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2014 Fall Meeting

MATERIALS FOR OPTICS AND OPTOELECTRONICS

B

Organized nanostructures and nano-objects: fabrication, characterization and applications

The symposium covers all the scientific and technological aspects related to the synthesis of semiconductor or metallic nanodots and nanowires, with special emphasis on the multiscale organization and auto-organization of these nano-objects in ordered structures, in view of their future integration in functional devices.

Scope:

Due to their appealing size dependent properties, semiconductor and metallic nano-objects (nanocrystals, nanowires) have been predicted to be used as technological boost in various fields including nano-electronics, optoelectronics, photonics, magnetism, and photovoltaic. The capability to control size, shape, composition and doping of these nano-objects is crucial to finely tailor their properties. Nevertheless the future implementation of these elemental building blocks in functional devices at nano-scale requires precise control of the organization of the nano-objects in terms of density and relative positioning within well organized structures. The capability to fabricate ordered arrays of nano-objects and to precisely organize the nano-objects on appropriate substrates or inside various matrices is the key point to support the technological development of new device concepts with predictable characteristics based on these novel nano-materials. Following a very successful symposium organized in 2012, this symposium intends to draw on previous experience that demonstrated the wide interest of these specific topics. In particular the analysis of the participants and presentations clearly indicated that a special focus on multiscale fabrication, organization and auto-organization is requested by the scientific community working in the field of nanotechnology. The symposium will provide the opportunity to present insights on advanced nano-structures and nano-device architectures at different stages of development. The symposium is open to all experimental and theoretical results on organized nano-structures, aiming to control the main parameters of the nano-objects in relation with their tunable properties and functionalities. As a consequence the symposium is expected to create a platform in order to bring together researchers coming from academia and industry and to stimulate interactions among scientists, engineers and students working on all the aspects of semiconductor and metallic nano-structures, from fundamental physics and material science issues to the final application in functional devices.

Hot topics to be covered by the symposium:

This symposium will include but will not be limited to the following topics:

  • Synthesis of nano-structures: Top-down and Bottom-up processes
  • Metal and semiconductor nano-structures
  • Self and induced organization of nano-structures
  • Nano-structures on surface and in volume
  • Doping issues in nano-structures
  • Advanced methodology to control synthesis and positioning of nano-structures
  • Light emission and optical gain in semiconductor nano-structures
  • Advanced nano-lithographic strategies based on self assembly approaches
  • Applications of nano structure in microelectronics, optoelectronics and photovoltaics

List of invited speakers:

  • Luca Boarino, INRIM, (Italy): "3 dimensional nanostructures for metrology and surface analysis"
  • Guillaume Fleury, LCPO, University of Bordeaux, (France) “Directed Self-Assembly of Block Copolymers for Lithographic Applications: from Materials Design to Pattern Transfer Demonstration”
  • Michele Laus, Universita del Piemonte Orientale, (Italy) "Structural Design and Chemical Implications of the Macromolecular Systems for Block Copolymer-Based Technologies"
  • Erik Garnett, FOM-Institute for Atomic and Molecular Physics, Amsterdam (The Netherlands), “Solar Highways: core-shell nanowires for high-efficiency, low-cost solar conversion”
  • Manuel Schnabel, Fraunhofer Institute for Solar Energy Systems, Freiburg“Self-Assembled Silicon Nanocrystal Arrays for Photovoltaics“
  • F. Ruffino, CNR – IMM, Catania, Italy “Approaches for nano-structuring and patterning metallic films”
  • Stefano Cabrini, Berkeley Lab “Direct Nano imprinting of High Refractive Index Material for Printable Photonic Devices”
  • Leonhard Grill, University of Graz, Austria “Assembly and manipulation of functional molecules at the atomic-scale”
  • Joel Moser, ICFO Spain “Force detection and frequency fluctuations in carbon nanotube mechanical resonators”
  • Dominique Drouin, UMI-LN2 Canada/Québec “Integration of nanoelectronic devices within BEOL of CMOS circuit”  

List of scientific committee members:

  • S. Spiga, Laboratorio MDM, IMM-CNR, Agrate Brianza (Italy)
  • A. W. Weeber, ECN - Solar Energy, Petten (Holland)
  • F. Falk, Photovoltaic Systems Dept. Institute of Photonic Technology, Jena (Germany)
  • C. A. Ross, Massachusetts Institute of Technology, Cambridge (USA)
  • A. Garcia Santiago, Universitat de Barcelona, Barcelona (Spain)
  • J. Valenta, Charles University, Prague (Czech Republic)
  • S. Schamm-Chardon, CEMES/CNRS, Toulouse (France)
  • T. Baron, Laboratoire des Technologies de la Microelectronique-CNRS (France)
  • D. Bimberg, Berlin’sTechnical University, Berlin (Germany)
  • P. Dimitrakis, Institute of Microelectronics, NCSR ‘Demokritos’, Athens (Greece)
  • J.A. Yater, Freescale Semiconductor Inc., Austin (USA)
  • D. Hiller, IMTEK, Freiburg University, Freiburg (Germany)
  • J. M. de Teresa, Zaragoza University, Zaragoza (Spain)
  • M. Buljan, Rudjer Boskovic Institute, Zagreb (Croatia)
  • Paolo Bettoti, University of Trento, Trento (Italy)

Proceedings:

Selected contributions will be published, after peer-review process, as regular journal articles in a special issue on "Organized Nanostructures" to appear in PSS(a)‏

Young scientists awards:

Financial support will be provided to young scientists (PhD students). In order to apply, they are requested to send an application to the organizers of the conference by e-mail. The selection will be performed on the basis of the scientific evaluation of the submitted abstracts.  

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Low Dimensional Carbon Related Materials : Erik Garnett
09:00
Authors : Joel Moser, Johannes Güttinger, Alexander Eichler, Mark Dykman, Adrian Bachtold
Affiliations : ICFO – The Institute of Photonic Sciences Mediterranean Technology Park Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain; ICFO – The Institute of Photonic Sciences Mediterranean Technology Park Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain; ICFO – The Institute of Photonic Sciences Mediterranean Technology Park Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain; Department of Physics and Astronomy Michigan State University Biomedical Physical Sciences Bldg. 567 Wilson Road, Room 4244 East Lansing, MI 48824-2320; ICFO – The Institute of Photonic Sciences Mediterranean Technology Park Av. Carl Friedrich Gauss, 3 08860 Castelldefels (Barcelona), Spain

Resume : Because of their low mass and of their small dimensions, carbon nanotube mechanical resonators offer many exciting opportunities in sensing applications. These traditionally include mass sensing at the single atom level [1, 2], and charge sensing [3, 4]. Nanotube resonators can also act as very sensitive force detectors. I will present our recent force sensing experiments in which the force noise experienced by nanotube resonators has a density measured to be as low as 10E-21 Newton per square root of Hertz [5]. This force noise has a thermal origin and is associated with the Brownian motion of the nanotube at 1 K. To detect the low amplitude vibrations of the nanotube in the Brownian motion regime at such a low temperature, we employ a sensitive method based on correlated electrical noise measurements, in combination with parametric down-conversion. We quantify the force sensitivity of our resonator by applying a known capacitive force. Further enhancing the force sensitivity of our resonators requires improving their quality factors. Indeed, the resolution in force detection with a mechanical resonator is ultimately limited by thermal noise that comes from the coupling of the resonator to a thermal reservoir. This thermal noise is related to the quality factor of the resonator by the fluctuation-dissipation theorem. By measuring the Brownian motion of an ultra-clean nanotube at a cryostat temperature of 30 mK, we observe quality factors as high as 5 million [6]. These are comparable to the highest quality factors reported in mechanical resonators of much larger size. Interestingly, our statistical study of thermal resonances reveals that fluctuations of the resonant frequency induced by the environment lead to significant spectral broadening. This means that the quality factors we observe are currently limited by frequency noise of non-thermal origin induced by the measurement setup. Hence the measured quality factors may still be lower than the intrinsic quality factors of nanotube resonators, which are related to the small-amplitude ring-down time. The combination of ultra-low mass and high quality factor offers new opportunities for ultra-sensitive detection schemes with nanotubes, such as the resonant force detection of a few nuclear spins attached to a nanotube vibrating in a magnetic field gradient. [1] K. Jensen, K. Kim, and A. Zettl. An atomic-resolution nanomechanical mass sensor. Nature Nanotech. 3, 533-537 (2008). [2] J. Chaste, et al. A nanomechanical mass sensor with yoctogram resolution. Nature Nanotech. 7, 301-304 (2012). [3] G. A. Steele, et al. Strong coupling between single-electron tunneling and nanomechanical motion. Science 325, 1103-1107 (2009). [4] B. Lassagne, et al. Coupling mechanics to charge transport in carbon nanotube mechanical resonators. Science 325, 1107-1110 (2009). [5] J. Moser, et al. Ultrasensitive force detection with a nanotube mechanical resonator. Nature Nanotech. 8, 493-496 (2013). [6] J. Moser, et al. Nanotube mechanical resonators with quality factors reaching 5 million. Submitted.

B.1.1
09:30
Authors : A. Palla Papavlu1,2, J. Chen1, A. Wokaun1, T. Lippert1, M. Dinescu2
Affiliations : 1) General Energy Research Department, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland 2) Lasers Department, National Institute for Lasers, Plasma and Radiation Physics, 077125 Magurele, Romania

Resume : The capability to spatially control the deposition of different materials in solid and liquid phase onto various types of substrates is important for the development of sensors. One suitable technique for the deposition of different materials in solid and liquid phase onto various types of substrates with high spatial resolution (a few microns) is laser-induced forward transfer (LIFT). In LIFT, a laser beam is focused through a transparent support plate onto the backside of a photodegradable polymer (triazene polymer) thin film coated with the material to be transferred. Each single laser pulse promotes the transfer of the thin film material onto a receiver substrate that is usually placed parallel and facing the thin film at a short distance. The triazene polymer layer, also called dynamic release layer (DRL) or sacrificial layer, has the purpose to improve the process efficiency and to reduce the risk of damaging the layer to be transferred. In this work, the developments in DRL assisted LIFT of complex materials such as carbon nanotube networks for applications as recognizing elements in miniaturized chemiresistor devices are presented. As the functionality of such sensors depends on the applied laser source, target material, and transfer geometry, first an optimization of the process parameters is reported. Following a morphological and structural characterization of the active material, the performance, i.e. the sensitivity, resolution, and response time of the laser-printed devices was evaluated by exposure of the sensor arrays to different toxic vapors. Different sensitivities and selectivity to the selected organic compounds i.e. ammonia, etc. have been measured proving the feasibility of LIFT for applications in sensors.

