on metals or metal alloys at the optical frequencies face significant challenges due to losses encountered in the materials. We deposited GZO films on glass substrates (200ºC) with various thicknesses ranging from 100 to 350 nm by ion-plating with dc arc discharge. Hall effect measurement results showed that 105- and 344-nm-thick GZO films have electrical resistivity of 2.5×10-4 Ωcm, carrier concentration of 1.08×1021 cm-3 and Hall mobility of 23 cm2/Vs and electrical resistivity of 1.8×10-4 Ωcm, carrier concentration of 1.23×1021 cm-3 and Hall mobility of 29 cm2/Vs, respectivley. Hall mobility increased with thicknesses up to 344 nm, whereas carrier concentration changed a little. Analysis based on Drude model shows that 105- and 344-nm-thick GZO films exhibited negative real permittivity at wavelenghth of more than 1256 nm and 1198 nm, respectively, which shows that the samples had a plasma frequency higher than the desired frequency of the application. Note that all the GZO films exhibited values of the imaginary part of the dielectric function of less than 0.6 in the range of wavelength smaller than 1500 nm. Those findings prove that the GZO films can be a promising material for the plasmonics.

E.EO4.3
 
Nanooxides II : Eugene Kotomin
10:30
Authors : Yanwen Zhang (1,2), Dilpuneet S. Aidhy (1) , Tamas Varga (3), Sandra Moll (4), Philip D. Edmondson (5), Fereydoon Namavar (6), and William J. Weber (2,1)
Affiliations : (1) Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; (2) Department of Materials Science & Engineering, University of Tennessee, Knoxville, TN 37996, USA; (3) Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99352, USA; (4) TN International / AREVA, 1, rue des Hérons, 78182 Montigny Le Bretonneux, France; (5) Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK; (6) University of Nebraska Medical Center, Omaha, NE 68198, USA

Resume : Nanocrystalline oxides are of high interests for a wide range of applications due to their exceptional size-dependent materials properties, and nanostructured oxides are considered as potential candidates in advanced energy storage and production. Ever increasing energy needs have raised the demands for advanced fuels, and nanostructured oxides are considered as potential candidates with improved performance in advanced nuclear energy systems Understanding defect-induced effects in nanocrystalline oxides is important. Ion beam is an effective approach to tailor size-dependent material properties of oxide-based nanomaterials. Grain growth of nanocrystalline materials is generally thermally activated, but can also be driven by irradiation at much lower temperature. Cubic ceria and zirconia are well known ionic conductors that are also isostructural with urania, plutonia, and thoria-based nuclear fuels. Under ion irradiation, defect production and ionization effect lead to effective modification of interface volume in nanocrystalline ceria and zirconia. Experimental results have shown that both high electronic energy loss and nuclear energy loss lead to disorder and radiation-induced growth of the crystallite size is a function of total energy deposited. Atomistic simulations by adding high levels of disorder in the simulation cell have revealed fast grain boundary (GB) movements due to the present of high-level disorder in the close proximity to GBs, and the results is in good agreement with our the experimental results. The coupling of energy deposition to the electronic and lattice structures should both be taken into consideration when engineering nanostructural materials.

E.EO5.1
11:00
Authors : V. Trepakov1,2, M. Makarova1,3, Z. Potucek1, O. Stupakov1, E. Tereshina1 A. Dejneka1, L. Jastrabik1, and I. Bykov4.
Affiliations : 1Institute of Physics ASCR, 182 21 Prague 8, Czech Republic 2Ioffe Physical-Technical Institute of the RAS, 194 021 St.-Petersburg, Russia 3 NIMS, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 Japan 4 Institute for Problems of Material Science, NASc of Ukraine, Krjijanovskogo 3, 03680 Kiev, Ukraine

Resume : The interest in developing new approaches for fabrication of nanosized ABO3 highly polarizable perovskite-like oxides, establishment of the relationships between synthesis conditions, particles size and properties of these materials are steadily increasing. We report on recent development of high-efficiency methods of synthesis of nanoparticles (5–80 nm) of nominally pure and doped SrTiO3 and KTaO3 quantum paraelectrics, the analysis of their structure and properties evolution at different temperatures, particles size and correlations between their structural and physical properties depending on the concentration of intrinsic and impurity defects. The main attention is paid to: i) the novel approach to the solvothermal synthesis and properties of the perovskite-type KTaO3 crystalline nanoparticles whose properties are turned out to be strongly controlled by magnitude of the solvent dielectric constant; ii) the noticeable lattice constant increasing was found for small SrTiO3 nanoparticles; iii) unusual temperature behavior of the R-line of photoluminescence of the Cr3+ impurity centers was treated as possible manifestation of low-temperature ferroelectric phase transition for the sufficiently small SrTiO3:Cr nanoparticles and iv) successive synthesis characterization and studies (X-ray, SEM, PIXE, Raman scattering, magnetization, EPR) of highly concentrated cubic perovskite-type SrTi1-xMnxO3 nanoparticles (x up to 0.5) revealing polar and magnetic ordering effects.

E.EO5.2
11:15
Authors : M. Arrigoni, D. Gryaznov, E.A. Kotomin, J. Maier
Affiliations : Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1 D-70569, Stuttgart, Germany; Institute of solid state physics, University of Latvia, Riga, Latvia; Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1 D-70569, Stuttgart, Germany; Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1 D-70569, Stuttgart, Germany

Resume : We discuss, how the one-dimensional confinement affects the electronic and energetic properties of point defects (color centers) in perovskite ultrathin films with respect to the bulk phase. Barium zirconate, BaZrO3, has a perovskite structure and serves as one of the constituent materials in electroceramic capacitors used in wireless communications, high temperature proton conductor and substrate for thin film growth. We have considered BaZrO3 as a model for a wide class of ABO3 perovskite-structured materials with partly covalent chemical bonding. Oxygen vacancies are common defects in perovskites responsible for transport properties. In ultrathin films, confinement effects arise due to the spatial restrictions of ionic relaxation around the defect sites, change of phonon spectra and expansion of the electronic wave function beyond the film boundaries. The study has been carried out performing ab initio simulations within the hybrid HF-DFT LCAO theory. Neutral and charged oxygen vacancies were considered in the bulk phase and in ultrathin films, where the defect was placed in the central layer of slabs with a thickness ranging from 3 to 13 crystalline planes along the [001] direction. As terminating layers of the films, both BaO and ZrO2 crystalline planes have been considered. We analyze the confinement effects through changes in the band structure, phonon spectra, electronic density distribution and the formation energies of defects in ultrathin films.

E.EO5.3
11:30
Authors : Al-Moatasem El-Sayed, Matthew Watkins, Alexander Shluger
Affiliations : Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Resume : The mechanisms of electron and hole trapping in SiO2 and the nature of trapping sites are important for our understanding of a wide range of physical phenomena, such as radiation-induced damage and electrical breakdown, and for applications in fiber optics and micro-electronics. Hole trapping in silica has been relatively well understood with models of trapped holes and several hole trapping defects well established. Using classical and ab initio calculations we demonstrate that extra electrons can be also trapped in pure crystalline and amorphous SiO2 (a-SiO2) in deep band gap states. The structure of trapped electron sites in pure a-SiO2 is similar to that of Ge electron centers and so-called [SiO4/Li]0 centers in quartz. Classical potentials were used to generate amorphous silica models and density functional theory to characterize the geometrical and electronic structures of trapped electrons in crystalline and amorphous silica. The calculations demonstrate that an extra electron can be trapped at a Ge impurity in alpha-quartz in six different configurations. An electron in the [SiO4/Li]0 center is trapped on a regular Si ion with the Li ion residing nearby. Extra electrons can trap spontaneously on pre-existing structural precursors in amorphous SiO2. However, the electron self-trapping in quartz requires overcoming a barrier of about 0.57 eV and self-trapped polarons are unstable with respect to the delocalized state. The precursors for electron trapping in amorphous SiO2 comprise wide (>1320) {O--Si--O} angles and elongated Si--O bonds at the tails of corresponding distributions. Using this criterion we estimate the concentration of these electron trapping sites at ~ 4x1019 cm-3.

E.EO5.4
 
Metallic nanostructures : Kai Nordlund
14:00
Authors : H. Wang (1), T. Picot (2), K. Houben (2), S. Bals (3), C. Detavernier (4), S.A. Brown (5), M.J. Van Bael (2), K. Temst (1) and A. Vantomme (1)
Affiliations : (1) Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium (2) Laboratory of Solid State Physics and Magnetism, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium (3) EMAT, Dept. Fysica, Universiteit Antwerpen, Belgium (4) Department of Solid State Sciences, Ghent University, 9000 Gent, Belgium (5) The MacDiarmid Institute for Advanced Materials and Nanotechnology, Dept. of Physics and Astronomy, University of Canterbury, 8140, Christchurch, New Zealand

Resume : Epitaxial Pb nanoparticles (NPs) were synthesized by high-fluence ion implantation in single crystalline Si, Al and Cu, i.e. three matrices in which Pb has a limited solubility. By varying the fluence, implantation temperature or annealing conditions, the NP size (5-20 nm) and size distribution can be tuned. In combination with the selection of the matrix, the NP lattice parameters can be tuned. The melting/solidification of these Pb NPs reveals large superheating and supercooling effects. These thermal hysteresis effects, which drastically depend on the size of the NPs, are due to the (i) epitaxial alignment and (ii) different lattice mismatch between the Pb particles and the matrices, leading to a different pressure on the Pb NPs. Hence, this effect can be used to modify the melting behavior of the embedded Pb NPs. Pb NPs in Al (two superconductors with different critical parameters) exhibit a single superconducting transition with a critical temperature Tc, which increases linearly with the Pb/Al volume ratio. The good agreement with theoretical predictions of the proximity effect in the Cooper limit for strongly coupled superconductors, illustrates that the quality of the Pb/Al interface is excellent, which we attribute to the ion beam synthesis process. In this presentation, we will discuss the intimate interplay between the structural properties of the Pb NPs, e.g. the particle size, the matrix and the interface quality, and their thermal and superconducting response.

E.EO6.1
14:45
Authors : G. Abadias(1), J.J. Colin (1), D. Magnfält (2), A. Michel (1), K. Sarakinos (2), C. Jaouen (2)
Affiliations : 1. Institut P', Dpt. Physique et Mécanique des Matériaux, Université de Poitiers-CNRS, France; 2. IFM-Linköping University, Plasma and Coatings Physics Division, Sweden

Resume : In the course of the past decade substantial progress has been made in understanding stress generation during thin film growth thanks to real-time and in situ diagnostics based on the measurement of the substrate curvature. Different archetypal stress behaviors have been reported based on the adatom mobility of the deposited material [1]. For deposition conditions that entail the use of hyperthermal species, e.g., magnetron sputtering, cathodic arc and ion beam assisted processes, the development of large compressive stresses is generally reported. For refractory metals, the stress level can reach up to several GPa, which can lead to premature failure by buckling at the film/substrate interface. It is well admitted that defect creation during film growth, as a consequence of the ‘atomic peening’ process, contributes to this compressive stress build-up. However, the intrinsic mechanisms of defect incorporation are not yet fully understood, especially for nanoscale thin films, where grain boundaries may play a significant role. The aim of the present work is to provide a comprehensive picture on the origin of defect-induced compressive stress development during sputter-deposition of low-mobility metals by combining situ wafer curvature (MOSS) and ex situ structural characterization (XRD, XRR, AFM, HRTEM). Examples will be given for Mo and Ta films, deposited in a large range of energetic bombardment conditions, by varying the working pressure, bias voltage and ionization degree of sputtered and buffer gas species (using the sputtering-based technique HIPIMS). The role of grain boundaries will be highlighted by growing films on template layers with controlled grain size. A linear dependence of the compressive stress magnitude with the grain boundary density is revealed from MOSS, suggesting preferential insertion of excess atoms at the grain boundary. This grain boundary densification [2] corresponds to a stress state which is predominantly of biaxial type, as confirmed by ex situ XRD. Above a certain energy threshold, which is material-dependent, incorporation of excess atoms in the grain bulk occurs (mostly as self-interstitials), leading to a hydrostatic stress component at the origin of a lattice expansion. The stability of the growth-induced defects is discussed based on the cohesion energy of the material (stable vs. metastable phases) and stress evolution after ion irradiation (up to 1 dpa). [1] G. Abadias, J.J. Colin, A Michel, C. Jaouen, Vacuum 100 (2014) 36 [2] D. Magnfält, G. Abadias, K. Sarakinos, Appl. Phys. Lett. 103 (2013) 051910