B.1.2
09:45
Authors : Agnieszka Lekawa-Raus, Krzysztof K. Koziol
Affiliations : Department of Materials Science and Metallurgy, University of Cambridge, UK

Resume : The recent rediscovery of the unique potential of carbon initiated extensive research in the area of new carbon structures. In particular, carbon nanotubes have gained widespread attention owing to their exceptional physical properties. An important application which could particularly benefit from the use of carbon nanotubes is electrical wiring [1]. This is mainly due to stunning electrical and mechanical performance of nanotubes combined with low density, as well as great abundance of carbon element and potentially very low cost of production of nanotubes. The macroscopic material with such characteristics could make a perfect electrical conductor and improve the performance of our energy distribution systems and electrical machines. The recent manufacture of macroscopic wire-like assemblies made purely of CNTs – CNT fibres – opened up new prospects in this area. The development of fibre spinning processes and engineering of the produced fibres led to the development of first nanotube electrical wires and electrical machines. The following presentation will demonstrate the most recent achievements of this technology as well as discuss prospects and challenges in the field.[1-3] [1] Lekawa-Raus et al. Adv. Funct. Mat. (2014) DOI:10.1002/adfm.201303716 [2] Kurzepa et al. Adv. Funct. Mat. (2014), 24, 619. [3] Lekawa-Raus et al. Carbon (2014), 68, 597.

B.1.3
11:30
Authors : Ewa Dumiszewska, Piotr Knyps, Aleksandra Krajewska, Marek Wesołowski, Włodzimierz Strupiński
Affiliations : Institute of Electronic Materials Technology Wolczynska 133, 01-919 Warsaw, Poland

Resume : III-V semiconductor compounds, whose electrical and optical properties are suitable for solar energy conversion, are the most promising candidates for realizing solar cells with efficiencies of 50% and more. Free-standing semiconductor nanowires have been recently considered for application in photovoltaic devices. In this work we studied growth of GaAs and InP nanowires. In the case of GaAs nanowires both (100) and (111) GaAs substrates were used. Colloidal Au with diameter ~30-40nm prepared by the Turkevich method acted as a catalyst. Tetrachloroauric acid solution was heated to the boiling point. Next, solution of reducing and stabilizing agent (sodium citrate) was added and heated until its color changed. InP nanowires were grown on both InP (111) and (100) substrates with and without the nanoparticle catalyst. InP and GaAs nanowires measuring 20-200nm in diameter and 10?m in length were successfully grown in an AIX 200 MOVPE reactor, with TMGa, TMIn, PH3 and AsH3 as source gases.

B.2.2
12:15
Authors : J. Sadowski (1,2), A. Siusys (2), S. Kret (2), K. Gas (2), W. Szuszkiewicz (2), M. Sawicki (2)
Affiliations : (1) MAX-IV laboratory, Lund University, P.O. Box 118, 221 00 Lund, Sweden; (2) Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warszawa, Poland

Resume : Core shell nanowire (NW) structures with (In,Ga)As ternary alloy cores and (Ga,Mn)As ferromagnetic semiconductor shells were grown by molecular beam epitaxy (MBE) on GaAs(111)B substrates in the Au-catalyst induced vapour-liquid-solid growth mode. Both core and shell materials crystallized in the wurtzite structure, which has not been investigated yet in the case of (Ga,Mn)As. The MBE growth of the (In,Ga)As cores has been performed at high temperatures (500 C), whereas the shells have been deposited at much lower temperatures of about 230 C. This low temperature growth of (Ga,Mn)As shell is essential to obtain sufficiently high Mn content (above 1%) needed to assure ferromagnetic coupling in (Ga,Mn)As solid solution. The composition of the (In,Ga)As cores was chosen in such a way that the NW shells are under tensile strain, which promotes the perpendicular orientation of their magnetic easy axes. The structural properties of the NWs have been studied by high resolution transmission microscopy techniques, their optical and magnetic properties by Raman scattering and SQUID magnetometry, respectively. The latter revealed inferior magnetic characteristics of the shells in comparison to those commonly observed in planar (Ga,Mn)As layers. The possible mechanisms responsible for that will be discussed. The examples of NWs with multi-shell structures with the shells comprising (Al,Ga)As ternary alloy will also be presented.

B.2.5
 
Metallic Nanostructures : Michele Perego
14:00
Authors : F. Ruffino, M. G. Grimaldi
Affiliations : F. Ruffino, M. G. Grimaldi Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123 Catania, Italy and MATIS CNR-IMM via S. Sofia 64, 95123 Catania, Italy

Resume : Metal thin films and metal nano-structures (MNs) attract much interest because of their wide applications in several technological areas. In particular, fabrication of functional arrays of MNs with specific patterns is crucial for the development of next generation devices. In contrast to top-down methods, the “bottom-up” ones assemble the atomic constituents in organized structures. It is desirable to develop low-cost, versatile and large-area-production approaches for the bottom-up fabrication of MNs by self-assembly processes at surfaces. In this context, the dewetting process of metastable thin films from a solid substrate is a topic of interest. Metal films on non-wetting substrates can undergo to thermal, pulsed laser, ion, electron-beam induced dewetting to form MNs characterized by spatial patterns determined by the boundary conditions. In this work, an overview of some dewetting-based approaches for the production of patterned and non-patterned arrays of MNs and films will be given. The following topics will be discussed: 1) exploitation of laser irradiation of Au films on Si to produce core-shell nanoparticles; 2) exploitation of the thickness-dependent nature of the dewetting process to produce size-controlled arrays of Au and Ag nanoparticles; 3) exploitation of the thermal-induced dewetting process to decorate graphene sheets and SiO2 nanowires by Au nanoparticles; 4) exploitation of the dewetting properties of polymer layers to pattern deposited thin Au films.

B.3.1
17:15
Authors : Bartlomiej Kolodziejczyk, Orawan Winther-Jensen, Shenghuang Lin, Qiaoliang Bao, Bjorn Winther-Jensen
Affiliations : Department of Materials Engineering, Monash University, Clayton, 3800 Victoria, Australia

Resume : Conducting polymers are a rapidly developing field in materials science. They have found application in organic electronics, corrosion protection, tissue engineering and non-linear optical devices amongst many others. It has been a persistent challenge to develop ordered conducting polymer nano- and micro- structures with a high active area. Herein, we report a characterisation of a network of nanometre-sized walls (nano-walls) formed on the surface of a conducting co-polymer composite film based on bithiophene and terthiophene, prepared using vapour-phase polymerisation (VPP). The density and dimensions of the nano-walls are able to be tuned in order to suit a specific application. The nano-walls present on the film surface increase the capacitance of the coating up to 3.4 times, making it a promising candidate for organic electronics and energy based applications. Additionally, the nano-walls proved to be a great candidate for waveguides making them useful for photonic applications. Here we propose a two-step growth mechanism, which includes the reduction of Fe(III) and part of the tosylate ligand present in the Fe(III) p-toluene sulphonate oxidant. This is the first report of a self-assembling conducting polymer material with nano-wall features induced by the conditions set during VPP. By tuning the polymerization parameters we can create a range of nano-structures including nano-walls, nano-spikes, nano-sheets and nano-sponges to suit application requirements.

B.4.5
17:45
Authors : Gaehang Lee, Doo Ri Bae, Gi-Ra Yi
Affiliations : Korea Basic Science Institute (Gaehang Lee); Korea Basic Science Institute (Doo Ri Bae); School of Chemical Engineering, Sungkyunkwan University (Gi-Ra Yi)

Resume : We present the gram-scale synthesis of hydrophobic gold nanoparticles and a colorimetric system for aqueous HCl detection by electrostatically-induced attraction of the Au nanoparticles. The hydrophobic Au nanoparticles can produce a size change of 440% from 10 nm to 54 nm through the control of the volume ratio of the co-surfactants. In our system, the size change within a wide range is attributed to the high controllability of a surfactant in particle growth. It is very important to size change Au nanoparticles in one synthetic system because the surface energy and the optical properties of gold nanoparticles depend considerably on their size. Electro-sterically stabilized gold suspensions were employed in a colorimetric system for the detection of strong acid in water. When the hydrochloric acid solution higher than critical concentration was injected, particles were quickly aggregated and precipitated, creating a clear solution from the colored suspension. The minimum concentration of dramatic color change was at 5 ppm level of hydrochloric acid, in which the largest colloidal gold nanoparticles (54 nm) were used. Furthermore, because of their steric repulsive soft layer on particles, particles could be reused for further detection experiments after regeneration by the simple pH-neutralization and washing process.

B.B I.3
17:45
Authors : R. А. Shkarban, Ya. S. Peresunko, E. P. Pavlova, S. I. Sidorenko, A. Csik*, Yu. N. Makogon
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine y.makogon@kpi.ua *Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), H-4001 Debrecen, P. O. Box 51, Hungary

Resume : Thermoelectrics is priority direction of development of science and technology and bases on direct conversion of waste heat into electricity and on the contrary thermoelectric cooling. Antimonide of CoSb3 is perspective thermoelectric material. Formation of phase composition and structure is investigated in nanoscaled films CoSbх(30 nm) (1,82 ≤ х ≤ 4,16) deposited by the method of molecular-beam epitaxy on the substrates of the oxidated monocrystalline silicon at room temperature and 200oC and following annealing in vacuum in temperature range of 300 700оС. Chemical composition of films was determined by Rutherford backscattering spectrometry. Phase composition and structure were characterizated by X-ray diffraction. It is established that the films after the deposition are amorphous state on cold substrate and polycrystalline without texture on heat substrate. Crystallization of amorphous CoSbх films occurs at heating in temperature range of » 140 – 200оС. In the films with bigger Sb amount the temperature range of crystallization increases and shifts to the side of higher temperature. Intensive process of Sb evaporation both excess and from antimonides is observed at annealing of x-ray amorphous films above 300оС and at annealing of polycrystalline films above 450-500оС that will lead to increase in amount of СоSb and СоSb2 phases and decrease in СоSb3 amount. The authors would like to thank Prof. M. Albrecht and Dr. G. Beddies and workers from Chemnitz University of Technology (Germany) for sample preparation, assistance in conduction of investigations and discussion of results.

B.B I.5
17:45
Authors : Małgorzata Norek, Maksymilian Włodarski, Piotr Matysik, Wojciech J. Stępniowski
Affiliations : Military University of Technology

Resume : For several decades the plasmonic behavior of materials have been almost exclusively studied in visible region. UV plasmonics is of particular interest because of large variety of applications where the higher energy plasmon resonances would advance scientific achievements, including surface-enhanced Raman scattering (SERS) with UV excitation, ultrasensitive label-free detection of important biomolecules absorbing light in the UV, or the possibility for exerting control over photochemical reactions. In UV nanoplasmonics aluminum (Al) can play a leading role due to its advantageous electronic properties. Yet, there is still lack of reproducible method to obtain Al nanostructures with desired parameters and suited for large-scale production. Al nanoconcave arrays can provide a way to overcome these limitations. The regular Al nano-concave arrays can be fabricated by means of hard anodization (HA) processes at high voltages on arbitrarily large area. The method enables the preparation of concaves with well-controlled geometrical parameters such as interpores distance (Dc) or regularity ratio (RR). Al concaves with properly designed Dc and RR demonstrate plasmonic properties in UV/violet region with controllable plasmon resonances. Moreover, the material is very promising with respect to many important applications in UV range, such as improvement of blue/UV light extraction in LEDs, anti-reflecting substrates enhancing light absorption by active layer in solar cells, or biochemical sensing.