E.EO6.3
17:15
Authors : M. Amato (1), S. Ossicini (2) R. Rurali (3)
Affiliations : (1) Institut d’Electronique Fondamentale, UMR8622, CNRS, Université Paris-Sud, 91405 Orsay, France (2) Dipartimento di Scienze e Metodi dell’Ingegneria, Università di Modena e Reggio Emilia, Via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia, Italy (3) Institut de Ciència de Materials de Barcelona (CSIC), Campus de la UAB, 08193 Bellaterra, Spain

Resume : One of the main limits of doping of pure silicon and pure germanium nanowires (Si and Ge NWs) is its inefficiency when the diameter is reduced, as a consequence of surface segregation of impurities, strong quantum confinement and dielectric mismatch [1]. In the case of doping with boron or phosphorus impurities of Si and Ge NWs the impurity state is deep into the band gap and cannot be electrically activated at typical device temperatures. This phenomenon is responsible of several problems about the real applications of these types of materials for electronic devices. Results of our ab-initio DFT calculations on core-shell silicon-germanium NWs [2] (with diameter of 2.4 nm) show how this limit can be easily overcome by opportune doping with boron and phosphorus impurities. In these nanostructures, in fact, the band offset between the two materials causes localization of the valence states on germanium and of conduction states on silicon. As a consequence of this property, with particular doping conditions, a one-dimensional electron (hole) gas at the band edge is created and the carrier density is uniquely controlled by the impurity concentration without no need of thermal activation. Additionally, SiGe core-shell nanowires, providing naturally the separation between the different types of carriers, electron and holes, are ideally suited for photovoltaic applications. [1] M. T. Bjork, et al. Nat. Nanotech. 4, 103 (2008). [2] M. Amato, et al. Nano Letters, 11, 594, (2011).

E.EO7.3
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09:15
Authors : Yu.F. Zhukovskii(1), S. Piskunov(1), O. Lisovskii(1), J. Begens(1) and E.Spohr(2)
Affiliations : (1) Institute of Solid State Physics, University of Latvia, 8 Kengaraga str., LV-1083, Riga, Latvia; (2) Lehrstuhl für theoretische Chemie, Universität Duisburg-Essen, Universitätstr. 2, 45141 Essen, Germany

Resume : Titania and strontium titanate are well-known semiconductors comprehensively studied in materials science, thanks to their widespread technological applications. Doped TiO2 and SrTiO3 nanotubes (NTs) are known to be potentially promising electrodes for visible-light-driven photocatalytic applications. In this study, ab initio calculations have been performed to study the ground state properties of monoperiodic TiO2 and SrTiO3 nanotubes containing extrinsic point defects. The hybrid exchange-correlation functionals B3LYP and B3PW within the framework of density functional theory have been applied for calculations on NTs with the following substitute impurities: C(O), N(O), S(O), and Fe(Ti). The variations in formation energies obtained for these doped nanotubes have allowed us to predict the most stable compositions, irrespective of the changes in growth conditions. The changes in the electronic structure have been analyzed to show the extent of localization of the in-gap states induced by defect. The mid-gap levels positioned inside the band gaps of defective nanotubes make them attractive for numerous applications. Moreover, inspecting the electronic charge isodensity plots, we have concluded that increased covalency in impurity-host interatomic bonds may enhance adsorption properties of defective NTs. According to obtained results, S-doped TiO2 NT and N-doped SrTiO3 NT make these nanotubes to be good candidates for efficient photocatalyst working under daylight irradiation.

E.EO8.2
09:30
Authors : Luigi Stagi, Pier Carlo Ricci,Carlo Maria Carbonaro, Marcello Salis, Alberto Casu, Francesco Delogu, Stefano Enzo
Affiliations : Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy;Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy;Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy;Dipartimento di Fisica, Università degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy; Istituto Italiano di Tecnologia (IIT), via Morego 30, 16163 Genova, Italy;Dipartimento di Ingegneria Meccanica, Chimica, e dei Materiali, Università degli Studi di Cagliari, via Marengo 2, 09123 Cagliari, Italy;Dipartimento di Chimica e Farmacia, Università degli Studi di Sassari, via Vienna 2, 07100 Sassari, Italy

Resume : Titanium dioxide (TiO2) is a strategic material for a very wide range of applications encompassing pigments, nonlinear optics devices, gas sensor and Dye-Sensitized solar cells. Some mixed-phase TiO2 nanoparticles with coexisting polymorph (anatase + rutile, anatase+brookite) exhibit enhanced photoactivity, possibly due to the separation of charge carriers in different phases that suppresses electron−hole recombination. Hence, much research has been performed to elucidate and control the phase transformation between these two phases. Within this framework, achieving a suitable control of the phase transition behavior of nanometer-sized TiO2 materials would represent a significant progress on the way of their full exploitation in different areas of science and engineering. In this work we report visible light induced anatase to rutile structural phase transformation mechanism depending on the surrounding environment and power laser density on the samples. Thermal origin of the process was excluded by in situ Raman measurements that permit the estimation of the local temperature. The mechanism was attributed to surface defects induced by oxygen desorption involving F color centers. The kinetic of desorption process were also studied through intragap excited photoluminescence measurements. Transmission Electron Microscopy images revealed the presence of small polycrystalline aggregates suggesting the coalescence among neighbouring nanoparticles. Finally, a mechanism to promote or inhibit the transformation acting on the concentration and depth of color centers is presented.

E.EO8.3
 
Properties of SiC : Harry Bernas
10:30
Authors : C.-H. Chen (1), Y. Zhang (2,1), M. L. Crespillo (1), S. Shannon (3), M. Ishimaru (4), and W. J. Weber (1,2)
Affiliations : (1) Department of Materials Science & Engineering, University of Tennessee, Knoxville, TN 37996, USA; (2) Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; (3) Nuclear Engineering Dept., North Carolina State University, Raleigh, NC 27695, USA; (4) Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan

Resume : Nano-engineered silicon carbide (NE-SiC) thin films have been grown on Si (100) wafers by low-pressure chemical vapor deposition. These NE-SiC films predominantly exhibit the 3C cubic structure with nanosized columnar grains grown along the [111] direction. A unique feature of these NE-SiC films is the high density of (111) of stacking faults and twins (planar defects) perpendicular to the growth direction that create a nanolayered structure within each grain. The response of the NE-SiC to electron and ion irradiation, as well as helium implantation and subsequent ion irradiation, has been investigated. The results from electron and ion irradiation studies suggest that defect migration is primarily two-dimensional and limited between the planar defects, which increases the resistance of the NE-SiC to irradiation-induced amorphization. Such two dimensional diffusion is supported by density functional theory calculations. The NE-SiC films have also been implanted with helium ions (up to 8000 appm) at 275°C to avoid irradiation-induced amorphization, and no bubble formation is observed. Subsequent irradiation of the helium implanted samples with 9 MeV Au ions at 700°C to 10 dpa revealed preferential bubble growth at grain boundaries, suggesting that helium migration may also be limited by two-dimensional diffusion. The nanolayered structure exhibits surprising stability under irradiation to 10 dpa at 700°C.

E.EO9.1
11:15
Authors : M.F. Beaufort1, M. Vallet1, E. Oliviero2, J.F. Barbot1
Affiliations : 1Institut Pprime, CNRS - Université de Poitiers - ENSMA - UPR 3346, Département Physique et Mécanique des Matériaux, SP2MI, Bd M. et P. Curie - BP 30179, 86962 Futuroscope, Chasseneuil Cedex, France 2CSNSM - IN2P3 - CNRS, Université Paris-Sud, 91405 Orsay Campus France

Resume : In-situ transmission electron microscopy (TEM) investigations were performed in order to follow the evolution of helium bubbles under heavy ion irradiation (Au, 1.5MeV) in 4H-SiC as a function of fluence. 4H-SiC thin foils containing well-characterized bubble populations consisting of a layer of bubbles with a mean radius of 3nm were used. The SiC / He bubble specimens were then observed and irradiated in-situ in a transmission electron microscope at the JANNuS-Orsay facility*. Results indicated that the effects of displacing irradiation (1.5MeV Au ions) resulted in the gradually decrease of the bubble diameter with dose. A 1-D model showed that half of the ejected–He is re-trapped during the displacing irradiation. At high dose, the excess of vacancies due the combined effects of bubble shrinkage and displacing irradiation concomitant with a large concentration of free-He-atoms leads to the formation of satellite tiny-bubbles. The system evolves toward a steady state of bubble size keeping all the helium atoms in the matrix

E.EO9.3
11:30
Authors : A. Debelle1, M. Backman2,4, A. Boulle3, F. Djurabekova4, A. Chartier5, B. Weber2,6, L. Thomé1, K. Nordlund4, F. Garrido1
Affiliations : 1. CSNSM, Univ. Paris-Sud/CNRS/IN2P3, Orsay, France 2. DMSE, University of Tennessee, Knoxville, USA 3. SPCTS, Univ. Limoges/CNRS, Limoges, France 4. University of Helsinki, Helsinki, Finland 5. CEA-Saclay, DEN, DPC, SCCME, Gif-Sur-Yvette, France 6. MST Division, ORNL, Oak Ridge, Tennessee, USA

Resume : Silicon carbide (SiC) has been attracting an increasing interest for many applications in extreme environments such as structural components in fission and fusion reactors or for microelectronics devices. For all these applications, a comprehensive understanding of its behaviour under ion irradiation appears as a major fundamental issue. In this work, we present a combined experimental and computational study of both the amorphization and recrystallization processes that can take place in SiC under ion irradiation. For the amorphization process, 3C-SiC single crystals have been irradiated with 100 keV Fe ions at different fluences and characterized using RBS/C and XRD. Strain and damage levels have been monitored and compared to values obtained from molecular dynamics simulations that simulated controlled, defective SiC cells and a good agreement has been obtained. Furthermore, the well-known stimulation of the amorphization process has been confirmed and was attributed to the elastic energy stored in the defective layer that contains irradiation defects. Regarding the recrystallization phenomenon, damaged 3C-SiC single crystals have been submitted to swift heavy ion irradiation (870 MeV Pb ions) and a healing effect has been evidenced. The recovery has been observed experimentally using RBS/C and TEM and confirmed by MD calculations combined with thermal spike modelling.

E.EO9.4
13:30
Authors : Aziz Zoubir* , Sefir Yamina, Djelti redouan and Bentata Samir
Affiliations : Laboratory of Technology and Properties of solid

Resume : The effect of a uniform electric field across multibarrier systems (GaAs/AlxGa1-xAs) is exhaustively explored by a computational model using exact Airy function formalism and the transfer-matrix technique. In the case of biased DFHBSL structure a strong reduction in transmission properties was observed and the width of the miniband structure linearly decreases with the increase of the applied bias. This is due to the confinement of the states in the miniband structure, which becomes increasingly important (Wannier-Stark effect).

E.EP2.2
13:30
Authors : A. Abbasi Eliyaderani, S. M. Zebarjad, M. Kashefi Torbati
Affiliations : Atefeh Abbasi Eliyaderani' Seyed Mojtaba Zebarjad' Mehrdad Kashefi Torbati

Resume : One of the main limitations in application of Cyanoacrylate (CA) groups is their mechanical properties such as scratch resistance that is not clearly defined. Based on literature survey done by the authors, there are not any papers concentrated on role of nano-size particles on scratch behavior of Cyanoacrylate glue. Thus the main goal of the current research is focused on the role of nano-size SiO2 on scratch behavior of Cyanoacrylate. For this purpose Alkoxyethyl Cyanoacrylate and silicon dioxide nano powders were used as matrix and reinforcement respectively. Para-toluene solfunic acid and caffeine were added to the glue. All samples were scratched under different loads and the scratch velocity was kept constant. The scratch behaviors of Cyanoacrylate nanocomposites were evaluated using scanning electron microscopy. The results indicated that Cyanoacrylate nanocomposites exhibit a more brittle damage mode, which is evidenced by the regular plastic drawing and crack lines. Various scratch induced damage features, such as mar, pseudo fish-scale, parabolic crack, and material removal, observed in the studied nanocomposites. Microscopic evaluation showed that with addition of nano size SiO2, the Cyanoacrylate scratch mechanism changed.