B.B I.9
17:45
Authors : M.A.Osman 1, A.A.Othman1,, Waleed A. El-Said2, A.A.Abu-shely1, Ahmed G.Abdel rahim1
Affiliations : 1 Physics Department, Faculty of Science, Assiut University. 2 Chemistry Department, Faculty of Science, Assiut University.

Resume : ZnS nanocrystals were prepared by chemical co-precipitation method using zinc acetate (Zn (Ch3COO) 2) and sodium sulfide (Na2S) as ionic precursors and EDTA as capping agent. The samples were annealed in air for 3 h in steps of 100 ?C in the temperature range of 125?700 ?C. The effect of annealing temperature (Ta) on the morphological, structural and optical properties of ZnS nanoparticles was investigated using x-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), optical absorption spectroscopy (OAS), selected area electron diffraction (SAED) and fourier transform infrared (FTIR) spectroscopy. Analysis of XRD patterns for as prepared and annealed samples using Scherrer equation showed that increasing (Ta) leads to an increase in the crystallite size (D) from 2.67 to 19.6 nm. A large discrepancy is found between the mean values of the particle size calculated from XRD pattern and that obtained from TEM images. In addition, it was observed that the obtained values of lattice parameters from (HRTEM) and (SAED) pattern are in good agreement with that deduced from (XRD) analysis. Furthermore, annealing process at 600 oC and 700 oC results in complete phase transformation from as prepared ZnS cubic structure to ZnO hexagonal structure. Analysis of the XRD patterns, SAED, HRTEM and FTIR spectra confirmed this phase transition. Moreover, analysis of the optical absorption spectra according to Tauc's equation (αhν)2 = A(hν − E_g^opt) for direct allowed optical transition indicates noticable decrease in the direct band gap E_g^opt from 4.70 to 3.22 eV with increasing Ta.

B.B I.10
17:45
Authors : G. P. Dimitrakopulos1, N. Florini1, J. Kioseoglou1, T. Walther2, S. Germanis3, Z. Hatzopoulos3, N. T. Pelekanos3, Th. Kehagias1
Affiliations : 1 Physics Department, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece; 2 Department of Electronic and Electrical Engineering, University of Sheffield, Mappin St, Sheffield S1 3JD, UK; 3 Microelectronics Research Group (MRG), IESL, FORTH, GR-71110 Heraklion Crete, Greece; Materials Science and Technology and Physics Departments, University of Crete, Heraklion Crete, Greece

Resume : High resolution and scanning transmission electron microscopy (HRTEM/STEM) were employed to elucidate the structural features and strain properties of piezoelectric InAs quantum dots (QDs), showing extensive potential for single photon emission and photon entanglement. QDs were grown by plasma-assisted molecular beam epitaxy (PAMBE), either on the surface or embedded in (211)B GaAs, over a 40x period (1.5 nm AlAs)/(2.3 nm GaAs) superlattice. Combined plan-view and cross-sectional TEM/HRTEM observations showed that uncapped QDs exhibit a pyramidal anisotropic shape, elongated along the [-111] direction, with a base-aspect-ratio from 1.2 to 1.4 and 5-15 nm height. Embedded InAs QDs are also elongated along the same direction with a 6-10 nm length, while their height is of the order of 2 nm to 4 nm. The strain properties of the InAs QDs were investigated by geometrical phase analysis (GPA). The surface InAs QDs were almost strain-free due to the introduction of misfit dislocations at the InAs/GaAs interface. Conversely, HRTEM imaging showed a full in-plane registration of the embedded QDs without any associated line defects, suggesting fully strained nanostructures. Constructed chemical maps of the embedded QDs showed a gradual increase of the In content from the base of the QDs towards their apex. Acknowledgments: Research co-financed by the EU (ESF) and Greek national funds - Research Funding Program: THALES, project NANOPHOS.

B.B I.15
17:45
Authors : Beata Kalska-Szostko, Urszula Wykowska, Dariusz Satuła
Affiliations : Institute of Chemistry, University of Bialystok, Hurtowa 1, 15-399 Bialystok, Poland; Faculty of Physics, University of Bialystok, Lipowa 41, 15-424 Bialystok, Poland

Resume : Magnetic nanowires are one of the type of elongated nanomaterials. Their unsymmetrical structure adds some interesting features to the one which are well known from the nanoparticle system. Magnetic nanowires, with their extraordinary properties, become popular material due to the fact, that they can be used for site-specific targeting and delivery through external magnetic field differently than spherical nanoparticles. In many cases the properties of fine materials depend on the way of fabrication procedure, their crystal structure, size, surface modification, solution composition etc. Therefore nanowires system is rather complex one. Modification of the electronic state of the nanoobjects can originate in the presence of a layered or granular inert structure. As a result ,the modifications of the properties can be totally different due to its nature. In such instance each nanoparticle can be treated separately and it has very complex structure: core, interface core-shell, shell, interface shell-neighborhood, neighborhood. Devices based on self-organized nanowires can lead to the fabrication of very promising flexible low cost and large dimension sensors. In the paper analysis of the magnetic nanowires will be presented with magnetic moment orientation tunable by composition. Structural characterization will be performed by XRD, TEM, SEM while magnetic moment orientation will be determined by Mössbauer spectroscopy.

B.B I.16
17:45
Authors : A.M. Titenko (1), L.D. Demchenko (2)
Affiliations : (1) Institute of Magnetism, Kyiv, Ukraine; (2) National Technical University of Ukraine'' Kyiv Polytechnic Institute'', Kiev, Ukraine

Resume : Aging Cu-Mn-Al alloys, which differ in the original magnetic characteristics, undergo martensitic transformation (MT). The dispersive ferromagnetic particles located in non-ferromagnetic matrix can be formed by heat treatment. The sufficiently small coherent Cu2MnAl particles, whose size is substantially less than martensite critical nucleus, are formed in (Cu-Mn)3Al matrix during the aging of Cu-Mn-Al alloy. The elastic shear deformations of particles within martensite crystals cause the changes in their magnetic properties at MT in contrast to properties of particles located in high-temperature phase. The MT characteristic temperatures and hysteresis mainly depend on alloy composition and structure of forming phases, which in their turn can undergo sufficient changes during heat treatment. The effect of austenitic phase aging in Cu-Al-Mn alloys at uniaxial tension on a value of deformation related with growth and disappearance of thermoelastic martensitic crystals in field of mechanical stress was studied. The deformation behaviour of this system alloys in different structural states was considered. The maximum value of superelastic deformation corresponds to the minimum width of MT temperature hysteresis. Since the width of the hysteresis depends strongly on the volume fraction and particle size, there is a possibility of changing the heat treatment regime to control both the hysteresis width and the superelastic strain value of shape memory aging alloys.

B.B I.17
17:45
Authors : A.I.Savchuk, I.D.Stolyarchuk, O.A.Savchuk, V.I.Garasym
Affiliations : Department of Physics of Semiconductors and Nanostructures, Chernivtsi National University, 2 Kotsubynsky Str., 58012 Chernivtsi, Ukraine

Resume : Over the past few decades, the II-VI semiconductors nanoparticles were prepared by several chemical and physical routes. The advantage of the physical process for synthesizing II-VI based semiconductors nanoparticles is that one can obtain materials with different sizes as well as with different band gaps and band gap can be tuned by varying size of NCs. In addition, II-VI semiconductor compounds have another functionality as a basic matrix for diluted magnetic semiconductors (DMSs), where a fraction of semiconductor cations are replaced by transition metals (3d- or 4f- elements). Dopant-carrier exchange interactions in the DMSs give rise to large Zeeman spin splittings of the excitonic or band states and related giant magneto-optical Faraday rotation. In this paper, we compare structural and magneto-optical properties of Mn-doped semiconductor CdTe and ZnO nanoparticles prepared by different physical methods. Among physical techniques we have chosen ball milling or mechanical synthesis and pulsed laser ablation in liquids technique using combined targets. All the samples were characterized by electron microscopy, optical absorption, photoluminescence, and Faraday rotation spectroscopy. The magneto-optical spectra of nanoparticles exhibit peculiarities typical for bulk DMSs due to the strong spin-exchange interaction between band carriers and magnetic ions and simultaneously manifest some features because of confinement effects in low dimensional structures.

B.B I.20
17:45
Authors : Paola Tiberto1, Federica Celegato1, Gabriele Barrera1, 2, G. Aprile3, Luca Boarino1, G. Seguini4, Federico Ferrarese Lupi4, T. J. Giammaria4, Michele Perego4
Affiliations : 1.Electromagnetics, INRIM, Torino, Italy. 2. Università di Torino, Torino, Italy. 3. Università del Piemonte Orientale, Alessandria, Italy 4. MDM, IMM -­ CNR, Agrate Brianza, Italy.

Resume : Synthesis of nanopatterned magnetic materials offers advanced capabilities in tailoring material structures and opens up new opportunities for engineering innovative devices (i.e. electronic and biomedical). In the frame of magnetic materials, the most demanding application consists in fabricating high-density arrays for use in data storage and magnetic sensors for spintronics [1]. In the last decade, many routes for the reliable fabrication of magnetic nanostructures have been extensively investigated, including top-down lithography and bottom-up self-assembly processes. Conventional electron beam lithography (EBL) soon turned out to be limited by low-­speed and high costs while self-­assembling emerged as a viable and handy alternative technique for designing nanostructures over a wide area on magnetic thin films. The capability of soft materials such as block copolymers (BC) to form a rich variety of low-dimensional, uniform periodic patterns offers unique opportunities to develop large area nanometer scale features. The domain spacing typically depends on molecular weight, segment size, and the strength of interaction between the blocks. In this work, block-copolymer (BCP) – based lithography has been exploited to fabricate uniform, densely spaced nanometer – scaled on Ni80Fe20 and Co sputtered thin film with thickness ranging in the interval 10 - 30 nm. A Random Copolymer (RCP) brush layer was deposited on the Si substrate in order to obtain the surface neutralization. A PS-b-PMMA Block Copolymer (BCP) film was subsequently deposited on the RCP, obtaining cylindrical features perpendicularly oriented with respect to the substrate. In this way, a patterned nanostructure having cylindrical features has been realized. The self organization is promoted by means of a thermal annealing higher than the glass transition temperature of the BCP. The magnetic layer is then deposited by RF sputtering. A careful evaluation of the propagation effect of the nanometric pattern to the magnetic thin film has been performed with the aim to optimise nanostructures and preserve the magnetic properties of the continuous film. A systematic morphological study has been made by Scanning Electron (SEM) microscopy. Room-temperature magnetic behavior has been studied by magnetisation measurements by means of ultra-sensitive magnetometry measurements [2] following the hysteresis loop changes during all the step process.