E.EP2.3
13:30
Authors : T. Bentrcia, F. Djeffal, M. Meguellati and D. Arar
Affiliations : 1) Department of Physics, University of Batna,Batna 05000, Algeria. 2)LEA, Department of Electronics, University of Batna, Batna 05000, Algeria. E-mail: faycal.djeffal@univ-batna.dz, faycaldzdz@hotmail.com, Tel/Fax: 0021333805494

Resume : The SiGe-based alloy is considered as one of the most promising materials for reliable and high performance microelectronic devices. The use of a lower band-gap material in the channel region of the MOSFET, such as SiGe, is a potential candidate given their compatibility with the process developed for pure Si-based devices. Moreover, the important increasing in the drain current due to the increased electrons mobility in SiGe material is expected. However, the growth of this material is not totally controlled, and the presence of defects is more than expected after a growth run of this material. Therefore, in order to obtain a global view of SiGe-based nanoscale Double Gate (DG) MOSFET performance under critical conditions, numerical modeling of nanoscale SiGe DG MOSFET including Interfacial defect effects (SiGe/Si) is indispensable for the comprehension of the fundamentals of such device characteristics. Based on numerical investigation of a nanoscale SiGe DG MOSFET including the defects in the interface region, in the present paper a numerical model for I-V and small signal characteristics by including the interfacial defects, after considering the uniform function approximation for the interface defects distribution at the drain said, is developed to explain the immunity behavior of the nanoscale SiGe-based transistor against the defect densities. In this context, DC and RF characteristics of the proposed design are analyzed by 2-D numerical simulation and compared with conventional Si DG MOSFET characteristics.

E.EP2.4
13:30
Authors : N.A.Nurmatov, Y.S.Ergashov
Affiliations : National University of Uzbekistan

Resume : Study the penetration depth of niobium atoms in Mo (110) and (100), the construction of high-quality model of the niobium atoms near the surface of alloy. Using the low-energy ion implantation method of niobium atoms, monocrystalline samples were obtained from the niobium-molybdenum alloys . Concentration distribution of niobium atoms in a depth monocrystalline molybdenum were determined. Change of the atomic concentration on the subsurface of the alloy has been experimentally shown based on the heat treatment and prolonged heating of the crystal. A maximum concentration of niobium atoms is observed at approx. 4 atomic layer depth of the diluted alloy at a temperature close to 1400 K. A maximum atomic concentration of the niobium atoms on the subsurface of the alloy reaches to approx. 3%. Auger - spectra, spectral dependent quantum yield, and energy dependent photoelectron distribution [1] indicate that the obtained alloys are clean. Analyzing the results obtained are the following experimental facts. When a crystal surface is bombarded by ions of the alloying element, occurs a spraying of surface layer atoms of the crystal, atoms of the impurity element and the atoms of the doping component. The last one give a limit on the number of elements implemented into the surface layer of the target. On the other hand, in the process play role the atomic structure of the crystallographic orientation, the atomic ratio of the sizes niobium and molybdenum, and surface coupling ma

E.EP2.9
13:30
Authors : Orlova Ksenia Nikolaevna, Gradoboev Alexandr Vasilievich
Affiliations : National Research Tomsk Polytechnic University

Resume : The results of research of resistance AlGaInP heterostructures with multiple quantum wells to irradiation of 60Co gamma rays are presented. Investigations were performed on the LEDs (λ = 630 nm). Irradiation was performed in the passive mode, i.e. without the application of an electric field, and the level of exposure was characterized by the absorbed dose. It is established that the reduction of the light output power during irradiation by gamma rays occurs in the three stages. At the first stage light output power reduction is a consequence of radiation-induced restructuring initial defects, and the second stage - due to the introduction of radiation defects. In the extreme case, the second stage proceeds to the third stage (the mode of low electron injection). On the boundary between the first and second stages relaxation processes - a partial recovery of the light output power on its overall decline are observed. Heterostructures with a pronounced effect of small doses - restoring light output power due to radiation-induced strain relaxation without the formation of additional structural defects are identified. These process precedes the first stage of light output reduction under irradiation by gamma rays.

E.EP2.10
13:30
Authors : B.E.Umirzakov, S.B.Donaev
Affiliations : Tashkent state technical university

Resume : Works carried out showed in recent years that in case of semiconductor and dielectric films in the course of ionic implantation and the subsequent annealing in blankets is formed two - and three- component nanocrystals and nanofilms. Similar researches for metals and metalfloatables weren't carried out so far. This work is devoted to research of change of topography, structure and properties of a surface of Pd and PdBa (Вa-1,5 of %) at ionic bombing and the subsequent annealing. Technological processing (ionic implantation, a thermal activation) and researches of structure, electronic structure, issue properties, degree of a covering of a surface decided by Ba atoms on use by the AES, EELS and UES methods in the conditions of ultrahigh vacuum (Р ≤ 10-6 Pa). The technique of experiment is described in [1]. The topography of a surface was studied by the SEM method in standard Camabax installation. Bombing carried out Ba+ ions with energy of E0 = 0,5-5 keV and a dose of radiation of D = 1014-1017 cm-2. Since a dose of D = 1015 cm-2 on a surface of Pd were formed separate cluster phases enriched with atoms of barium with superficial diameters to 50-60 nanometers. With increase in a dose to D ≈ 5÷6•1015 cm-2 the sizes of these phases increased and formed islands, and at a dose of D ≥ 1016 cm-2 are formed the continuous uniform alloyed layer. After warming up at T=100-1100 K in all above specified cases connections like Pd-Ba, with thickness from 3-4 nanometers (were formed at E0=0,5 keV) to 10-12 nanometers (E0=5 keV). In work the analysis of the received results is given.

E.EP2.12
13:30
Authors : Antonova L.Kh.1, Demikhov Т.Е.2, Тroitskii A.V.1, Didyk A.Yu.3 , Kobzev A.P.3, Kulikauskas V.S.4, Mikhailova G.N.1
Affiliations : 1 A.M. Prokhorov General Physics Institute of RAS; 2 Lebedev Physical Institute of RAS; 3 Joint Institute for Nuclear Research; 4 Skobeltsyn Institute Nuclear Physics of MSU (Moscow State University)

Resume : Proton irradiation H (2.5 MeV) have been conducted of the 2-G composite HTS (high temperature superconducting) tapes YBCO(123) to increase the current-carrying capacity and determine the radiation resistance. The HTS tapes have complex multilayer architecture, wherein the superconducting layer takes only 1% in the thickness. TRIM Model calculations have shown that the energy of protons should be about 2.5 MeV so that the path length within the tape was more than 20 microns, and protons could achieve the superconductor layer. Irradiation was carried out on the Dubna accelerator (AG-5) and in MSU. The sample temperature did not exceed 100C during the irradiation. Measurements of Tc and Ic were carried out by the resistive method. The dependence of the critical current on the magnetic field studied in fields up to 8T at 77 K. Critical current increasing was observed at the fluence range 2x10^15 - 6x10^15 ions/cm^2. This fact arises from generation of radiation defects in the superconductor during H irradiation. A threshold was defined: 6x10^16 ion/cm^2 for radiation damage of the 2-G YBCO tape. Since protons do not cause tracks in the material, as in the case of heavy-ion irradiation, therefore the generation of pinning centers have to go through the other mechanism.

E.EP2.14
13:30
Authors : Luigi Stagi , Jose A. De Toro, Andrea Ardu, Carla Cannas, Alberto Casu, Pier Carlo Ricci
Affiliations : Dipartimento di Fisica, Universitá degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy;Instituto Regional de Investigación Científica Aplicada (IRICA), Departamento de Física Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain; Department of Chemical and Geological Sciences, University of Cagliari, Monserrato Campus, SS 554 bivio Sestu, I-09042 Monserrato (CA), Italy;Department of Chemical and Geological Sciences, University of Cagliari, Monserrato Campus, SS 554 bivio Sestu, I-09042 Monserrato (CA), Italy; Nanochemistry Department, Istituto Italiano di Tecnologia, via Morego 30, 16163 Genova, Italy;Dipartimento di Fisica, Universitá degli Studi di Cagliari, S.P. Monserrato-Sestu Km 0,700, 09042 Monserrato (CA), Italy

Resume : Iron oxides are characterized by a wide variety of compounds, which differ by structural and magnetic properties. The continuing interest for this kind of materials is mainly due to the ability to take advantage of their diversity to find new important applications in several research field. Among iron oxides, γ-Fe2O3 has attracted a growing attention because its use as catalyst, pigment, gas sensitive material. Its potential applications also concern the realization of high density magnetic storage device and in vivo biological studies. In this work we report the structural evolution of -Fe2O3 (maghemite) in bare nanoparticles and in core/shell -Fe2O3/SiO2 systems as a function of laser irradiation and heat treatment by the combined use of Raman spectroscopy, Transmission Electron Microscopy, X-ray Diffraction. In the bare system,-toα- Fe2O3(hematite) phase transformation was obtained with very low beam density powers (less than 2 mW at 632.8 nm focalised with a conventional 10X microscope objective). Phase transformation cannot be obtained by light irradiation in a -Fe2O3/SiO2 core/shell system, but it can be induced by heat treatment at very high temperature (1100°C). Fe2O3 nanoparticles at high temperature can diffuse inside the silica matrix forming aggregates with the  phase and increased size. The key role of the particle surface is discussed and a physical mechanism for the nucleation of hematite crystallites from the bonding of neighbouring maghemite nanoparticles through hydrate defect states is proposed.

E.EP2.15
13:30
Authors : S.B.Donaev(a), A.K.Tashatov(b), B.E.Umirzakov(a)
Affiliations : a) Tashkent state technical univercity b) Karshi state univercity

Resume : In this work we studied the effect of ion implantation on the surface topography of single-crystal film GaAs. Were obtained electron microscopic image of a GaAs surface after various stages of ion bombardment of Ba+ with energy E0 = 0,5 keV. The surface of the " pure " GaAs has a relatively smooth microtopography. Implantation of barium ions from the dose D=4·1014 cm-2, leads to a change of surface microrelief. At a dose of D=8·1014 cm-2 in the surface region of GaAs appear separate molecular complexes - clusters with modified structure and composition. They arise due to sharp thermal heterogeneity and in some cases reach a diameter of 10-15 nm. Since the dose D=6·1015 cm-2, there is a union of separate sections (clusters) with each other. Increasing the dose of Ba+ ions to 6·1016 cm-2 leads to the complete unification of clusters and surface layers of GaAs completely amorphized. Postimplantation annealing at T=900 K for 30 min causes recrystallization of the surface layer and the formation of ternary compounds such as Ba+Ga+As. In this annealing sample implanted dose D=8·1014 cm-2, results in the formation island film, and annealing the sample implanted with D=6•1016 cm-2, - a continuous film. In both cases, the formed compound with an exemplary ternary composition Ga0.4Ba0.6As.

E.EP2.17
13:30
Authors : S.N.Mustafaeva 1, M.M.Asadov 2
Affiliations : 1Institute of Physics, National Academy of Sciences of Azerbaijan, 2Institute of Chemical Problems, National Academy of Sciences of Azerbaijan

Resume : TlInSe2 single crystals are typical representatives of chain-layered semiconductors and attract a lot of attention due to their interesting physical properties. These properties include strong anisotropy of the electric parameters related to special features in the crystalline structure. Chain and layered crystals usually contain structural defects, such as vacancies and dislocations. The presence of these defects results in a high density of localized states near the Fermi level. The states localized in the band gap are responsible for most electronic processes occurring in semiconductors. The large anisotropy in chemical bonding (strong, ionic-covalent bonds within the chains and weak, van der Waals forces between the chains) enables effective doping of TlInSe2 single crystals. The concentration and nature of dopants have a significant effect on the electrical properties of TlInSe2 single crystals. The electrical properties (loss tangent, real and imaginary parts of complex dielectric permittivity, and ac conductivity of Er-doped (1 mol % Er) p-type TlInSe2 single crystals have been studied in the frequency range from 50 kHz to 35 MHz. The results demonstrate that the dielectric dispersion in the studied crystals has a relaxation nature. The experimental frequency dependence of the dissipation factor for TlInSe2:Er single crystals is characterized with a monotonic descending with frequency, which is evidence of the fact, that conductivity loss becomes the main dielectric loss mechanism at studied frequency range. At all studied frequencies the ac conductivity of the crystals varies according the law, characteristic of hopping conduction through localized states near the Fermi level. The Fermi-level density of states, the spread of their energies, and the mean hop distance and time have been estimated.

E.EP2.21
13:30
Authors : V.V.Andreev1, G.G.Bondarenko2, V.M.Maslovsky3, A.A.Stolyarov1, D.V.Andreev1
Affiliations : 1) Bauman Moscow State Technical University, Kaluga Branch. 4, Bazhenov St., Kaluga, 248600, Russia 2) National Research University Higher School of Economics, 20, Myasnitskaya Ulitsa, Moscow 101000, Russia 3) The state unitary enterprise of a city of Moscow Research-and-production centre "SPURT", Zelenograd, West of the 1-st proezd 4, 124460, Russia

Resume : The effect of high-field injection–thermal and irradiation treatments on MIS structure reliability and decrease defects of the nanothin gate dielectric have been investigated. Injection-thermal treatment (ITT) of MIS structures was the high-field electron injection given the charge in gate dielectric and then the restoration of parameters of MIS structures by means of thermal annealing. MIS structures have been studied using the new techniques of control current stress. The study showed that the ITT can improve the MIS structures reliability, leading to an increase in the charge injected to breakdown and identify structures with defects. This result was attributed to a structural modification of SiO2 and its interfaces as a result of ITT. It is shown that the ITT at elevated temperatures can lead to poor reliability characteristics of MIS devices. This phenomenon seems to be associated with obstruction of the activation of electron and hole traps at elevated temperatures. It has been shown that the irradiation treatment allows to reduce the density of defects in thermal SiO2 films, SiO2 films doped phosphorus and oxynitride films and as a result is increased the reliability of MIS devices.

E.EP2.22
13:30
Authors : S.J.Nimatov, D.S.Rumi
Affiliations : Tashkent state technical university

Resume : The investigation of the initial stage of the epitaxial growth of nanocrustals is needed to get the information on the layer structure and to identify the mechanism of the growth. With the development of the surface sensitive method of low and mean energy electron diffraction and technology tendency to nanofilm systems, the estimations of the degree of the surface perfection at the qualitatively new quasi-two-dimensional level, obtained during the epitaxial growth of real surface are needed. While investigating the ultrafine layers the sensitivity of the diffraction methods to the characteristic manifestations of growth initial stages rises, connected with the growth velocity change. Both the selective deposition with the following island coalescecence and defect annealing on substrate surface and also the development of proper nanofilm defects define the contrast of the structural and hence the electrophysical properties of the transition layers and phase boundaries. An apparatus has been made which allowed to measure the contrast of the diffraction and background intensities of low energy electron diffraction (LEED) patterns and to estimate the structural surface perfection. The initial stage of Bi layer growth on Si(111) and solid-phase epitaxy for Ge on Si(111) have been investigated. The conditions which allow to choose the production processing for atomically smooth Bi surfaces on Si(111) have been determined. The influence of heat treatment conditions for Si(111) sample on the preepitaxial preparation and structure of Ge film during annealing and evaporation stages have been studied.

E.EP2.24
13:30
Authors : B.E.Umirzakov, S.J.Nimatov
Affiliations : Tashkent state technical university

Resume : Ion-electron technology coupled with atomic-sensitive diagnostic methods is widely used in modern thin film nanoelectronics. In recent years there is an increasing interest in the study of thin films of metal silicides and epitaxial films like CoSi2, CaF2 due primarily uniqueness of their physical properties. On the basis of such silicide films the new of multi-layer systems like silicide -insulator-semiconductor can be created, which are the basic elements of highly complex devices of solid state electronics (LSI, ULSI, radiation detectors, solar elements, electronic storage devices etc.). Although these films have the same crystal structure, they must be in agreement with certain requirements: the presence of strong chemical bonds and low diffuse of atoms of contacting surfaces, the proximity of the lattice constants and of the thermal expansion coefficients. The main optical parameters are the refractive index n, the reflection coefficient r, and the dielectric permittivity. All of these parameters are directly connected with the microscopic parameters of the crystal and depend on the temperature and in some cases on the thickness of the dielectric film. In this paper, the chemical composition and the distribution profile of the impurity atoms in depth of nanofilm CoSi2/SaF2 system grown on the Si (111) by molecular beam epitaxy (MBE) method under ultrahigh vacuum conditions have been studied by use of the Auger Electron Spectroscopy (AES) and by Secondary Ion Mass Spectr

E.EP2.25
13:30
Authors : N.A.Balakirev, V.A.Zhikharev
Affiliations : Kazan National Research Technological University

Resume : High dose Fe+ ion implantation into Si assisted by an external magnetic field results in the formation of granular magnetic film with pronounced uniaxial magnetic anisotropy in the film plane[1]. In [2] it was supposed that the anisotropy is caused by the growth of elongated clusters of magnetic silicide Fe3Si and computer simulation of this process was made. Magnetic (ferromagnetic) resonance is one of the methods sensitive both to the shape of ferromagnetic particles and to their spatial arrangement. In the present work, the features of magnetic resonance signals for synthesized Fe3Si films are numerically studied. Shape anisotropy of the clusters leads to large shift of resonance signal depending on the magnetic field orientation. Dipole-dipole interaction between clusters also results in the signal shift, but, more important, strongly influences the absorption line shape (for example, at 10% concentration of clusters in the film the absorption line is bimodal). The results are due to the peculiarities of dipole field distribution over the granular film which are discussed. [1] G.G.Gumarov,V.Yu.Petukhov,V.A.Zhikharev et al. Nucl.Instr.Meth.Phys.Res.B, 267 (2009) 1600 [2] N.A.Balakirev,G.G.Gumarov,V.A.Zhikharev et al. Comp.Material Science, 50 (2011) 2925

E.EP2.27
13:30
Authors : V.V. Uglov1, G. Abadias2, S.N. Dub3, G. N. Tolmachova4, S.V. Zlotski1, I.A. Saladukhin1, S.S. Leshkevich1
Affiliations : 1Belarusian State University, Minsk, Belarus; 2University of Poitiers, Poitiers, France; 3Institute for Superhard Materials NAS, Kiev, Ukraine; 4Kharkov Institute of Physics and Technology, Kharkov, Ukraine

Resume : Structure and phase composition of the coatings based on transition metal nitrides can be signifi-cantly improved by addition of silicon. Such thin films are potential candidates for radiation-tolerant materials due to high density of interfaces which act as efficient sinks and recombination sites for radiation-induced point defects. The effects of the irradiation (180 keV Xe2+, doses 1•10^16 сm-2 and 5•10^16 сm-2) on the structure, phase composition and hardness of nanocomposite (TiZr)1-xSixN thin (300 nm) films deposited by magnetron sputtering (silicon concentration x≤0.22) were studied. It was found that the increase in Si content results in the transformation of structure from nanocrystalline (x ≤ 0.06, grain size of 10-18 nm) to nanocomposite (0.09 ≤ x ≤ 0.13, grain size of 4-8 nm) and then to amorphous (x ≤ 0.22) state. The phase composition of the films changes from two-phase (crystalline c-TiZr(Si)N + amorphous a-SiNy) to the amorphous system: a-TiZrSiN. Nanocomposite TiZrSN film is a composite based on c-TiZr(Si)N grains with the size of 4-8 nm surrounded by an amorphous a-SiNy phase. Ion irradiation with Xe ions triggers the crystallization of TiZrN-rich grains for nanocomposite (0.09 ≤ x ≤ 0.13) and amorphous films (x≤0.22). It was found that irradiation leads to a decrease in nanoindentation hardness, due to the accumulation of Xe ion in the coating, as well as the elemental redistribution of solid solution constituents in the area of collisions cascades.

E.EP2.33
13:30
Authors : Red’ko R.A., Konakova R.V., Milenin V.V., Shvalagin V.V., Red’ko S.M.
Affiliations : V. Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine, 41 Nauky Pr., 03028 Kyiv, Ukraine

Resume : Epitaxial layers of GaN under investigation were MOCVD-grown on Al2O3 substrate and doped with Si up to 1.6·1019 сm-3 carriers concentration. The width of films was 2.0-2.5 μm varied. Photoluminescence measurements were carried out at room temperature in the 350–650 nm wavelength range using a Perkin-Elmer LS55 PL spectrometer. The spectral dependencies of the optical density of epitaxial structures were measured at 300 K with a spectrophotometer Specord 210 in the 350–1100 nm wavelength range. The treatment in pulse weak magnetic field was at regime with B = 60 mT, f = 10 Hz, τ = 1.2 ms, t=1, 3, 5 and 8 min. All measurements were repeated during the time that was needed to reaching some equilibrium state with non-changed OD and PL spectra. Usually, it was near the month. WMF treatment with different duration leads to different features in OD spectra. The influence of WMF on GaN/Al2O3 device structures leads to the reduction of defects, which exist at the interface film-substrate due to destruction of the metastable complexes. The study of the evolutionary features of GaN/Al2O3 structures OD spectra have shown an exponential dependence of the maximum of WMF-induced effect on the duration of magnetic-field treatment. Such WMF action can be used as a cost-effective method for modification of the structural parameters and decrease of non-equilibrium centres in semiconductor materials and devices

E.EP2.35
13:30
Authors : M. Fialho a, K. Lorenz a, S. Magalhães a, J. Rodrigues b, A. J. Neves b, T. Monteiro b, E. Alves a
Affiliations : a Campus Tecnológico e Nuclear, IPFN, Instituto Superior Técnico, Universidade de Lisboa, EN10, 2695-066 Bobadela LRS , Portugal; b Departamento de Física e i3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal

Resume : Light emission from rare earth (RE) doped III-N semiconductors presents great promise for applications in electroluminescence devices. RE exhibit sharp optical emission lines due to the intra-4fn shell transitions making the tuning of light emission from the ultraviolet to the infrared in the AlGaN host realized by an appropriated choice of the dopant ion. This work study AlxGa1-xN samples grown by halide vapour phase epitaxy on (0001) sapphire substrate. Ion implantation was performed with RE ions emitting in the red (Pr3+), blue (Tm3+) and green (Tb3+) region of the wavelength spectrum. The fluences range between 1x1014 at/cm2 and 1x1015 ion/cm2 and the implantations were performed with the beam tilted (10º) or aligned with the c-axis. Two energies, 150 and 300 keV, were selected to investigate the surface effects. The damage accumulation and the RE lattice site location was investigated by Rutherford Backscattering/Channeling Spectrometry (RBS/C) and High Resolution X-ray Diffraction. Rapid Thermal Annealing treatments at 1200 ºC were performed to remove damage and promote optical activation of the rare earth ions. Results show that RE ions occupy two preferential sites, the high symmetry substitutional Ga/Al site and a site displaced along the c-axis from this regular site. In order to establish models for the observed recombination centres, temperature and excitation intensity dependent Photoluminescence measurements were performed for selected samples.

E.EP2.36
13:30
Authors : Gradoboev Alexander Vasilievich, Sednev Vyacheslav Vladimirovich
Affiliations : National Research Tomsk Polytechnic University

Resume : Radiation influence leads to the degradation of the parameters of semiconductor structures and various manufactured on their basis semiconductor devices. Purpose is researching of "memory effect" under irradiation by fast neutrons in AlGaAs heterostructures. Objects of study - LEDs infrared range based on double heterostructures AlGaAs. Previously we irradiated the LEDs by fast neutrons and performed annealing of radiation defects in the current mode workout. Then radiation power reduction was studied under irradiation by fast neutrons. A result of researches the existence of "memory effect" established. The appearance of "memory effect" leads to an increase in radiation resistance under subsequent irradiation. The possible mechanisms of "memory effect"are considered.