B.B I.22
17:45
Authors : M.A.Osman 1, A.A.Othman 1, Waleed A. El-Said 2 , A.A.Abu-shely1 and Ahmed G.Abdel rahim1
Affiliations : 1 Physics Department, Faculty of Science, Assiut University. 2 Chemistry Department, Faculty of Science, Assiut University.

Resume : CdS nanoparticles were synthesized by co-precipitation method using Cadmium acetate (Cd (CH3COO)2) and sodium sulfide (Na2S) as ionic precursors. The samples were annealed in air for 3 h in steps of 100 ?C in the temperature range of 200 ?700 ?C to study the effect of annealing temperature (Ta) on the structural and optical properties of CdS nanoparticles and the UV photo-induced changes in the optical properties of the samples. Structural and optical properties were investigated using x-ray diffraction (XRD), UV-Vis absorption spectroscopy and fourier transform infrared (FTIR) spectroscopy. The increase of average crystallite size D from 2.67 to 23 nm as a result of annealing has been estimated frm the broadening of x-ray line. Substantial phase transition at Ta = 300 oC from as prepared Cubic CdS structure to CdS hexagonal structure and to CdSO3 monoclinic structure at Ta = 700. Analysis of the UV-Vis optical absorption spectra refers to the validity of direct allowed transition with remarkable decrease in the direct band gap E_g^opt from 3.3 to 2.4 eV at 700 oC with increasing Ta as a result of enhancement of crystallinity and increase in particle size which in turn leads to the reduction of quantum confinement effect. The observed phase transition and UV photo-induced changes were discussed in terms of the current models.

B.B I.23
17:45
Authors : A.G. Novikau, K.V. Kozadaev
Affiliations : Belarusian State University, 4 Nezavisimosti av., Minsk, Belarus

Resume : Cone-shaped metal nanoparticles (Ag, Au and Pt) were deposited on solid state silicon substrates by pulsed laser ablation at atmospheric pressure conditions. The structural properties and morphology of as-grown nanoparticles were investigated by atomic force microscopy and scanning electron microscopy with x-ray analysis. The nanocone diameter was found to vary significantly from 50 to 200 nm. The resonance absorption behaviour of optical transmittance spectra evidences excitation of surface plasmons on silver and gold nanocones. The dynamics of nanoparticle formation is discussed taking into account the vapor-plasma plume formation after intense nanosecond light irradiation of metal plates at atmospheric pressure and followed by vapor-plasma plume supersaturating. The effect of Raman scattering enhancement was estimated using R6G molecules solutions in the concentration range from 10-9 to 10-5 M.

B.B I.27
17:45
Authors : T.I. Verbitska, I.A. Vladymyrskyi, M.Iu. Verbitska, O.V. Fihurna, S.I. Sidorenko, E.P.Pavlova, Iu.N.Makogon,
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine y.makogon@kpi.ua

Resume : Influence of Cu intermediate layer thickness in nanoscaled Fe50Pt50(15nm)/Cu(x, nm)/Fe50Pt50(15nm) (where х = 0;7.5;15;30nm) film composition on SiO2(100 nm)/Si(001) substrates on the transformation of chemically disordered А1 phase into chemically ordered L10 phase at annealing in vacuum was investigated by methods of X-ray diffraction; atomic-force and magnetic-force microscopy; Rutherford backscattering, magnetic properties were measured with magneto-optic Kerra effect method; resistometry. It was established that during deposition the А1 phase forms in all films. The thickness of Cu layer effects on temperature of А1 L10 phase transformation onset in film compositions under investigation. The formation of L10 phase in film with small Cu interlayer thickness of 7.5nm occurs during annealing at 700?С. Increase in thickness of Cu interlayer to 15nm raises the ordering temperature by 100?С tо 800?С due to appearance of big compression stresses and deformations. Coercivity of film increases from 0.05 to 6.7 kOe. In film with big thickness Cu interlayer of 30nm after annealing at 800?С it is fixed formation of FeCuPt ternary compound but passing of ordering process with formation of L10 phase is not established. The authors would like to thank Prof. M. Albrecht and Dr. G. Beddies and workers from Chemnitz University of Technology (Germany) for sample preparation, assistance in conduction of investigations and discussion of results.

B.B I.30
17:45
Authors : 1:A.M.Niculescu , 1:C.T.Fleaca, 1:M.Dumitru , 1:M.Filipescu, 2:C.Nicolicescu, 3:E.Vasile, 1:I.Morjan, 1:M.Dinescu
Affiliations : 1National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor Str., 77125 Bucharest- Magurele, Romania 2 University of Craiova, Faculty of Mechanics, Department of Engineering and Management of the Technological Systems,Drobeta Turnu Severin, Romania 3 University POLITEHNICA of Bucharest, Faculty of Applied Chemistry and Material Science, Department of Oxide Materials and Nanomaterials, No. 1-7 Gh. Polizu Street, 011061 Bucharest, Romania

Resume : Tin oxide-based nanoparticles were obtained by glycine combustion technique starting from organometallic tetrabutyl-bis(acetyloxi) distanoxane precursor and rare earth nitrates of of Ce , Eu , La as dopants sources . The dopant concentration was controlled to obtain a Sn/La atomic ratio of 95/5. The reference powder (undoped SnO2) and the doped ones were dispersed in aqueous media together MWCNTs at different concentrations with the aid of a Na Carboxymethylcellulose (hydrophilic surfactant) using ultrasonication. Their hydrodynamic size distributions were evaluated by DLS (Dynamic Light Scattering). The water-based mixtures were frozen in liquid nitrogen and deposited using MAPLE (Matrix Assisted Pulsed Laser Evaporation) on silicon substrates. The resulted films were characterized by XRD, AFM, EDAX, DLS ,TGA. Their properties are discussed in relation with sensors application.

B.B I.34
17:45
Authors : Michał Gawełczyk, Paweł Machnikowski
Affiliations : Institute of Physics, Wrocław University of Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland

Resume : We model spin dynamics in a double quantum well (DQW) in the electric field, which enhances the tunneling of particles, and in a magnetic field causing spin precession. Considering optical pumping, we simulate the time resolved Kerr rotation signal. Studies of spin dynamics in neutral nanostructures are limited by fast exciton recombination. Doped structures are therefore commonly used, but, due to the lower quality of such materials and the intrinsic spin dephasing in the initialization of resident spins (affecting results of resonant spin amplification experiments), an undoped system with long living spins was needed. A DQW system with the electron-hole pair separation caused by carrier tunneling enhanced by the electric field is the answer. In our model, magnetic field impact is considered exactly, while the dissipative dynamics (relaxation, decoherence, tunneling, recombination) is described in the Markov limit in the master equation for the density matrix evolution. We model the pumping by the circularly polarized pulse and the linearly polarized probe pulse. The correspondence with experimental signal is obtained by dynamical variables such as spin polarization and coherences for each of QWs. We find that the extension of spin polarization lifetime depends mainly on the tunneling to recombination time ratio. The temperature and sample inhomogeneity impact is considered. Comparing the simulations with experimental data one may obtain dynamical parameters of the system.

B.B I.35
Start atSubject View AllNum.
09:30
Authors : Sebastian Glassner (1), Clemens Zeiner (1), Priyanka Periwal (2), Thierry Baron (2), Emmerich Bertagnolli (1) and Alois Lugstein (1)
Affiliations : (1) Institute of Solid State Electronics, Vienna University of Technology, Floragasse 7, 1040 Vienna, Austria (2) Laboratoire des Technologies de la Microélectronique (LTM), UMR 5129 CNRS-UJF, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble, France

Resume : The continuous advance in technology predicted by Moore's law can be mainly attributed to the excellent scalability of the metal oxide semiconductor field effect transistor. However, down-scaling faces an insurmountable limitation when characteristic lengths reach the sub-10 nm regime. The increased leakage at such a scale and the fundamental thermal limit of the subthreshold swing encourage research on new device geometries and transport mechanisms. Non-planar geometries like silicon nanowires are potential successors to conventional planar structures as they feature increased electrostatic control and further potential of miniaturisation as they are able to supress short channel effects. Alternative transport mechanisms like band-to-band tunnelling or impact ionisation enable faster switching and decreased leakage. Similarly, Schottky barrier tunnelling is expected to beneficially affect the thermal dependency of the subthreshold swing. The combined capabilities of both a non-planar design and non-conventional carrier injection mechanisms are subject to recent scientific investigations. In the scope of this work, experiments with silicon nanowires that feature a significant axial n-type/intrinsic doping junction have been conducted. The nanowires with diameters ranging from 60 to 120 nm were synthesised via the vapour-liquid-solid method using gold colloids, and the doping profile was obtained via in-situ doping with phosphine. The nanowires were removed from their growth substrate and drop-casted onto a silicon substrate with a 100 nm layer of aluminium oxide. A heterostructural device design was achieved by employing nickel-silicide as a source contact material at the intrinsic side of the nanowire. This allows for the fabrication of a self-aligned Schottky contact after the evaporation of nickel in an annealing step at a low thermal budget of 510°C. The one-dimensional nature of the silicide contact is markedly beneficial concerning the electrostatic control of the intrinsic channel close to the contact. An ohmic contact was fabricated at the highly doped drain side also by evaporating nickel. In a subsequent step the nanowires were passivated with a 10 nm layer of aluminium oxide. A reconfigurable device is shown which allows to control whether the device acts as p- or n-type transistor. The functionality of the device is based on a dual-gate structure namely the contact-gate just in the vicinity of the silicide-to-silicon junction, and the channel-gate which overlaps the contact-gate and the doping junction. With this approach not only the type but also the carrier injection mode can be altered by applying a suitable voltage at the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunnelling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 10^4 is found. As the device operates in forward bias, a non-conventional tunnelling transistor is identified, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type configurations are distinguishable. On the one hand, the carrier injection is dominated by thermionic emission in forward bias. The resulting device operates as a conventional nanowire transistor and exhibits a subthreshold swing of 216 mV/dec at the highest ON/OFF ratio of up to 10^7. On the other hand, in reverse bias a Schottky tunnelling mechanism allows for a normally-off n-type characteristic with a moderate subthreshold swing of 813 mV/dec at an ON/OFF ratio of up to 10^4.

B.6.2
09:45
Authors : V. Brouzet1,2, B. Salem1, P. Periwal1, T. Baron1, F. Bassani1, P. Gentile3, G. Ghibaudo2
Affiliations : 1 Univ. Grenoble Alpes, LTM, F-38000 Grenoble, France CNRS, LTM, F-38000 Grenoble, France 2Univ. Grenoble Alpes3bis, IMEP-LAHC, F-38000 Grenoble, France CNRS, IMEP-LAHC, F-38000 Grenoble, France 3 CEA/INAC/SiNaPS 17 Rue des Martyrs F-38054 Grenoble-France

Resume : Tunnel Field-Effect Transistor (TFET) offers the potential to overcome the subthreshold swing (SS) thermal limit of 60mV/dec at 300K inherent to metal-oxide-semiconductor field-effect transistors (MOSFET), since TFET conduction is governed by band-to-band tunnelling (BTBT) rather than thermionic injection. Moreover, the use of nanowire as channel of transistor is an adequate technological solution enabling a high integrated device density and a good electrostatic control [1]. In addition, heterostructure TFET with small band gap material in the source region, such as SiGe [2], is one of the most promising candidates, with theoretically expected on-state current and subthreshold swing improved as compared to Si homostructure TFET. In this context, we have integrated Si/Si/SiGe heterostructure nanowires with an in situ p(Si)-i(Si)-n(SiGe) doping profile on TFET device. These nanowires were elaborated by Chemical-Vapor-Deposition using Vapor-Liquid-Solid mechanism with gold as catalyst. Thanks to the reduction of the band gap of the source material, device optimisation resulted in increased band-to-band tunnelling with an ION current of about 3 µA/µm, an ION/IOFF ratio up to 105 and an average SS less than 135mV/decade. Electrical measurements as a function of temperature have also been performed and will be presented. [1] A.M. Ionescu et al., Nature, vol. 479, pp.329-337, (2011). [2] A.S.Verhulst et al., Appl. Phys. Lett. 104, 064514, (2008).

B.6.3
10:00
Authors : R. A. Puglisi, S. Caccamo, C. Garozzo, S. Di Franco, M. Italia, A. La Magna.
Affiliations : Consiglio Nazionale delle Ricerche – Istituto per la Microelettronica e Microsistemi, Ottava Strada 5, Zona Industriale, 95121 CATANIA

Resume : Doping Si nanostructures by using standard methods presents some critical issues like conformality, control on dopant distribution and reduced structural damage. An effective method to dope nano-patterned Si and create controlled and conformal junction profiles has been recently proposed in literature [Nature Mater. 7, 62 (2008), Mat. Sci. & Eng. B 178 (2013) 686 10.1016/j.mseb.2012.11.019, Phys. Stat. Sol. A 210(8) (2013) 1564 10.1002/pssa.201200949]. It consists in forming a layer of dopant containing molecules by immersion of the samples in a chemical bath and successive deposition of a cap layer and annealing, during which the dopant atom is released by the molecule and diffuses into the Si substrate or in the nanostructures. Here we present a systematic study of this doping technique by varying the important processing parameters, and demonstrate that the method allows for the precise control of the crucial junction's features (i.e. dopant dose and junction's depth) without structural damage. We applied the doping procedure to arrays of nanopores obtained by diblock-copolymer lithography. Due to their optical absorption properties the nanopores provide a light trapping effect on the surface of the solar cell. The doped layers are used as active materials in solar cells prototypes based on the nanostructured Si. The results show improved photoconversion performance respect to the reference flat diodes and pave the way to create efficient nanostructured cells.

B.6.4
11:45
Authors : S. Gutsch (1), H. Gnaser (2), J. Goettlicher (3), R. Steininger (3), D. Hiller (1), M. Zacharias (1)
Affiliations : (1) IMTEK, University of Freiburg, Germany; (2) Kaiserslautern University of Technology, Germany; (3) ANKA, Karlsruhe Institute of Technology, Germany

Resume : A lack of consensus persists regarding the electronic impurity doping of ultrasmall Silicon nanocrystals in the range from 2 to 5 nm in a dielectric host matrix and the efficiency to provide free electrons [1,2]. Here we apply complementary 3D atomprobe [3] and synchrotron X-ray absorption spectroscopy to study phosphorus (P) incorporation into silicon nanocrystals embedded in SiO2. It is demonstrated that a large amount of P is trapped at the Si/SiO2 interface, although also significant amounts of P are proven to be incorporated into the nanocrystals. However, optical and electrical measurements indicate that the vast majority of these introduced P atoms is inactive suggesting the absence of significant amounts of substitutional P sites. In addition the dopant activation energy is found to be too high to be ionized at room temperature. Contrasting numerous literature reports, it is concluded that P does not appear to be a suitable dopant for Si nanocrystals. [1] Stegner et al., Phys. Rev. B 80, 165326 (2009) [2] Gutsch et al., Appl. Phys. Lett. 100, 233115 (2012) [3] Gnaser et al., J. Appl. Phys. 115, 034304 (2014)

B.7.3
12:00
Authors : J. Laube, S. Gutsch, D. Hiller, M. Zacharias
Affiliations : Laboratory for Nanotechnology, Department of Microsystems Engineering - IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110 Freiburg im Breisgau, Germany

Resume : A monosilane (SiH4) and oxygen (O2) based plasma-enhanced chemical vapor deposition process (PECVD) for the growth of silicon-rich oxide / silicon dioxide superlattices [1] was developed. In contrast to the conventional nitrous oxide (N2O) based oxynitride-process [2], we achieved thereby PECVD-grown size-controlled silicon nanocrystals in pure, N-free silicon dioxide matrix. We present a detailed study based on optical (PL) and electrical (C-V, I-V) measurements that reveal the different properties of nominally identical Si nanocrystals in oxynitride and N-free oxide matrix. Most strikingly we find negligible differences in the optical performance (PL quantum yield), whereas substantial differences in the current transport and transient charging behaviour persist. The role of the pure oxide vs. oxinitride matrix on the properties of Si quantum dots is discussed in the context of potential applications in photovoltaics and optoelectronics. [1] M. Zacharias et al., APL 80, 2002 [2] A.M. Hartel et al., TSF 520, 2011 [3] S. Gutsch et al., JAP 113, 2013

B.7.4
12:15
Authors : Daniel Hiller, Anastasia Zelenina, Sebastian Gutsch, Margit Zacharias
Affiliations : IMTEK, Faculty of Engineering, University of Freiburg, Freiburg, Germany

Resume : We present a systematic study of the photoluminescence (PL) mechanisms of size controlled Si nanocrystals (Si NCs) embedded in silicon nitride matrix (Si3N4) [1]. In contrast to numerous papers we found manifold evidence that the origin of PL cannot be related to quantum confined excitons in Si quantum dots. The true PL mechanism is discussed in the context of band tail states and radiative defects. Our argumentation is based on the following observations: - Si3N4 reference samples show similar PL emission as Si NC samples; - the PL decay is 10^5 times faster than normal for Si NCs [2]; - the PL peak shift with NC size is identified as optical interference artifact via PL transfer matrix simulations considering Fabry-Pérot resonances [3]; - PL-excitation measurements prove an identical excitation mechanism irrespective of the presence of Si NCs. Using ESR data of Si/Si3N4 interface defect densities, we calculate infinitesimal probabilities to find defect free and luminescent Si NCs. Also hole trapping and PL quenching Si3N4-VB-tail states are discussed. In terms of application (Si NC based all-Si tandem solar cell [4]), Si3N4 was formerly favored due to its band offsets compared to SiO2 and SiC. However, our results suggest that it has to be rather classified as “subprime” matrix material. [1] Hiller et al., JAP 115, 204301 (2014) [2] Hartel et al., PRB 87, 035428 (2013) [3] Dyakov et al., APL 100, 061908 (2012) [4] Green, Third Generation Photovoltaics (Springer, 2003)

B.7.5
15:00
Authors : M.C. Giordano, C.Martella and F. Buatier de Mongeot
Affiliations : Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, I-16146 Genova, Italy

Resume : Noble metal nanoclusters are confined by grazing angle Au deposition on rippled glass templates and polymer nanosphere(200-400nm diameter) Photonic Crystals. The nanosphere templates are prepared by soft lithography, while the rippled glasses by a self-organised approach exploiting Ion Beam Sputtering(IBS).Metal deposition on the ripples titled facets allows the confinement of highly anisotropic 1D arrays of metal nanoclusters, characterised by a strong optical dichroism. At low metal doses, as a consequence of Localised Plasmon Resonances (LSPRs) excitation, well-isolated nanoclusters exhibit dichroic optical properties both in the linear and non-linear regime[1]. Increasing the metal dose deposited on rippled templates we are able to form arrays of connected Nanowires which are endowed with elevated electrical conductivity and high optical transparency. Such properties open the possibility to exploit these samples as semi-transparent plasmonic nanoelectrodes, in analogy to the Au nanowire arrays prepared by direct IBS of a polycrystalline metallic film[2,3]. Instead, on the closed-packed nanosphere layer, Au evaporation leads to ordered 2D arrays of isolated nanostructures, shaped as half-moon crescents[4] and characterized by anisotropic optical response due to the excitation of LSPRs[5]. [1]A.Belardini et al. Phys.Rev.Lett, 2011 [2]D.Chiappe et al. Small, 2013 [3]B.Fazio et al. ACSNano 2011 [4]V.Robbiano et al. Adv.Opt.Mater. 2013 [5]A.Belardini et al. Adv.Opt.Mater. 2014

B.8.4
16:15
Authors : T. Riedl 1, A. Kovács 2, D. Meertens 2, J.K.N. Lindner 1
Affiliations : 1 University of Paderborn, Department of Physics, Warburger Str. 100, 33098 Paderborn, Germany; 2 Ernst-Ruska Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, 52425 Jülich, Germany

Resume : III-V semiconductor nanowires or pillars have attracted considerable attention due to their outstanding properties such as large surface-to-volume ratio, tunable band gap, high carrier mobility, carrier confinement and enhanced elastic relaxation of misfit strains in heterostructures. Thus, they have a great potential for realizing advanced electronic and optoelectronic devices e.g. high-performance field-effect transistors, light-emitting diodes, photovoltaic cells [1] or sensors. Owing to its direct bandgap GaAs represents an important III-V semiconductor for optoelectronic applications. In the present contribution we analyze the structure and surface chemistry of ultra-thin (diameter in the range of 20 to 50 nm) vertical-sidewall GaAs (111) nanopillars. As demonstrated in a previous paper the pillars are fabricated by deposition of nanosphere lithographically defined Ni mask particles followed by selective SiCl4 reactive ion etching of the GaAs substrate [2]. We use transmission electron microscopy (TEM) imaging to reveal the crystalline structure of the pillars, and analytic TEM to identify conditions allowing for a complete mask removal by hydrofluoric wet chemical etching. References [1] J.A. Czaban, D.A. Thompson, R.R. LaPierre, Nano Lett. 9 (2009) 148. [2] T. Riedl, J.K.N. Lindner, submitted (2014).

B.9.2
16:45
Authors : D. Nunes, T.R. Calmeiro, J.V. Pinto, S. Nandy, A. Pimentel, A. Kiazadeh1, P. Barquinha, P.A. Carvalho, E. Fortunato, R.Martins
Affiliations : Departamento de Ciência dos Materiais, CENIMAT/I3N, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa and CEMOP-UNINOVA, 2829-516 Caparica, Portugal ICEMS, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Resume : Copper-based materials are widely employed with applications ranging from nano-optoelectronics to gas sensors. However, enhanced performance is demanded and in general fine-grained materials result in property improvements. The present work reports the characterization of Cu nanowires, as well as its further oxidation through microwave radiation or furnace annealing in atmospheric conditions resulting in Cu2O and CuO nanowires, respectively. The nanowires were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). An extensive study of localized charge transport mechanism with simultaneous surface topography of different Cu-based nanowires has been shown by atomic force microscopy (AFM) studies using metal coated conducting probes. Remarkable structural differences were detected between both oxidation processes: nanowires annealed in air consisted of nanocrystalline aggregates displaying hollow structure, whereas microwave radiation resulted in bulk twinned nanowires.