E.EP2.38
13:30
Authors : E.V. Savchenko1*, I.V. Khyzhniy1, S.A. Uyutnov1, G.B. Gumenchuk2, A.N. Ponomaryov3, V.E. Bondybey2
Affiliations : 1Institute for Low Temperature Physics and Engineering NASU, 61103 Kharkov, Ukraine 2Lehrstuhl für Physikalische Chemie II TUM, 85747 Garching, Germany 3Helmholtz Zentrum Dresden-Rossendorf, Dresden 01328, Germany

Resume : Radiation effects in solid N2 attract much attention in diverse fields such as material and surface sciences, physics and chemistry of interstellar and solar systems, particle physics. Radiation-induced phenomena were discussed principally in terms of neutral species reactions. The experiments [1] revealed thermally stimulated exoelectron emission (TSEE) from pre-irradiated N2 films. Creation of ionic species N3+ in electron-bombarded solid N2 was reported recently [2]. Charged defect creation and defect-induced effects in electron-bombarded films of solid N2 were studied employing cathodoluminescence (CL), nonstationary luminescence NsL and activation spectroscopy. Recording the CL spectra sequences on exposure time enabled us to monitor defect production, excited particle ejection and fragmentation of molecules. Surface- and bulk-related species were discriminated by varying electron energy, i.e. the penetration depth. Creation and accumulation of N3+, N4+ and trapped electrons (up to 10^15 cm-3) as well as N radicals was detected especially in the nanostructured films. Spectroscopic evidence of excited N2* (C3Πu) molecule desorption was obtained for the first time. Charge recombination reaction N4+ + e → N2 + N2* → N2 + N2 + hν) is supposed to be the stimulating factor for desorption observed. Dynamics of post-irradiation processes was probed with TSL and TSEE. Comparative study of the NsL with dynamics of the TSL spectra and the TSEE yield elucidated the contribution of neutralization and recombination reactions. [1] I. Khyzhniy, E. Savchenko, S. Uyutnov, G. Gumenchuk, A. Ponomaryov, V. Bondybey, Radiation Measurements, 45 (2010) 353. [2] Y-J. Wu, H-F. Chen, S-J. Chuang, T-P. Huang, Astrophys. J. 768: 83 (2013).

E.EP2.40
13:30
Authors : P.I. Gaiduk, A.Nylandsted Larsen,F.L. Bregolin, W. Skorupa
Affiliations : Department of Physics and Astronomy/iNANO, Aarhus University, Denmark; Department of Semiconductor Materials, Helmholtz-Zentrum Dresden-Rossendorf

Resume : We will report on carbon segregation and precipitation, and on structural transformations in strained layered Si/SiGe/Si and Si/SiSn/Si structures after molecular-beam epitaxial (MBE) growth, carbon ion implantation, and thermal treatment. The idea behind this study is that due to their specific strain distribution, pseudomorphic layers of Si/SiGe and Si/SiSn promote spatial separation of vacancies and interstitials followed by segregation of foreign dopant atoms. Both radiation damage and strain are supposed to have impact on the precipitation of poorly soluble dopants. Based on SIMS data we will demonstrate that the redistribution of the implanted carbon atoms around the strained Si/SiGe layers results in their accumulation on the Si side and depletion on the SiGe side. On the contrary, uphill (ascending) diffusion of carbon into the SiSn layer takes place in the case of the Si/SiSn structure. The TEM study demonstrates formation of plate-like defects, stacking faults and thin carbon-precipitated flakes in the Si/SiGe layers. Raman spectra reveal peaks at 1600 and 2700 cm-1 which might be associated with carbon-related phases, and graphene-like nanoflakes. No such defects are found in the Si/SiSn layers; instead, a very strong effect of retardation of tin precipitation is seen. The concepts of strain-enhanced separation of point defects and dopant precipitation will be discussed.

E.EP2.42
13:30
Authors : Roger A. De Souza
Affiliations : Institute of Physical Chemistry, RWTH Aachen University and JARA-FIT, Landoltweg 2, 52056 Aachen, Germany

Resume : 18O/16O exchange annealing and subsequent Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) analysis is used to investigate oxygen transport in dense, nanocrystalline (average grain size d ≈ 300 nm) ceramics of nominally un-doped BaTiO3. All isotope profiles show the same unusual shape: a flattened profile over the first ~100 nm, followed by a short, conventional diffusion profile. We demonstrate that the entire isotope profile can be described quantitatively by a numerical solution to the diffusion equation based on an increase in the local oxygen diffusion coefficient close to the surface. This position-dependent increase is attributed to additional oxygen vacancies that are generated by diffusion of chlorine impurities out of the ceramics. The presence of chlorine derives from the chemical route necessary to produce nanometric powders: it thus indicates a new manner in which nanocrystalline ceramics may differ from their microcrystalline counterparts.

E.EP2.48
13:30
Authors : A.I. Siahlo 1), N.A. Poklonski 1), S.B. Lastovskii 2), H. Presting 3), N.A. Sobolev 4,5)
Affiliations : 1) Belarusian State University, 220030 Minsk, Belarus; 2) Scientific-Practical Materials Research Centre, NAS of Belarus, 220072 Minsk, Belarus; 3) Daimler Research & Development Ulm, 89081 Ulm, Germany; 4) Departamento de Física and I3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal 5) National University of Science and Technology "MISiS", 119049 Moscow, Russia

Resume : We studied the influence of 3–4 MeV electron irradiation on the electrical properties of p-n junctions formed inside Si_6/Ge_4 superlattices (SL; The lower indices are the numbers of the Si and Ge monolayers in a SL period). I-V characteristics, C-V profiles and admittance were measured at T = 4.2–300 K. At 300 K, the forward branch of the I-V characteristics (IVC) monotonously shifts with increasing electron fluence, Φ, to lower voltages. On the contrary, at 77 K it shifts to higher voltages. At Ф ≥ 1.5*10^17 cm 2, negative differential conductivity (S-type IVC) is observed. Charge carrier and compensating impurity concentration profiles were calculated from the C-V measurements. The charge carrier concentration monotonously decreases with increasing electron fluence in all sample layers. Its relative change is equal in the SL and buffer. The barrier capacitance and conductance of the structures monotonously decrease with increasing fluence at 4.2–300 K as a consequence of the charge carrier removal in both SL and buffer. Admittance measurements at f = 1 MHz show a steep decrease of the capacitance C in the as-grown sample below 30 K, accompanied by a peak in the G(T) dependence. Upon irradiation, the peak shifts to higher temperatures. From these measurements we obtained the activation energy of the level, whose recharging produces the observed behaviour, to be equal to 44 meV. Most probably it belongs to Sb that was used as a surfactant during the sample growth.

E.EP2.49
13:30
Authors : N.A. Sobolev 1), B. Breeger 2), H.T. Grahn 3), W. Wesch 2), E. Wendler 2)
Affiliations : 1) Departamento de F?sica and I3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal; 2) Institut f?r Festk?rperphysik, Friedrich-Schiller-Universit?t, 07743 Jena, Germany; 3) Paul-Drude-Institut f?r Festk?rperelektronik, 10117 Berlin, Germany

Resume : AlAs/GaAs symmetric superlattices (SLs) with periods of 2.8, 20 and 150 nm grown on SI-GaAs(001) substrates were implanted with 200 keV Ar ions at 20 K with fluences in the range from 1*10^12 to 5*10^15 cm?2. The whole damage profile was placed inside the SL. Defect production was studied in situ by means of Rutherford backscattering/channeling (RBS/C) spectrometry and after warm-up to 300 K by RBS/C and cross-sectional transmission electron microscopy (XTEM). The results were compared to those obtained on a series of Al(x)Ga(1-x)As alloy samples with x ranging from 0 to 1. With respect to the amount of damage, the thinnest-period SL behaved like an alloy of the corresponding composition, whereas the behavior of that with a period of 20 nm was already quite peculiar with no coherent amorphization of the different layers. Finally, for the AlAs/GaAs SL with a period of 150 nm, a selective damage and amorphization behaviour was clearly visible in the RBS spectra. A strong defect annealing occurred following a warm-up to 300 K, whereupon the damage profile became narrower. We found a strong dependence of the recovery on the damage level produced during the low-temperature irradiation. The amorphization mechanism of the SLs and its relation to the compositional intermixing, defect diffusion etc. are discussed from the viewpoint of the current models for amorphization in the (Al,Ga)As system.

E.EP2.50
13:30
Authors : N.M. Santos 1), N.A. Sobolev 1), J.P. Leitão 1), M.C. Carmo 1), D. Fuster 2), L. González 2), Y. González 2), W. Wesch 3)
Affiliations : 1) Departamento de Física & I3N, Universidade de Aveiro, 3810-193 Aveiro, Portugal; 2) IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), 28760 Tres Cantos, Madrid, Spain; 3) Institut für Festkörperphysik, Friedrich-Schiller Universität, 07743 Jena, Germany

Resume : The photoluminescence (PL) of InAs/InP quantum wires (QWRs) is observed between 1300–1550 nm, an important region for the optoelectronic industry. The resistance of optoelectronic devices to particle irradiation is crucial in space-based telecommunication applications. In this work, we report on the influence of 2.4 MeV proton irradiation on the PL of self-assembled InAs/InP QWRs and InAs/InP quantum wells (QWs) that show PL emission at similar wavelengths. The PL spectra of the QWRs consist of three main bands corresponding to families of QWRs of different height. The study of the temperature dependence of the PL reveals several excitation and transport processes of charge carriers between the wires of different heights. The proton irradiation leads to a quenching of the PL intensity both in QWR and QW samples. At the highest proton fluence used (1*10^15 cm–2) the intensity is reduced by somewhat more than an order of magnitude. This fact proves an extremely high radiation hardness of the InAs/InP QWRs because the PL in quantum size structures of other materials systems is completely quenched at such a high dose. The thermal stability of the PL is deteriorated upon irradiation, obviously due to the competition for the capture of photoexcited carriers between the QWRs and irradiation-induced defects. Another possible mechanism is tunnel escape of the captured carriers from the QWRs to neighboring defects.

E.EP2.51
13:30
Authors : A.I. Popov (1,2), L. Shirmane (1), V. Pankratov (1), A. Lushchik (3), V.E. Serga (4), A. Kotlov (5), J. Zimmermann (6)
Affiliations : (1) Institute of Solid State Physics, Univ of Latvia, Riga, LV-1063, Latvia; (2) Institute Laue-Langevin, F-38042 Grenoble, France; (3) Institute of Physics, Univ of Tartu, Tartu, 51014, Estonia; (4) Riga Tech Univ, Inst Inorganic Chemistry, LV-2169 Salaspils, Latvia; (5) HASYLAB, DESY, Hamburg, D-22761, Germany; (6) TU Darmstadt, D-64287 Darmstadt, Germany;

Resume : Comparative analysis of the luminescent properties of nanocrystalline MgO with macrocrystalline powder analogues and a single crystal has been performed under excitation by pulsed VUV synchrotron radiation. Special attention was paid to VUV spectral range, which is not reachable with commonly used lamp and laser sources. The nanopowder with average crystallite size of nanoparticles (10-15 nm) of MgO was prepared by the extractive-pyrolytic method, while single crystal of MgO was grown by the arc-fusion method. Luminescence spectra and the excitation spectra for different emissions have been studied at the Superlumi station of HASYLAB at DESY using synchrotron radiation of 3.6-25 eV from the DORIS III storage ring in a wide temperature range of 10-293 K. Results obtained show clearly a distinct difference in the excitation spectra for nano- and macrocrystalline samples. A considerable blue shift of about 0.3 eV of the luminescence excitation band caused by deformation-induced defects/vacancy complexes is revealed in nanocrystalline samples.

E.EP2.54
13:30
Authors : N. Korsunska1, V. Papusha1, O. Kolomys1, V. Strelchuk1, A. Kuchuk1, V. Kladko1, Yu. Bacherikov1, T. Konstantinova2, L. Khomenkova1
Affiliations : 1) V. Lashkaryov Institute of Semiconductor Physics, 45 Pr. Nauky, Kyiv 03028, Ukraine 2) Donetsk Institute for Physics and Engineering named after O.O. Galkin of the NASU, 72 R. Luxemburg str., Donetsk 83114, Ukraine

Resume : ZrO2 offers diverse applications such as catalysts, high temperature and corrosion resistant coatings, sensors, radiation detectors, etc. Present work deals with the study of luminescence and structural properties of Y2O3-ZrO2 nanopowders with different Y2O3 content. The powders were sintered by co-precipitation of Zr and Y nitrates at different calcination temperatures. The structural and light emitting properties were controlled by XRD, TEM and Raman scattering, photo- (PL) and cathodoluminescence (CL) methods. At the same calcinations temperature, the increase of Y2O3 content stimulates the decrease of the sizes of ZrO2 nanograins and the transformation of crystalline phase from monoclinic through the tetragonal to cubic. Generally, room temperature PL spectra showed several bands in UV-orange range, whose shape depends on the excitation light wavelength. Along with this, CL spectra demonstrate additional “red” emission, which intensity exceeds that of other CL bands. At lower temperatures, preferable enhancement of “red” CL band, its narrowing and peak position shift to the longer wavelengths were found. This behaviour testifies to the non-elementary nature of “red” CL band. Its nature and mechanism of its excitation are discussed. It is supposed that complex defects, containing oxygen vacancies and impurities, are responsible for this emission appeared under high-energy excitation only. The dominant contribution of red emission into CL spectra opens some perspectives for its application as a marker for high-energy radiation.