B.9.4
17:00
Authors : X. Han, H. Morgan Stewart, S. A. Shevlin, C. R. A. Catlow, and Z.-X. Guo
Affiliations : Department of Chemistry, University College London, Gower St, London, United Kingdom

Resume : One of the most critical and challenging issues facing the electronics industry is the development of alternatives to silicon-based materials so as to enable large improvement in device performance. Considerable efforts have been devoted to 2D materials, such as graphene, which despite promising charge transport properties is unable to function as a switch in transistor devices due to the lack of an intrinsic bandgap. The recent exfoliation of black phosphorous, which consists of weakly stacked layers of a quasi-planar corrugated half-honeycomb structure, dubbed phosphorene, has garnered huge experimental and theoretical interest due to its relatively large and direct band gap and good charge carrier mobilities, We have used Density Functional Theory to investigate the properties of passivated phosphorene nanoribbons, denoted armchair (a-PNR), diagonal (d-PNR) and zigzag (z-PNR). We found that z-PNRs demonstrate the greatest quantum size effect, tuning the band-gap from 1.4 to 2.6 eV when the width is reduced from 26 to 6 ?. Strain effectively tunes charge carrier transport, in particular leading to a sudden increase in electron effective mass around 8% strain for a-PNRs or hole effective mass around 3% strain in z-PNRs ? differentiating the (m_h^*/m_e^*) ratio by two orders of magnitude in each case. Straining of d-PNRs results in a direct to indirect band-gap transition at either ?7% or 5% strain, and therein creates degenerate energy valleys, with potential applications for valleytronic applications. Finally, we present results on the optical properties of phosphorene-derived nanostructures, with a particular focus on the exciton dynamics and plasmon resonance.

B.9.5
17:15
Authors : Bong Kyun Kang, Hyeong Dae Lim, Sung Ryul Mang, Keun Man Song, and Dae Ho Yoon
Affiliations : Sungkyunkwan University

Resume : In recent years, metal-oxide semiconductor nanomaterials such as nanotubes, wires, particles and hollow nanostructures are attractive candidates as active elements for advanced nanoscale devices due to their unique electronic and optical properties, low effective density, high specific surface area, and shell permeability that can be of importance to many areas of technology. Most of the metal-oxide semiconductor hollow nanostructures were prepared using template-based fabrication methods. Especially, fabrication using carbon spheres as the templates offer more advantages when compared with other templates. Recently, ZnO and Ga2O3 nanowires were used as hard templates to fabricate a ZnGa2O4 nanotubes, in which synthesized ZnO@Ga2O3 and Ga2O3@ZnO core-shell nanowires were followed by solid state reaction at high temperatures. Highly uniformed single crystalline ZnGa2O4 hollow nanostructures with cubic spinel structure were successfully fabricated, in which synthesized carbon@Ga(OH)CO3@Zn(OH)2 core-sell-shell structures with carbon spheres as the templates and then calcined process. We report the synthesis and characterization of ZnGa2O4 hollow nanostructures under controlled several experiment condition

B.9.6
17:30
Authors : Girel K. V., Niauzorau S. A., Sharstniou A. I, Girel A. I., Bondarenko V. P.
Affiliations : Department of Micro- and Nanoelectronics, BSUIR, Minsk, Belarus

Resume : In this work, we present the results of study of porous silicon (PS) fabricated by two-step metal-assisted chemical etching. This method is used to form PS with different structures, including Si nanowires. On the first step, Ag nanoparticles (NPs) were formed by immersion deposition on the surface of Si wafer. Ag was selected because of its high catalytic activity. Variation of AgNO3 concentration in the solution for Ag deposition from 1 to 3 mM, immersion time from 5 to 60 min and type of Si wafer allowed to form Ag NPs with dimensions from 30 to 100 nm. On the second step, Si wafer with Ag NPs was immersed in aqueous solution of HF and H2O2 for 5 – 120 min. The concentrations of HF and H2O2 varied in the ranges of 4,5 – 9,5 M and 0,3 – 3 M, respectively. The morphology and structure of the obtained samples were studied by SEM and XRD analysis. It was shown that PS can have ordered or disordered structure depending on the formation conditions. Thickness of PS varied from 5 to 15 µm. Porosity of ordered and disordered PS with thickness of 10 µm was about 60 - 65 % and 65 - 75 %, respectively. Possible application of such PS in surface enhanced Raman spectroscopy for biomedical sensing is discussed. This research was financially supported by Belarussian Republican foundation for fundamental research in the range of Grant T13M-161.

B.B II.2
17:30
Authors : Anna Duzynska, Jarosław Judek, Mariusz Zdrojek
Affiliations : Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw, Poland

Resume : We report first studies on temperature dependent (70-450K) Raman spectra of single-walled carbon nanotubes (SWCNTs), high density thin films (40nm). We show that the position of the main Raman mode (G) is soften as the temperature increases. Both phonon shifts and width exhibits a nonlinear behavior in the range of 70-270 K. This effect is explained by the optical phonon decay into two acoustic phonons. The first-order temperature coefficient (χT) was calculated to be -0.02 cm-1/K, which is lower than for any other CNTs. Importantly, we found that laser-induced local temperature change versus global temperature shows nonlinear trend with the minimum at 270 K. Our results give a new contribution to the understanding of the thermal properties of carbon nanotube thin films that could find application e.g. in photovoltaic or thermoelectric devices.

B.B II.4
17:30
Authors : D. Drude, K. Brassat, Ch. Brodehl, T. Riedl, J. K. N. Lindner
Affiliations : Department of Physics, University of Paderborn, Paderborn, Germany; Center for Optoelectronics and Photonics CeOPP, University of Paderborn, Paderborn, Germany

Resume : Nanosphere lithography (NSL) is attracting increasing interest as a low cost method for the nanopatterning of large area substrates. First colloidal nanoparticle arrays are deposited on planar surfaces by a self-assembly process. The hexagonal particle layers act as shadow mask for subsequent site-controlled surface modifications such as material deposition or removal [1]. Highly regular surface patterns are frequently required for optoelectronic and photonic applications, but “crystal defects” in the self-organized mask typically limit the pattern regularity. We use the doctor blade technique based on convective self-assembly to form monolayers of polystyrene beads on silicon substrates from aqueous suspensions. In this method the bead arrangement is influenced by various parameters such as particle concentration, particle size distribution, blade velocity relative to the substrate and temperature. In order to determine the mask quality a computer program based on Delaunay triangulation was developed which analyses automatically visible light microscopy or scanning electron microscopy images. By this it is possible to measure the areal density of typical mask defects such as grain boundaries, dislocations and point defects. The local sphere coordination can be determined at any position of the mask. Thus, optimum mask deposition conditions can be identified to minimize the density of mask defects. [1] J. C. Hulteen and R. P. van Duyne, J. Vac. Sci. Technol. A 13 (1995)

B.B II.14
17:30
Authors : Ch. Brodehl, S. Greulich-Weber, J. K. N. Lindner
Affiliations : Department of Physics, University of Paderborn, Paderborn, Germany Center for Optoelectronics and Photonics CeOPP, University of Paderborn, Paderborn, Germany

Resume : Nanosphere lithography (NSL) is a powerful low-cost technique to pattern large area planar substrate surfaces with 2D arrays of nanoobjects. It is based on the self-organization of nanobeads from a colloidal suspension forming a hexagonally close packed mono- or bilayer upon controlled drying of the suspension. The free interstices between neighboring beads are used as mask openings through which material can be either deposited on or removed from the substrate. Typically the nanopatterns on the substrate surface exhibit the triangular or hexagonal shape (for mono- or bilayers) of the projected mask openings. Here we demonstrate that using double-angle resolved deposition through a modified mask a large variety of new motives can be reproducibly formed at each mask opening. By thermal annealing of polystyrene nanosphere masks, the mask openings are contracted to reduced diameter circular apertures located in the equator plain of the spheres. Using a home-built electron beam deposition system with two-axis sample goniometer (inclination ϴ, azimuth φ) allows us to write complex motives at each mask opening in parallel. A ray trace type of algorithm was developed to calculate the route ϴ(t),φ(t) to obtain any desired pattern. Mask clogging effects can be taken into account to tailor the three dimensional shape of nanoobjects. Atomic force microscopy is used to compare the shape of 200 nm diameter optical split ring resonators and other nanoobjects with their layouts.

B.B II.17
17:30
Authors : T.I. Verbitska, I.A. Vladymyrskyi, O.V. Fihurna, S.I. Sidorenko, E.P.Pavlova, Iu.N.Makogon
Affiliations : Kyiv Polytechnic Institute, National Technical University of Ukraine, 03056, Prospect Peremogy 37, Kyiv, Ukraine

Resume : Influence of Cu intermediate layer thickness in nanoscaled Fe50Pt50(15nm)/Cu(x, nm)/Fe50Pt50(15nm) (where х = 0;7.5;15;30nm) film composition on SiO2(100 nm)/Si(001) substrates on the transformation of chemically disordered А1 phase into chemically ordered L10 phase at annealing in vacuum was investigated by methods of X-ray diffraction; atomic-force and magnetic-force microscopy; Rutherford backscattering, magnetic properties were measured with magneto-optic Kerra effect method; resistometry. It was established that during deposition the А1 phase forms in all films. The thickness of Cu layer effects on temperature of А1 L10 phase transformation onset in film compositions under investigation. The formation of L10 phase in film with small Cu interlayer thickness of 7.5nm occurs during annealing at 700?С. Increase in thickness of Cu interlayer to 15nm raises the ordering temperature by 100?С tо 800?С due to appearance of big compression stresses and deformations. Coercivity of film increases from 0.05 to 6.7 kOe. In film with big thickness Cu interlayer of 30nm after annealing at 800?С it is fixed formation of FeCuPt ternary compound but passing of ordering process with formation of L10 phase is not established. The authors would like to thank Prof. M. Albrecht and Dr. G. Beddies and workers from Chemnitz University of Technology (Germany) for sample preparation, assistance in conduction of investigations and discussion of results.

B.B II.18
17:30
Authors : Ho-Kyun Jang, Jun Eon Jin, Pil Soo Kang, Jun Hee Choi, Do-Hyun Kim*, Gyu Tae Kim*
Affiliations : School of Electrical Engineering, Korea University, Seoul, 136-701, Korea

Resume : By the discovery of CNT, it has been revealed that CNT has excellent electrical characteristics. Depending on its chirality, CNT can be classified into metallic and semiconducting one and is applied to various fields. In most cases, CNT is used in the form of networks because an individual CNT is hard to be controlled and unsuitable for further processes. The presence of electrical path is crucial when CNT is used in the form of networks. And, percolation theory can be useful to analyze it systematically. Although percolation theory has been applied to diverse CNT networks, theoretical and experimental works considered only the case that both metallic and semiconducting CNT co-exist. Recently, due to the advance of CNT separation, it is available to use highly pure metallic or semiconducting CNT. In spite of this situation, less effort was given to study electrical percolation threshold of semiconducting or metallic CNT networks. In this work, we investigated the percolation threshold of networks required in constituting electrical paths by using semiconducting single-walled carbon nanotube (SWCNT) on field-effect transistor (FET). By theoretical calculation, we obtained the relationship between density of semiconducting SWCNT and percolation probability by changing the channel length defined by source-drain electrodes of FET.