E.EP2.55
13:30
Authors : O.M.Sydor, Z.D.Kovalyuk
Affiliations : Chernivtsi Department of the Institute of Materials Science Problems, the National Academy of Sciences of Ukraine, Iryna Vilde St., 5, Chernivtsi, 58001, Ukraine

Resume : Layered A3B6 crystals, in particular InSe and GaSe, have unique physical properties. So, their cleaved surface (0001) is atomically perfect and also inert in environment. Therefore, InSe and GaSe can be used for creation and investigation of nanosized objects, including high-energy irradiations. In this work, the effect of bremsstrahlung neutron irradiation (Eeff=8 MeV) on surface changes in A3B6 crystals is investigated by AFM method. The used fluences are: F1=10^13, F2=10^14 and F3=10^15 n/cm^2. For initial InSe and GaSe surfaces the roughness average (Ra) was about of 0.053 and 0.059 nm, respectively, and the maximum height difference of the relief did not exceed 0.36 and 0.56 nm, respectively. The formations on the surface of irradiated crystals are, in fact, vacancies which have a form of wells or pits. Their planar distribution is comparatively homogeneous. For GaSe the Ra value increased to 0.83 and 1.29 nm at fluences F1 and F3, respectively, the density of nanoformations (NF) decreased from ~6x10^9 cm^-2 to 2x10^9 cm^-2. Their vertical dimensions did not exceed 1 nm for the fluence F1, but increased by 2–3 times for F3. In the case of InSe, at fluence F1 density of NF was ~2x10^8 cm^-2 and their vertical dimensions did not exceed 2 nm but at fluence F3 these values became ~4x10^7 cm^-2 and ~10 nm, respectively. Note that for the sample subjected to the maximum irradiation the broadening of separate pits and their coalescence into clusters of a bigger size take place.

E.EP2.57
13:30
Authors : N. Gordillo 1, E. Tejado 2, M. Panizo-Laiz 1, J. Y. Pastor 2, J. M. Perlado 1, and R. Gonzalez-Arrabal 1
Affiliations : 1 Instituto de Fusión Nuclear, ETSI de Industriales, Universidad Politécnica de Madrid, C/ José Gutierrez Abascal, 2, E-28006 Madrid, Spain; 2 Department of Materials Science- Research Centre on Safety and Durability of Structures and Materials (CISDEM) , UPM-CSIC, C/ Profesor Aranguren s/n,E- 28040, Madrid, Spain

Resume : Owing to its properties: high melting point, low vapor pressure, low physical and chemical sputtering yields, low thermal expansion, electrical conductive properties and relative chemical inertness, tungsten seems to be one of the best candidates to be used as shielding material in plasma facing materials (PFM) for future nuclear fusion reactors. Nowadays, the capabilities of nanostructured materials for such applications are being attracted much attention due to their radiation-resistant and self-healing behavior. In this work, the capacity of the nanostructured W (nW) as protective role in PFM is studied and the radiation-induced changes in the structure and mechanical properties have been investigated. For this purpose, high density coatings made of nanometric tungsten columns (nW) were prepared by direct current (DC) magnetron sputtering and later were implanted under different conditions: (i) single implanted with H, (ii) sequentially with C and H, and (iii) simultaneously (co-implanted) with C and H at room temperature. The stress state was analyzed by X-ray diffraction, while the mechanical properties and adhesion to the substrate have been characterized using the nanoindentation and the nanoscratch techniques respectively.

E.EP2.60
13:30
Authors : Avaz Ruzibaev, Flyura Djurabekova
Affiliations : Department of Physics and Helsinki Institute of Physics, University of Physics

Resume : In many modern applications which employ electric fields of significant strength, such as the Atom Probe Tomography (APT) technique, a successor of field ion microscopy (FIM), or more technological applications such as particle accelerators and vacuum interrupters, it is of great importance to understand the response of surface defects on the field. How strongly atoms on a metal surface or on a semiconductor surface are charged in response to strong electric fields and what is the difference in the mechanisms of surface charge formation can help to understand the atomic behavior in the presence of strong electric fields. We perform electronic structure calculations to study rough features on the Si (100) surface under the influence of external electric field. Charge-transfer dynamics is followed by applying the SIESTA code. Further we use Mulliken and Bader charge analysis tools to estimate the charge excess and depletion on the defects and in their close vicinity. Furthermore, we compare the data obtained for Si surface structural defects with the same defect obtained for metallic electronic structures in the rough Cu surface simulations.

E.EP2.61
13:30
Authors : V. Chornii, S. Nedilko, Yu. Hizhnyi, T. Nikolaenko, M. Slobodyanik, O. Gomenyuk(1), V. Sheludko (1)
Affiliations : Taras Shevchenko National University of Kyiv, 64, Volodymyrs’ka str., 01601 Kyiv, Ukraine (1) Oleksandr Dovzhenko Hlukhiv National Pedagogical University, 24 Kyjevo-Moskovs’ka st., 41400, Glukhiv, Ukraine

Resume : The cadmium molybdate CdMoO4 are well-known scintillation and phosphor materials currently used in various technological applications. Doping of CdMoO4 with F impurities can be done in wide range of dopant concentrations, from several thousands of ppm to synthesis of anion-substituted material CdMoO3F2. Such doping leads to definite changes in optical, in particular, luminescence properties of cadmium molybdate hosts. In this work, the sequence of cadmium molybdate compounds with various F content is considered in theoretical calculations of the electronic structure. The electronic structures are calculated by the Full-potential Linear Augmented Plane Wave (FLAPW) method realized in Wien2k program package [1]. Perfect CdMoO4, fluorine-doped CdMoO4:F in which the oxygen-to-fluorine ratio ranges from 16:1 to 4:1 as well as perfect CdMoO3F2 crystals are treated in geometry-optimized calculations. Structures of the one-electron bands, spatial distributions of the electron densities, optical absorption and reflection spectra are calculated and analyzed. Obtained results are compared with available experimental data of luminescence and optical spectroscopy of pure and fluorine-doped cadmium molybdate crystals. [1] P. Blaha, et. al., 2001, ISBN 3-9501031-1-2.

E.EP2.63
13:30
Authors : Tomasz Zientarski-1, Dariusz Chocyk-2
Affiliations : 1Department for the Modelling of Physico-Chemical Processes, Maria Curie-Sklodowska University, ul. Gliniana 33, 20-614 Lublin, Poland, email: martom@dyzio.umcs.lublin.pl 2Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin, Poland, email: d.chocyk@pollub.pl

Resume : Many important properties of polycrystalline materials are strongly influenced by grain boundaries. High purity metals are polycrystalline materials and they are usually used for fundamental research and for commercially pure materials in modern applications. It is widely known that the structure of grain boundary in these materials influence their mechanical and physical properties. Therefore, the knowledge about the grain boundary effect is very important to understand properties of this systems. To investigate the grain boundary size effect on thin film mechanical properties, we modeled a system with grain boundaries. For simplified polycrystalline geometries, we propose model mimics films intersected by the grain boundaries. To simplify calculation, in our model, we use the grain of rectangular shape. The interactions between metal atoms are described by embedded atom method. The simulation was performed for three-dimensional systems with x-y periodic boundary conditions at a several size of grain boundaries. The grain boundary size was also changed. Simulations show that depending on the size of grain boundaries and a mismatch of the lattice constant in grain and in boundaries leads to various evolution of stress. We applied the kinematical scattering theory for the structural characterization of crystal structures and atomic stress method to analyze simulation data. Relation between stress and diffusion for different size of grain boundaries will be discussed in detail.

E.EP2.66
13:30
Authors : A. Defresne, O. Plantevin, I. P. Sobkowicz, Pere Roca i Cabarrocas
Affiliations : CSNSM, Univ Paris-Sud, CNRS/IN2P3, Orsay, France; CSNSM, Univ Paris-Sud, CNRS/IN2P3, Orsay, France; LPICM-CNRS, Ecole Polytechnique, 91128 Palaiseau, France; LPICM-CNRS, Ecole Polytechnique, 91128 Palaiseau, France

Resume : a-Si:H/c-Si heterojunction solar cells have reached record efficiencies of 24.7%. They consist of a n-type crystalline silicon wafer on which a thin (~10 nm) p-type hydrogenated amorphous silicon (a-Si:H) layer is deposited by plasma enhanced CVD at low temperature (~200 °C). The electrical contact is usually achieved by sputtering a thin transparent conducting oxide (80 nm thick) on the cell. Both sputtering and plasma deposition processes may introduce defects at the c-Si/a-Si:H interface which in turn will determine the conversion efficiency of the cell. The goal of this study is to understand the fundamental aspects of this interface via defect formation using a controlled introduction of point defects. Ion implantation of Argon at low energy (1 to 20 KeV) allows the modification of the a-Si:H thin layer. We can control the depth and concentration of irradiation defects by varying the ion energy and fluence. The defect concentration maximum is adjusted at a depth between 4 nm and 20 nm, while defect concentration is changed over 4 orders of magnitude between 1010 cm-2 and 1013 cm-2. The changes in the effective lifetime of minority carriers upon defect creation or annealing are characterized via photoconductance and photoluminescence measurements. The role of hydrogen diffusion within the amorphous silicon layer under low energy ion irradiation and thermal annealing is tentatively proposed as the origin of the heterojunction interface modification and correlated to the solar cell characteristics.

E.EP2.67
13:30
Authors : L. Lisitsyna, V. Lisitsyn
Affiliations : Tomsk State University of Architecture and Building, sq. Soljianajia 2, Tomsk, 634003 Russia; National Research Tomsk Polytechnic University, av.Lenina 30, Tomsk, 634050 Russia

Resume : The results obtained in the study of LiF crystals doped with oxides of different polyvalent metals (Li, W, Fe or Ti) allow us to conclude that the growth of crystals is accompanied by the self-organization of defects with the formation of nano-sized regions which, in addition to polyvalent metal ion(s), contain oxygen in different states (O2–, OH–, O2) and intrinsic lattice defects. The length of such nano defect reaches at least five interionic distances. Hence the cross section of the capture of electronic excitations by nano defects can be 100–1000 times greater than that by point defects. This means that the nano defects are sinks of electronic excitations, while in undopped crystals electronic excitations are uniformly distributed in the crystal volume. It is found that nano defects having their own spatial and energy structure determine both type and the parameters of radiation-induced processes. So it is established that in doped LiF crystals: (i) dose dependences of F2 color centers accumulation has character different from that in undoped crystals; (ii) in the absorbed doses less than 104 Gy electron pulse repetition rate does not affect the efficiency of F2 centers creating, whereas in the non-activated crystals such a dependence is observed. Assumed that in bulk of the nano defects main mechanism of creating of F2 color centers is correlation mechanism based on the decay of an exciton into a Frenkel pair in the region of the generated F color center.

E.EP2.69
13:30
Authors : Dariusz Chocyk 1, Tomasz Zientarski 2,
Affiliations : 1Department of Applied Physics, Lublin University of Technology, ul. Nadbystrzycka 38, 20-618 Lublin, Poland; email: d.chocyk@pollub.pl 2Department for the Modelling of Physico-Chemical Processes, Maria Curie-Sklodowska University, ul. Gliniana 33, 20-614 Lublin, Poland; email: martom@dyzio.umcs.lublin.pl,

Resume : Mechanical and physical properties of materials in nanoscale are frequently dependent on grain boundaries. Grain boundaries play also an important role in stress generation during growth. In many proposed growth models sources of stress in late stages are connected with mass transport along the boundaries. Therefore, a detailed knowledge about mechanism of diffusion through the grain boundaries is very important to understand properties of this systems. Numerical simulations method are commonly used to study the diffusion length, grain boundary thickness, and the average grain size. In this work we focused on stress changes of deposited films onto the surface consisting of several strips and rows. We consider a surface intersected by the grain boundaries to study influence of the grain boundary size and lattice mismatch on stress in film. We used a three-dimensional molecular dynamics simulations. To simplify calculation, in our model, we use the grain of rectangular shape and the Lennard-Jones (LJ) potential. The LJ potential is not adequate for specific materials. We have chosen this potential to capture the generic feature of such systems. Additionally, the application of simple LJ potential is also motivated by simplification of numerical calculations. Influence of lattice mismatch and grain boundary size on stress will be discussed in detail.