B.B II.19
17:30
Authors : Vorobets H.I., Vorobets M.M.
Affiliations : Yuriy Fedkovych Chernivtsi National University

Resume : Based on the results of experimental studies using scanning electron microscopy, electron and electron-probe microanalysis of structural and phase composition, and also computing modeling of the porous silicon layer formed by anodization on different ways treatment Si-wafer surface, its electronic and optical properties of the proposed generalized model of the peculiarities of the finishing chemical treatment (FCT) on the formation and physical and chemical properties of nanostructured porous silicon. Pretreatment of HNO3: HF: CN3COOH = 5:3:3 when creating Si-structures used as a polishing etching. During FCT in ammoniac-peroxide (AmPS) and the acid-peroxide solution (AcPS) in addition to effectively clean the surface of organic and inorganic impurities formed surface hydride (-Si-H), hydroxide (-Si-OH) or oxide layers (-Si -SixOy,-Si-SiO2). The surface layer may have a complex (multi-layered) structure at successive stages of the application FCT - AmPS and AcPS. The conditions and methods of FCT, in which the layers of macro-, micro-or mezoporous silicon are preferably formed are proposed. For samples p-Si is optimal anode current density between 50 and 70 mA/sm2. Indirectly finishing chemical treatment affects the electronic and optical properties of structures based on porous silicon. Oxidation of nanostructured layer of the porous Si and the presence of carbon leads to the formation of structures of nc-Si-SiO2-c-Si and nc-SihSu-SiO2-c-Si with a system of quantum dots in dielectric SiO2. As a result, there are quantum size effects, which manifest themselves in the form of resonance tunneling and hopping diffusion-drift mechanism of charge transfer in the detector structures with Schottky barrier Au-pc-p-Si-Cu and photoluminescence bands of nc-Si-SiO2 and nc-SihSu-SiO2 in the visible wavelength range. The direct impact of the method of finishing chemical treatment on the optical properties caused by the formation nanocrystals nc-Si and nc-Si(x)C(y) with different sizes. In the photoluminescence spectra is evident shift of the main emission band in the long-or short-wave region.

B.B II.20
17:30
Authors : Cezary Czosnek1a*, Mariusz Drygaś1a, Mirosław M. Bućko1b, Jerzy F. Janik1a
Affiliations : 1AGH University of Science and Technology, aFaculty of Energy and Fuels, bFaculty of Materials Science and Ceramics; Al. Mickiewicza 30, 30-059 Kraków, Poland *czosnek@agh.edu.pl

Resume : Due to many advantageous properties of nanosized silicon carbide SiC, there has been ever growing interest in its improved and affordable synthesis. In this regard, there are several routes known to produce nano-SiC materials. In the most popular and, arguably, the oldest method SiC is produced from silica/coke mixtures by electric heating. In that route, large microcrystals of α-SiC are obtained which can, subsequently, be crushed to grains of smaller sizes. Herein, we present the results of a study on the preparation of nanosized β-SiC by a two-stage pyrolysis process of several weeds containing native silica incorporated in organic parts of the plants. In the first stage of pyrolysis, the biomass was deprived of volatiles to yield a solid carbonizate composed, mostly, of silica and carbon. In the follow-up heat treatment at 1650 C under neutral gas atmosphere, silicon carbide in a composite system with an excess free carbon was produced due to carbothermal reduction of silica. All products were investigated with powder XRD and FT-IR spectroscopy supplemented with scanning electron microscopy SEM. The products were shown to be composite nanopowders made of SiC and free/excess C. By mild oxidation of excess carbon, it was possible to obtain pure bio-originated nanosized β-SiC powders. Acknowledgment. This work was supported by AGH University of Science and Technology Grant No. 11.11.210.213.

B.B II.27
17:30
Authors : G. P. Dimitrakopulos1, J. Kioseoglou1, N. Florini1, Ph. Komninou1, T. Walther2, K. Moratis3, Z. Hatzopoulos3, N. T. Pelekanos3, Th. Kehagias1
Affiliations : 1 Physics Department, Aristotle University of Thessaloniki, GR-54124, Thessaloniki, Greece; 2 Department of Electronic and Electrical Engineering, University of Sheffield, Mappin St, Sheffield S1 3JD, UK; 3 Materials Science & Technology and Physics Departments, University of Crete and IESL/FORTH, GR-71003 Heraklion, Greece

Resume : Core-shell GaAs/AlGaAs nanowires (NWs) for photovoltaic and photonic applications were grown on Si(111) by plasma assisted molecular beam epitaxy (PAMBE) via the vapor-liquid-solid mechanism, using Ga droplets as a catalyst. First, GaAs NWs were grown and then, growth continued adjusting the fluxes of Al, Ga, and As, to form the AlGaAs shell surrounding the initial GaAs core. The nanostructure of core-shell NWs was explored by high-resolution and scanning transmission electron microscopy (HRTEM-STEM). NWs are zinc-blende (ZB) single crystals grown epitaxially along the [111] direction, despite the presence of the thin amorphous native oxide. They originate on small heavily twinned GaAs crystals and then, they grow by a constant sequence of (111) mirror twins. The core-shell structure of the NWs was revealed by both diffraction contrast TEM and annular dark-field (ADF) STEM imaging, showing that the AlGaAs shell occupies at least one half of the projected diameter of the NWs, ranging from 80 nm to 200 nm. The Al content of the shell was estimated at ~35% by energy dispersive X-ray (EDX) analysis. Finally, molecular dynamics (MD) simulations of plan-view slices of the NWs were applied to calculate the variation of the energy, the stress tensors, the displacement field and the strain components of the core-shell configuration. Acknowledgments: Research co-financed by the EU (ESF) and Greek national funds - Research Funding Program: ARISTEIA II, project NILES.

B.B II.28
17:30
Authors : Katia Sparnacci (A), Diego Antonioli (A), Valentina Gianotti (A), Federica Campo (A), Michele Laus (A), Federico Ferrarese Lupi (B), Tommaso Jacopo Giammaria (B), Monica Ceresoli (B), Gabriele Seguini (B), Michele Perego (B), Luca Boarino (C), Natascia DeLeo (C), Giulia Aprile (C)
Affiliations : (A) Dipartimento di Scienze e Innovazione Tecnologica (DIST), Università del Piemonte Orientale “A. Avogadro”, Viale T. Michel 11, 15121Alessandria, Italy INSTM Udr Alessandria; (B) Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20846 Agrate Brianza (MB), Italy; (C) Nano Facility Piemonte, Electromagnerism Division, Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, Torino, 10135, Italy

Resume : Tailoring surface energies is the key factor to control the orientation of nanoscopic structures in block copolymer (BCP) thin films. When the BCP thin film is confined between substrate/polymer and air/polymer interfaces, preferential wetting of either the air or substrate interfaces by one of the blocks leads to a parallel orientation of the microdomain morphology with respect to these interfaces. One of the most popular methods to control the BCP morphology orientation is the chemical modification of substrate surface by hydroxyl terminated random copolymers composed of the same monomers as the BCP. As the random copolymer chemical composition can be precisely controlled, a fine-tuning of the surface characteristics can be obtained. The grafting occurs by a thermally activated reaction of HO-Si substrates with the hydroxyl groups of the functional (co)polymers. In this work, we prepared a series of hydroxyl terminated poly(styrene-r-methylmethacrylate) random copolymers with different molar masses, ranging from 1500 to 70000 g/mol. Then the Rapid Thermal Processing (RTP) technology was employed to perform flash grafting reactions of the random copolymers to the activated silicon wafer surface. The use of RTP technology allows the grafting reaction to be obtained on the timescale of few seconds, thus opening new possibilities in several fields of surfaces and interfaces in science and technology.

B.B II.29
17:30
Authors : C. Martella*, C. Mennucci*, M. C. Giordano*, D. Chiappe*, I. Usatii°, L. V. Mercaldo°,P. Delli Veneri° and F. Buatier de Mongeot*
Affiliations : *Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, I-16146 Genova, Italy °ENEA Portici Research Center, Piazzale E. Fermi, I-80055, Portici (NA), Italy

Resume : Here we report on the optical functionalization of glass and semiconductor (Si and GaAs) substrates in view of light trapping and photon harvesting in photovoltaic devices [1-2]. Defocused Ion Beam Sputtering, assisted by a sacrificial self-organised Au stencil mask, is exploited in order to project in the underlying substrate a pattern of high aspect ratio nanoscale features. We describe the formation of a quasi-periodic array of 1-D nanostructures with RMS roughness in the 80-130 nm range as a function of the total ion dose (vertical dynamic range roughly 500 nm). The characteristic lateral size of the nanostructures, estimated from the height-height correlation function, is in the range of 200 nm. The tailored optical properties of the substrates are characterised in terms of total reflectivity and haze by means of integrating sphere measurements as a function of the morphological modification at increasing ion fluence. A broad-band anti-reflection effect (10-20% reduction with respect to a flat reference) is found in the VIS-NIR range. At the same time the patterned substrates have shown enhanced broadband light scattering functionalities as quantitatively highlighted by the Haze functions which can be tailored in the 30%-60% range[1-2].The first encouraging results demonstrate that a:Si solar cells grown on patterned glasses exhibit a 15% relative enhancement in photocurrent due to light trapping. [1] [2] C.Martella et al.Nanotechnology 2013, J. Appl. Phys. 2014.

B.B II.30
17:30
Authors : Denys Savchenko, Eugene Paschenko, Olga Lazhevskaya, Andrei Chernenko
Affiliations : V. Bakul Institute for Superhard Materials NAS of Ukraine; V. Bakul Institute for Superhard Materials NAS of Ukraine; V. Bakul Institute for Superhard Materials NAS of Ukraine; V. Bakul Institute for Superhard Materials NAS of Ukraine

Resume : Hybrid polymeric materials are the perspective direction of the modern material science. Such materials consist of nano-scale organic and inorganic fragments. They have advantages of both material types due to the such feature. The mechanical properties investigation of them can be the purposeful development basis of instrumental and functional materials. The free volume of hybrid polymers play the particular role in their mechanical properties. There is a possibility to regulate the parameters of the free volume. In turn changes of these parameters can influence on mechanical properties of hybrid polymers. Metal-containing polyphenyles were used as hybrid polymers. The free volume of them was studied. In particular, free volume fraction was investigated. It was studied with the help of mass-spectrometry data. The influence of the free-volume fraction on the Young modulus, wear resistant, and other properties were confirmed. The mechanism of the such influence was proposed. There is an ability to control free volume fraction by filler introduction, polymerization temperature and pressure. Optimal parameters of the free volume fraction size were found.