E.EP2.70
13:30
Authors : Juan Rubio-Zuazo 12, Alicia de Andrés2, and Germán R. Castro 12
Affiliations : 1 SpLine Spanish CRG BM25 Beamline at the ESRF BP 220-38043 Grenoble Cedex, France 2 Instituto de Ciencia de Materiales de Madrid-ICMM/CSIC; Cantoblanco, E-28049 Madrid, Spain

Resume : La1-XCaxMnO3–type perovskite-manganese oxides exhibit a wide variety of interesting physical properties which originate from mutual coupling among spin, charge and lattice degrees of freedom. They present, in the Ca doping range between 0.15 and 0.5, a ferromagnetic –paramagnetic (F–M) phase transition accompanied by a metal – insulator (M–I) transition that results in a colossal magneto-resistance behaviour. In bulk La0.7Ca0.3MnO3 (LCMO), the transition temperatures TC and TMI raise for 33% Ca doping level reaching values close to room temperature. It is well-known the premature disappearance of such intrinsic properties for thin films. Typically the TC and TMI transition temperatures decreases as the film thickness is reduced being even absent for ultra-thin films. Such behaviour hampers the potential application of perovskite-manganese oxides in industrial devices. We have studied a series of epitaxial LCMO films with thickness between 2.4 and 27 nm grown on SrTiO3(001) (STO) by dc-sputtering. The magneto-electric measurements show a severe decrease of TC and TMI as the film thickness is reduced. The transition temperatures are absent for films with thicknesses below 2.4 nm. We have performed an extensive study, by X-ray Diffraction and low and high energy X-ray photoelectron spectroscopy, concerning the atomic structure, strain relaxation, oxygen vacancies and compositional and electronic (manganese valence) depth profile as a function of layer thickness.

E.EP2.72
13:30
Authors : Yu. A. Mastrikov1, P. V. Vladimirov2, V.A. Borodin3, A. Gopejenko1, Yu.F. Zhukovskii1, E. A. Kotomin1, A. Möslang2
Affiliations : 1Institute for Solid State Physics, University of Latvia, Kengaraga str. 8, Riga, Latvia 2Institut für Angewandte Chemie, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Karlsruhe, Germany 3 National Research Centre Kurchatov Institute, 1, Akademika Kurchatova pl., Moscow, 123182, Russia

Resume : Reduced activation ferritic-martensitic steels (RAFM) strengthened by yttria precipitates are promising structure materials for future fusion and advanced fission reactors. Oxide dispersion strengthened (ODS) particles hinder dislocation motion effectively resulting in higher strength and better high-temperature creep resistance of ODS steels in comparison to basic materials. Implementation of ODS materials widen the operating temperature, as compared to conventional RAFM steels, as well as they are more radiation resistant. The size, shape and spatial distribution of ODS nanoparticles significantly affect both mechanical properties and radiation resistance. A deep understanding of the mechanism of the ODS particle formation at the atomistic level is essential for ODS steels production [1]. The very initial steps of the ODS particle formation process were modelled by first principles DFT/plane-wave method, as implemented in the computer code VASP 5.3. Stabilization of Y solute atoms in the alpha-Fe lattice was analysed in details. Interaction energies for various combinations of Y solute atoms and vacancies were obtained for use in the future kinetic Monte Carlo calculations. The most probable Y stabilization and precipitation reaction mechanisms were suggested. Y solute atoms create stable complexes with multiple vacancies. Stabilized by vacancies, Y solute atoms exhibit stronger attraction. [1] A. Gopejenko et.al. J. Nucl. Mater., 416, p. 40-44, 2011

E.EP2.73
13:30
Authors : Anders Hallén, Atieh Zamani, Reda Moubah, Gabriella Andersson, Martina Ahlberg,Petra E. Jönsson
Affiliations : Anders Hallén; KTH Royal Institute of Technology, School of ICT, P.O. Box Electrum 229, SE-164 40 Kista-Stockholm, Sweden Atieh Zamani, Reda Moubah, Gabriella Andersson, Martina Ahlberg Petra E. Jönsson; Department of Physics and Astronomy, Uppsala University, Box 516, SE 751 20 Uppsala, Sweden

Resume : Amorphous iron-zirconium (a-FeZr) films have been studied extensively, much due to their interesting magnetic properties. They show soft magnetic features with low coercive field and large magnetic saturation, but typical Curie temperatures for as-prepared samples are around 250 K. However, by for instance, introducing hydrogen, or employing different preparation schemes for the films, it is possible to increase the Curie temperature to above room temperature. The reason for the changes in the magnetic properties is still under discussion, but the direct exchange interaction is very sensitive to the Fe-Fe distance, and the introduction of extra atoms in the structure is believed to increase the Fe-Fe distance thereby enhancing the ferromagnetic properties. In this contribution we will show that the magnetic properties can also be changed by implantation of keV low mass ions at high fluence. In fact, the implantation technique allows a controlled tuning of magnetic properties of the a-FeZr films, for instance, the Curie temperature within a range of 230 to above 400 K using proper choice of ion, energy and fluence [1,2]. In this study a-Fe0.93Zr0.07 thin films of a thickness of about 40 nm are prepared by magnetron sputtering on Si substrates, where the films are sandwiched between two 5 nm thick layers of Al0.7Zr0.3. Ion implantation is then performed at room temperature using a Danfysik implanter and beam currents low enough to prevent any significant sample heating during the implantation. The implantation technique also makes lateral patterning of the surface, using lithographic techniques, possible. In this way one- and two-dimensional structures of various sizes can be prepared which will help to better understand the magnetic behaviour of these films. The role of volume expansion due to the implanted ions and possible swelling effects due to displacement damage for increasing the Fe-Fe distance will be addressed. [1] A. Zamani et al., J. Magnetism and Magnetic Materials 346, 138 (2013) [2] R. Moubah et al., Appl. Phys. Express 6, 053001 (2013)

E.EP2.75
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Nanostructures in silica : William Weber
09:00
Authors : T. Cesca, B. Kalinic, C. Maurizio, C. Scian, P. Mazzoldi, G. Mattei
Affiliations : University of Padova, Dept. of Physics and Astronomy and CNISM, Padova, Italy

Resume : Au-based nanostructures have been the object of strong interest from the scientific community in these years for their linear and nonlinear optical properties. Recently our group demonstrated that enhanced optical functionalities in nanophotonics can be obtained when sub-nanometric Au nanoclusters (made by less than 20 atoms) are formed by ion implantation in silica. Due to quantum confinement effects such molecule-like Au aggregates are characterized by discrete energy levels allowing for efficient radiative relaxation at room temperature. Moreover, the formation of a near-infrared luminescence band correlated to electronic surface states at the Au nanostructures was revealed to be the mechanism that triggers the energy-transfer to photoemitting systems as Er ions and makes sub-nanometric Au nanoclusters very efficient nanoantennas for the Er emission. This has important technological entailments in optoelectronics where many research efforts are being done in these years to increase the small cross-section for Er excitation. In this work we will present the results of some very recent experiments aimed at elucidating the photophysical nature of the interaction between molecule-like Au-based nanoaggregates and Er ions. The results demonstrate that the energy-transfer process is indeed a non-radiative coupling mechanism occurring at very-short range with characteristic length comparable to interatomic distances.

E.EO10.1
09:30
Authors : M. Frégnaux, R. Khelifi, Y. Le Gall, D. Muller and D. Mathiot
Affiliations : Université de Strasbourg, CNRS, Laboratoire ICube (UMR 7357), 23 rue du Loess, BP 20, F - 67037 Strasbourg cedex 2

Resume : Co-implantation, with overlapping implantation projected ranges, of Si and doping species (P, As, B) followed by a thermal annealing step is a viable route to form doped Si nanocrystals (NC) embedded in SiO2. This presentation deals with optical characterizations of both doped and undoped Si NC prepared by this method. The NC effective presence in the oxide layer and their crystallinity is verified by Raman spectrometry. Photoluminescence (PL) and PL excitation measurements reveal quantum confinement effects and a gradual PL quenching with increasing dopant concentrations. In undoped NC, the measured Stokes shift remains constant and its value ~0.2 eV is almost twice the Si–O vibration energy. This suggests that a possible radiative recombination path is a fundamental transition assisted by a local phonon. PL lifetime investigations show that PL time-decays follow a stretched exponential. Using a statistical model for luminescence quenching, a typical radius of ~1.1 nm is obtained for As- and P-doped NC, consistent with our previous atomic probe tomography (APT) analyses. APT also demonstrated that n-type dopant (P, As) are efficiently introduced in the NC core, whereas p-type dopant (B) are located at the NC/SiO2 interface. This observation could explain the failure of the luminescence quenching model to determine B-doped NC size. All together these experimental observations question on possible different carrier recombination paths in P or As doped NC compared to B one's.

E.EO10.2
09:45
Authors : Rens Limpens, Arnon Lesage & Tom Gregorkiewicz
Affiliations : University of Amsterdam (Institute of Physics) Science park 904, 1098 XH, Amsterdam

Resume : Silicon Nanocrystals (NCs) have been widely studied because of their interesting properties and enormous potential for applications in, e.g., photovoltaic industry. The biggest problem is the low emission (photoluminescence, PL) efficiency of Si NCs, which typically does not exceed 15%. This needs to be understood and then improved. In our recent study we have shown that a combination of the presence of a significant amount of defected NCs (termed as "dark" NCs due to the non-emitting character) and energy transfer towards these centers play the dominant role in the efficiency quenching. In the present study, we investigate this energy migration in specially prepared 2- and 3-dimensional (2D, 3D) ensembles of Si NCs where the energy transfer rate is expected to be different. By measuring effective lifetimes and calculating internal quantum efficiencies we are able to visualize and quantize the difference in magnitude of the energy transfer process in the two geometries. We conclude that energy migration is indeed quenched in the 2D system. Combining high-resolution microscopy with PL and spectrally resolved measurements of PL quantum yield, we demonstrate that also the percentage of dark NCs depends on the system's geometry and is smaller for the 2D packing. These findings vouch for a 2D packing of Si NCs in order to increase ensemble emission efficiencies, as in this way energy transfer to defected NCs is mitigated. R.Limpens and T. Gregorkiewicz, J.Appl.Phys, 114 (2013)

E.EP1.50
10:45
Authors : M. Peres [a], M. Felizardo [a], N. Franco [a,b], L.C. Alves [a], E. Alves [a,b], K. Lorenz [a,b], E. Nogales [c], I. López [c], B. Méndez [c], J. Piqueras [c], J. Rodrigues [d], T. Monteiro [d], E. G. Víllora [e], K. Shimamura [e]
Affiliations : [a] Instituto Superior Técnico (IST), Campus Tecnológico e Nuclear, Estrada Nacional 10, P-2695-066 Bobadela LRS, Portugal; [b] IPFN, IST, Portugal; [c] Dpto. Física de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain; [d] Departamento de Física e i3N, Universidade de Aveiro, 3810-193 Portugal; [e] National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan

Resume : β-Ga2O3 is well known for its properties as a transparent conductive oxide for the visible and UV range. The recent success in the production of high quality, single crystalline wafers is now opening the way to develop β-Ga2O3 based electronic and optoelectronic devices. Furthermore, the synthesis of nano- and microstructures as well the optical functionalization with rare earth ions promise new applications in nanotechnology, photonics and sensing. β-Ga2O3 bulk single crystals as well as β-Ga2O3 nanowires (NWs) were implanted with Eu ions with different fluences and at different temperatures. The structural properties were investigated by Rutherford Backscattering Spectrometry/ channeling and X-ray diffraction and the typical 5D0→7Fj intraionic transitions of Eu3+ have been studied by cathodoluminescence, photoluminescence and ionoluminescence. Implantation at room temperature leads to amorphisation for fluences above ~1E15 at/cm2. This lattice damage can be efficiently removed by rapid thermal annealing at ~1100 °C. However, in the case of bulk crystals, Eu could not be incorporated on substitutional sites and a decreased Eu3+ emission is observed by photoluminescence when compared to NWs. Implantation at elevated temperature (~600 ºC) yields a significant reduction of implantation damage, incorporation of Eu on substitutional Ga-sites and an improved optical activation. This result suggests that ion implantation at elevated temperature could be a better process than post-implant thermal treatment.