B.B II.35
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14:45
Authors : E. L. Gurevich, S. V. Gurevich
Affiliations : Chair of Applied Laser Technologies, Ruhr-University of Bochum, Germany; Institute for Theoretical Physics, University of Muenster, Germany

Resume : Self-organized nanostructures appear on metal surfaces exposed to ultra-short laser pulses. Periodic stripes (also referred to as LIPSS), cells and localized structures with characteristic lengths in the range from 100s to 1000 nm can be observed. Here we discuss the characteristics of the self-organized patterns and the experimental possibilities, how these characteristics can be controlled. New physical model of the periodic pattern formation based on the commonly-used two-temperature model (TTM) is proposed. It is shown that the temperature profile on the surface may be unstable with respect to a periodic perturbation, which can give rise to the periodic modulation of the height profile. Characteristic wavelength of the instability and the growth rate of the periodic pattern are estimated from the material constants of the target. Possible influence of hydrodynamic instabilities induced by the periodic temperature profile modulation on the surface are discussed.

B.11.3
15:15
Authors : E. Chubenko, S. Redko, A. Dolgiy, V. Bondarenko
Affiliations : Belarusian State University of Informatics and Radioelectronics, P. Brovka str. 6, Minsk 220013, Belarus

Resume : Porous silicon (PS) has proved itself as a versatile template for a manufacturing nanostructure arrays and nanocomposites. However PS lacks reproducibility and regularity for certain applications such as cold cathode arrays or defect-free waveguides with low losses. Up to now different attempts have been made to form a highly ordered PS with a regular pore structure. In this work we present results of our study of the PS formation by electrochemical anodization at a pulse mode. The PS layers were formed in n+-type silicon wafers using an aqueous 9 % solution of HF as an electrolyte. A single cycle of the pulse mode consisted of two current density peaks of 100 mA/cm2 for 1 s in a forward direction and 5 mA/cm2 for 0.5 s in a reverse direction divided by 4 s intervals at a zero current density. PS pores grew perpendicularly to the silicon wafer surface. No branching, typical to PS formed at a constant mode, was observed. An average pore diameter was 80 nm. A dispersion of the pore diameters was less than 20 %. Thickness of silicon crystallites forming porous silicon skeleton was 20 nm. A distance between pore centers was constant across the whole PS. The highest aspect ratio of the pores achieved in the present study was 1:600. It was shown that PS formed by the developed technique is a promising template for the fabrication of nanocomposites with a high anisotropy. The work has been supported by the Belarus Government Research Program grants 1.1.14 and 2.4.16.

B.11.5
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09:30
Authors : Federico Ferrarese Lupi,1 Tommaso Jacopo Giammaria,1 Flavio Giovanni Volpe,1 Monica Ceresoli,1 Gabriele Seguini,1 Michele Perego,1 Luca Boarino,2 Diego Antonioli,3 Valentina Gianotti,3 Katia Sparnacci,3 Michele Laus 3
Affiliations : 1) Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20846 Agrate Brianza (MB), Italy; 2) Nano Facility Piemonte, Electromagnerism Division, Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, Torino, 10135, Italy; 3) Dipartimento di Scienze e Innovazione Tecnologica (DIST), Viale T. Michel 11, Università del Piemonte Orientale “A. Avogadro, INSTM, Alessandria 15121, Italy;

Resume : Self-assembling (SA) diblock copolymers (DBCs) generate nanostructured patterns that could be useful for advanced lithographic applications. The ordering dynamics in polystyrene-b-polymethylmethacrylate (PS-b-PMMA) DBCs thin films under conventional thermal treatments in oven/furnace is extremely slow, resulting in limited correlation length values even after prolonged annealing at relatively high temperatures. In this study, we describe the pattern coarsening dynamics of both asymmetric PS-b-PMMA DBCs with molecular weight of 67 kg/mol treated in the Rapid Thermal Processing (RTP) system, as a function of the annealing parameters (i.e. annealing temperature Ta and time ta) and the film thickness. The proposed methodology allows obtaining in few seconds high correlation length values in PS-b-PMMA films of variable thickness, taking advantage of the amount of solvent naturally trapped within the film during the spinning process. Irrespective of the Ta (chosen between 230 and 270 °C), the correlation length increases steeply at first with a growth exponent φ = 0.38 and then more gradually (φ = 0.09) as a function of ta, with a well-defined threshold, which depends on the annealing temperature, thus suggesting the occurrence of two distinct growth regimes. The obtained results are in good agreement with behavior previously reported by our group for symmetric PS-b-PMMA DBCs.

B.13.2
10:00
Authors : Jacopo Frascaroli(1)(2)(3), Stefano Brivio(1), Federico Ferrarese Lupi(1), Luca Boarino(2), Michele Perego(1), Sabina Spiga(1)
Affiliations : (1) Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20864 Agrate Brianza (Italy); (2) INRiM, Divisione Elettromagnetismo, Strade delle Cacce 91, 10135 Torino (Italy); (3) Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy);

Resume : Resistive random access memories (ReRAM) are one of the main candidates for future nonvolatile and high-density memory devices. We exploited the ability of PS-b-PMMA diblock copolymers to self-assemble in periodic nanodomains for the fabrication of patterned top metal electrodes of resistive switching devices. As opposed to serial lithographic techniques, block copolymer-assisted lithography is a cost-effective way for the parallel production of ordered surface features over the entire sample surface, keeping a tight control over their size and area density. We produced an array of patterned Ti/Pt bilayer electrodes on the surface of HfO2 films (3-6 nm thick) deposited on TiN by atomic layer deposition. Varying the copolymer molecular weight, we defined electrodes with a diameter of 20 and 28 nm and area density as high as 10¹¹ electrodes/cm². For the electrical characterization, each Pt/Ti/HfO2/TiN device was contacted by the sharp conducting tip of an atomic force microscope. By applying a potential difference between the top Pt/Ti and the common bottom TiN electrodes, we were able to modify the electrical conductivity of the selected device between a low and a high resistance value, probing the resistance memory mechanism at the nanoscale. Finally, the adopted fabrication method let us probe the device variability at the nanoscale, which was correlated with the density of inherent defects in the oxide film as a function of its thickness.

B.13.4
 
Self-Assembling for Nanofabrication II : Michele Laus
11:00
Authors : Guillaume Fleury(1), Karim Aissou(1), Muhammad Mumtaz(1), Wonsang Kwon(1), Yecheol Rho(1), Xavier Chevalier(2), Célia Nicolet(2), Christophe Navarro(2), Raluca Tiron(3), Eric Cloutet(1), Cyril Brochon(1), Georges Hadziioannou(1)
Affiliations : (1) LCPO-UMR 5629 Université Bordeaux-CNRS, 33405 Talence cedex, France; (2) ARKEMA FRANCE, Route Nationale 117, BP34- 64170 Lacq, France; (3) CEA, LETI, MINATEC Campus, 17 rue des Martyrs, 38054 Grenoble cedex 9, France

Resume : Perfectly ordered microstructures with nanometrically defined periodicity offer promising opportunities in microelectronics wherein the pitch reduction and the component density increase are two of the main challenges. To produce long-range ordered arrays inherent to such technologies, the combination of the “bottom-up” self-assembly with “top-down” guiding patterned templates has been successfully introduced leading to new technological breakthroughs wherein block copolymers are the cornerstone of the “bottom-up” nanofabrication processes through their self-assembly in periodic mesostructures. Well-ordered 2D-arrays of block copolymers can be produced by solvent or thermal annealing thin films cast onto grooved substrates. Consequently, directed self-assembly (DSA) of block copolymers stands out as a promising methodology to supplement conventional lithography. We have developed a first generation of lithographic materials based on the DSA of PMMA-b-PS and PMMA-s-PS copolymers synthesized by Arkema following the ITRS for the 22 nm node. Results summarizing this approach will be exposed during this talk. Nevertheless this system suffers from deficiencies such as a low Flory Huggins parameter and a low chemical contrast as regards to the etching processes which could be problematic for targeting sub-16 nm features. Consequently we have developed new systems which are characterized by high segregation strength as well as strong chemical etching contrast.

B.14.1
11:30
Authors : Federico Ferrarese Lupi,1 Tommaso Jacopo Giammaria,1 Gabriele Seguini,1 Michele Perego,1 Emanuele Enrico,2 N. De Leo,2 Matteo Fretto,2 Diego Antonioli,3 Valentina Gianotti,3 Katia Sparnacci,3 Michele Laus,3 Francesco Vita,4 Oriano Francescangeli 4
Affiliations : 1) Laboratorio MDM, IMM-CNR, Via C. Olivetti 2, 20846 Agrate Brianza (MB), Italy; 2) Nano Facility Piemonte, Electromagnerism Division, Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, Torino, 10135, Italy; 3) Dipartimento di Scienze e Innovazione Tecnologica (DIST), Viale T. Michel 11, Universit? del Piemonte Orientale ?A. Avogadro", INSTM, Alessandria 15121, Italy 4)Dipartimento di Scienze ed Ingegneria della Materia, dell?ambiente ed Urbanistica and CNISM, Universit? Politecnica delle Marche, Via Brecce Bianche, Ancona 60131, Italy;

Resume : Diblock Copolymers (DBCs) have attracted a wide interest over the last decades due to their ability to self-assemble (SA) into well-ordered nanometric size structures. In this work, we studied the SA process of cylinder-forming PS-b-PMMA block copolymers (BCPs) having different molecular weight (between 39 and 205 kg/mol), by means of a Rapid Thermal Processing (RTP) machine. With this annealing method, we were able to fabricate, in a relatively short amount of time, hexagonally packed cylindrical structures of different diameters ranging between 12 and 30 nm and center-to-center distance L0 from 24 to 73 nm. The study was performed on both flat pre-patterned surfaces. The SA process of BCPs inside densely packed and nanometer wide trenches was investigated as a function of the RTP annealing parameters (temperature and time). In particular, the ordering dynamic of the RTP treated BCP deposited inside the trenches showed an unexpected and irreversible flipping of the cylindrical nanodomains from parallel to perpendicular orientation with respect to the surface.

B.14.2

No abstract for this day

No abstract for this day


Symposium organizers
Gerard Ben AssayagNanoMat Group

CEMES-CNRS 29 Rue J. Marvig 31055 Toulouse Cedex 4 France

+33 5 62 25 79 24
+33 5 62 25 79 99
benassay@cemes.fr
Michele PEREGO (Main organizer)Laboratorio MDM, IMM-CNR

Via Olivetti 2 Agrate Brianza Italy

+39 039 603 6383
michele.perego@mdm.imm.cnr.it
Paolo PellegrinoUniversity of Barcelona

Carrer Martí i Franquès 1 08028 Barcelona Spain

+34 934039164
+34 934021148
pellegrino@ub.edu