E.EO11.2
 
Reshaping of nanomaterials by swift heavy ions : Mark Ridgway
14:00
Authors : C. Trautmann1,2, I.Alber1, L. Movsesyan1, 2, A. Spende1,2, M.E. Toimil-Molares1
Affiliations : 1 GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, Darmstadt, Germany; 2 Technische Universit?t Darmstadt, Alarich-Weiss-Str. 4, Darmstadt, Germany

Resume : The ion-track technology based on MeV-GeV ion beams greatly benefits from the fact that each ion projectile creates a cylindrical track with a few nanometers in diameter. The small track size in combination with the large ion range (several tens of ?m) allows the fabrication of high-aspect ratio nanostructures. The track etching process provides great flexibility in adjusting their size and geometry under well controllable conditions [1,2]. Ion-track nanostructures are thus considered as excellent model systems to investigate the influence of size-effects on optical, electrical, magnetic, or thermal properties. The development of suitable techniques to precisely tailor the dimensions, orientation, and surface properties of nanowires is illustrated by several novel examples including: ? Metallic and semiconducting self-supporting 3D nanowire networks of adjustable interconnectivity and high mechanical stability [3]. ? Nanowires synthesized by means of pulsed electrodeposition of Au-Ag-Au segments. Dissolving one of the component creates capacitively and conductively coupled dimers of adaptable gap size and with interesting surface plasmon properties [4]. ? Nanotubes (Al2O3, TiO2, SiO2) of adjustable wall thickness produced by atomic layer deposition in ion track membranes. [1] C. Trautmann, Micro- and Nanoengineering with Ion Tracks, in: Ion beams in Nanoscience and Technology R. Hellborg, H. Whitlow, Y. Zhang (Eds.), Topics Appl. Physics 110, 215?264 (2009) Springer-Verlag. [2] M. E. Toimil-Molares, Beilstein J. Nanotechnol. 3 (2012) 860 ? 883. [3] M. Rauber, I. Alber, S. M?ller, R. Neumann, O. Picht, C. Roth, A. Sch?kel, M. E. Toimil-Molares, W. Ensinger, Nano Lett. 11 (2011) 2304-2310. [4] I. Alber, W. Sigle, F. Demming-Janssen, R. Neumann, C. Trautmann, P.A. van Aken, M.E. Toimil-Molares, ACS Nano 6 (2012) 9711-9717.

E.EO12.1
15:15
Authors : J.H. O’Connell(a), V.A. Skuratov(b), N.Kirilkin(b), J. Neethling(a)
Affiliations : (a)CHRTEM, Nelson Mandela Metropolitan University, Port Elizabeth; (b)FLNR, Joint Institute for Nuclear Research, Dubna, Russia

Resume : Mechanical stresses in swift heavy ion irradiated radiation-resistant insulators are a subject of considerable practical interest in view of the simulation of fission product impact. To date, the build-up and accumulation of stress with swift heavy ion fluence and energy has been studied for a very limited number of ceramics and oxides using mainly X-ray diffraction techniques. Since the radiation damage and correlated stresses induced by swift heavy ions are concentrated within a small volume, surrounding the ion trajectory, it is also interesting to evaluate the stress state of irradiated crystals before and after overlapping of isolated ion track regions. The aim of this study is to collect data of lattice strain as a function of radial distance from the ion track centre using computational methods on TEM micrographs of the ion tracks. This data is of high importance to verify current computational models of track formation based on the temperature spike model. Single crystal Al2O3 crystals were irradiated with 710 MeV Bi and 167 MeV Xe ions and analysed using a JEOL ARM200F TEM

E.EO12.5
17:00
Authors : B.Fraboni1, A.Scidà1, P.Cosseddu2, Y.Q. Wang3, M. Nastasi4, S.Milita5 and A.Bonfiglio2
Affiliations : 1Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy 2Dipartimento di Ingegneria Elettrica ed Elettronica, Università di Cagliari, piazza d’Armi, 09123 Cagliari, Italy and CNR-INFM S3 via Campi 213/a 41100 Modena 3Los Alamos National Laboratory MS-K771 Los Alamos NM 87545 USA 4 Center for Energy Sciences Research, University of Nebraska –Lincoln, Lincoln, NE U.S.A 5 IMM-CNR Bologna

Resume : The performance of organic electronic devices is steadily improving thanks to the advancement in understanding and controlling the organic material molecular structure and electron transport properties. Yet, a few major issues still need to be addressed, such as the achievement of an efficient charge carrier injection. The implementation of low contact resistance devices usually relies on interface physics (matching the metal electrode work function to the molecular energy levels of the semiconductors), or on dedicated device architectures. The electrical doping of organic films can be a very attractive way to further improve the efficiency of organic devices and ion implantation, the process often used to this aim in the fabrication of inorganic semiconductor devices, has not been yet applied to small molecule organic semiconductors on to organic materials. We report on the effects of low energy (30keV) ion implantation on thin films of Pentacene, carried out to investigate the efficacy of this process in the fabrication of organic electronic devices. Two different ions, Ne and N, have been implanted and compared, to assess the effects of a different reactivity within the hydrocarbon matrix. A strong modification of the electrical conductivity, stable in time, is observed following ion implantation. This effects is significantly larger for N implants (up to 8 orders of magnitude), that are here shown to introduce stable charged species within the hydrocarbon matrix, not only damage as is the case for Ne implants. Fully operational Pentacene thin film transistors have also been implanted and we show how a controlled N ion implantation process can induce stable modifications in the threshold voltage, without affecting the device performance. We have monitored the effectiveness of low-energy ion implantation in controlling and stabilizing the organic thin film resistivity over a long time (over 2000 hours), proving how ion implantation can be safely carried out on fully operational OTFTs. The electrical properties of the Pentacene layer and of the OTFT have been investigated by means of current-voltage and photocurrent spectroscopy analyses, while the structural modification induced by ion implantation have been characterized by depth resolved X-ray Photoemission Spectroscopy analyses.

E.EO13.4
17:15
Authors : P.A.Karaseov1, A.I.Titov1, S.Kumar2, A.Tripathi2, D.K.Avasthi2, S.Mohapatra3
Affiliations : 1 State Polytechnic University, St.Petersburg, Russia 2 Inter University Accelerator Center, New Delhi, India 3. Guru Gobind Singh Indraprastha University, New Delhi, India

Resume : Ion beams are increasingly being used as a tool for synthesis and modification of nanostructures. It is demonstrated that ion beams can be used for synthesis of graphitic clusters to engineer the sp3/sp2 –bonding ratio and stress in insulating carbon thin films. Such transformation of insulating, diamond-like (sp3-bonded) carbon into conducting, graphite-like (sp2-bonded) carbon within the ion tracks has been demonstrated. Recently, it has been shown that swift heavy ion irradiation of carbon films results in the formation of conducting graphitic nanowires of about 8 nm in diameter embedded within the insulating carbon matrix. Use of swift heavy ion irradiation as a tool to synthesize conducting nanowires has been explored by a few groups. The field emission properties of carbon films are mainly dependent on the chemical bonding structure and the doping with metals (Au, Ag, Ni) into the carbon matrix. Modification of such doped material along ion track by swift heavy ion irradiation is of great interest since it gives not only the way to engineer the sp3/sp2 –bonding ratio and stress in the film, but can give nanowires with significantly increased conductivity. In this contribution the route of swift heavy ion irradiation of carbon films combined with its doping for achieving highly conducting ion tracks in insulating carbon films will be presented. This work is supported by Russian RFBR (grants № 12-08-01197 and 13-02-92709) and DST of India.

E.EO13.5
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11:00
Authors : A. Janse van Vuuren(a), V. A. Skuratov(b) J.H. Neethling(a), V.V. Uglov(c) and S. Petrovich(d)
Affiliations : (a)CHRTEM, NMMU, Port Elizabeth, South Africa, (b)FLNR, JINR, Dubna, Russia, (c)BSU, Minsk, Belarus, (d)VINCA Institute of Nuclear Sciences, BU, Belgrade, Serbia

Resume : Recent studies have shown that swift heavy ion irradiation may significantly modulate hydrogen and helium behavior in certain materials. This phenomenon is of considerable practical interest for various ceramics and semiconductors, specifically for candidate materials for use as inert matrix fuel hosts (IMs). IMs accumulate He via (n,) reactions and will also be subjected to high energy fission fragments (FFs) in the nuclear reactor environment. The inherent properties of ZrN has led to its identification as a candidate IM. Certain studies have indicated that nanocrystalline (nc) materials have improved radiation tolerance compared to their micro- and single-crystalline counterparts. This suggests that nc-ZrN may have a superior radiation tolerance. In this study low energy He ions were used to simulate -particles and high energy Xe and Bi ions were used to simulate FFs. The combined effects of low and high energy radiation were also studied. TEM and SEM were used to study nc-ZrN irradiated with 30-40 keV He, 167 MeV Xe and 695 MeV Bi ions to fluences of 5×1016 cm-2, 2.65×1014 cm-2 and 1.5×1013 cm-2 respectively. The irradiated samples were annealed at temperatures between 600 and 1000 °C. He irradiation did not lead to amorphization of unannealed nc-ZrN. Post irradiation heat treatment resulted in blistering at depths corresponds to the end-of-range of the He ions. He/Xe irradiated samples revealed that the electronic excitation effects (EEEs) resulting from high energy Xe ions suppress He blister formation. nc-ZrN is prone to the formation of He blisters, which may lead to material failure and is therefore of concern for materials with nuclear applications. These effects may however be suppressed by the EEEs from high energy heavy ions.

E.EO15.2
11:30
Authors : C. Pardanaud1, Y. Addab1, C. Martin1, N. Mellet1, G. Giacometti1, P. Roubin1, B. Pegourie2, M. Oberkofler3, M Koppen3, T. Dittmar3, Ch. Linsmeier3, C. Hopf4, T. Schwarz-Selinger4, W. Jacob4
Affiliations : 1 Aix-Marseille Universit?-CNRS, PIIM, 13397 Marseille cedex 20, France; 2CEA, IRFM, 13108 Saint-Paul-lez-Durance, France; 3 Forschungszentrum J?lich GmbH, Institut f?r Energie- und Klimaforschung - Plasmaphysik, 52425 J?lich, Germany 4Max-Planck-Institute f?r Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching, Germany.

Resume : One promising way to produce energy from nuclear fusion reaction is to magnetically confine a hot (D, T) plasma in thermonuclear fusion devices (called tokamaks) and to heat it to ignition. One of the inner walls? role is to transfer the heat loads produced by the fusion reaction to a cooling loop and then to a turbine for producing electricity. In the tokamaks, interactions between plasma and walls lead to impurity transport in the edge machine together with material migration/mixing. Depending on the location in the machine, the impinging particle flux and energy, the initial structure of the material? wall?s temperature is changed, affecting the efficiency of the fundamental mechanisms occurring. Then, it is a challenging question to predict what will be the walls? hydrogen content. This point has been achieved for carbon walls as many studies have yet been done. Especially, a campaign involving the Tore Supra tokamak has been dedicated to measure both the H and C behavior at the scale of the machine and on many years. However, due to the good affinity existing between C and H isotopes leading to a severe safety issue (namely, tritium retention), carbon is not envisaged for the next step machine: the ITER project. Be and W, in which H isotopes can also be retained, have been chosen as the wall materials. For these elements, many studies have to be done before we can be predictive. In this study, we will present the advantage of using Raman spectroscopy at the micron scale (H bonding, structure/defect sensitive, non destructive,?) for fusion applications. As examples, we will use Tore Supra carbon tiles, beryllium implanted with deuterium ions resulting in the creation of D containing nanometric height domes, and tungsten oxides implanted with hydrogen ions.

E.EO15.4