Plenary talks
Semiconductor Nanowires: Mechanical Properties, Surface Chemistry and Impurities
Korgel B.A.
Departament of Chemical Engineering, Texas Materials Institute, Austin, TX 78712, USA Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, Austin, TX 78712, USA
For the past several years, we have been developing the supercritical fluid-liquid-solid (SFLS) approach to the synthesis of semiconductor nanowires. By this method, large quantities of crystalline nanowires can be made, such as a gram of silicon or germanium nanowires in a single reaction. With these large amounts of nanowires available, applications like functional non-woven fabrics, paper, absorbents and membranes, can be explored. Examples of Ge and Si nanowire paper will be presented, along with their properties, including solvent absorption properties, conductivity and photoconductivity. These applications depend on the nanowire surface chemistry and methods have been developed to chemically passivate and functionalize the nanowire surfaces. For example, Ge nanowires can be coated with covalently bound monolayers of hydrocarbon by thermally-induced hydrogermylation or thiolation. Ge nanowires with these passivation layers can withstand relatively harsh oxidative environments. Examples of the chemical stability of organic monolayer coated Ge nanowires will be presented. These nanowires are also mechanically flexible. We have tested the mechanical properties of Ge nanowires by fabricating single nanowire cantilevers and studying their resonant frequencies as a function of diameter to determine their elastic mechanical properties. Using TEM with in situ heating capability, the thermal stability of individual nanowires has also been studied. By examining the gold tip at the end of a Ge nanowire, the Au/Ge phase behavior was studied, along with the solid state diffusion of gold into the solid Ge nanowire. Our latest results regarding the mechanical properties of Si and Ge nanowires, and in situ probing of the thermal stability of Ge nanowires, will also be presented.Graphene-graphane-diamane nanostructures - modelling of geometry, electronic and mechanic properties
Chernozatonskii L.A.
Emanuel Institute of Biochemical Physics of RAS, Moscow, 119991, Russia
New results of simulations of new composite structures based on graphene [1], graphane [2] and diamane [3] are described.- "quasi 1D" superlattices and electronic waveguids based on graphene and graphene ribbons lined by chemically bounded hydrogen atoms [4].
- X-, T- and Y- two dimensional superlattices and electronics waveguids lined by chemically bounded hydrogen atoms or spaces between ribbons.
- The nanostructures based on bilayered ribbons.
- Atomic structure, elastic and electronic properties of diamane C2H based on chemically bound graphene layers covered by hydrogen on both sides and bigraphane-diamane nanostructures.
- Electronic and mechanical properties of different graphene-nanotubes structures based on binding of graphene ribbons with carbon nanotubes.
[1] K.S. Novoselov, A.K. Geim, S.V. Morozov, et al. Science 306, 666, 2004.
[2] D.C. Elias, R.R. Nair, T.M.G. Mohiuddin, et al. Science 324, 236, 2009.
[3] L.A. Chernozatonskii, P.B. Sorokin, A.G. Kvashnin, D.G. Kvashnin. JETP Letters, 2009 (in press).
[4] L.A. Chernozatonskii, P.B. Sorokin, J. Brüning. Appl. Phys. Lett. 91, 183103, 2007.
Spintronics: Magnetism and spin-dependent transport on the nanometer scale
Bürgler D.E.
Institut für Festkörperforschung, IFF-9 "Elektronische Eigenschaften", Forschungszentrum Jülich GmbH, Jülich, D-52425, Germany
Since the discovery of interlayer exchange coupling and giant magnetoresistance (GMR) in the 1980's spin-dependent transport in magnetic multilayer and nanostructures has attracted a lot of interest. The research was motivated by applications - i.e. GMR read-heads in computer hard disks and the magnetic random access memory (MRAM) - as well as exciting new phenomena, which nowadays constitute the research field called spintronics. The field rapidly developed from investigating magnetic multilayers with layer thicknesses in the nanometer range to a true nanotechnology, which explores magnetism and spin-dependent transport on a nanometer scale. Typical devices are sub-micron sized in all three dimensions. The recognition of spintronics as a pioneering field for future nanoelectronics culminated in the award of the Nobel Prize in Physics 2007 for the discovery of the GMR effect. I will highlight the historical development of spintronics and review interlayer exchange coupling, giant and tunneling magnetoresistance (GMR, TMR), and current-induced magnetization dynamics as the major novel phenomena of spintronics. For each of them I will introduce a comprehensible physical picture and discuss realized and potential applications.Carbon Nanotube: The Inside Story
Ando Y.
Department of Materials Science and Engineering, Meijo University, Nagoya, 468-8502, Japan
Carbon nanotubes (CNTs) were serendipitously discovered as a byproduct of fullerenes by direct current (DC) arc discharge; and today this is the most-wanted material in the nanotechnology research. In this brief review, I begin with the history of the discovery of CNTs and focus on CNTs produced by arc discharge in hydrogen atmosphere, which is little explored outside my lab. DC arc discharge evaporation of pure graphite rod in pure hydrogen gas results in multi-walled carbon nanotubes (MWCNTs) of high crystallinity in the cathode deposit. As-grown MWCNTs have very narrow inner diameter. Raman spectra of these MWCNTs show high-intensity G-band, unusual high-frequency radial breathing mode at 570 cm–1, and a new characteristic peak near 1850 cm–1. Exciting carbon nanowires (CNWs), consisting of a linear carbon chain in the center of MWCNTs are also produced. Arc evaporation of graphite rod containing metal catalysts results in single-wall carbon nanotubes (SWCNTs) in the whole chamber like macroscopic webs. Two kinds of arc method have been developed to produce SWCNTs: Arc plasma jet (APJ) and Ferrum-Hydrogen (FH) arc methods. Finally, some new purification methods for as-produced SWCNTs are also reviewed.Harmonic Detection of Resonance Method
Rao A.M.
Department of Physics and Astronomy, Clemson University, Clemson, SC 29634, USA
Methods for studying mechanical resonances in micro- and nano-sized cantilevers are critical for the micro- (MEMS) and nano-electromechanical (NEMS) based systems. Several transduction mechanisms have been developed which measure either the static deflection of the cantilever or the dynamic response, e.g. shifts in natural resonance frequency or changes in quality factor. However, these methods are not scalable for detection using micro- to nano-scale cantilevers. We have developed a novel technique termed the harmonic detection of resonance (HDR) method which is entirely electrical in nature, and is very effective in measuring resonances in commercially available silicon microcantilevers and cantilevered multiwalled carbon nanotubes. In the HDR method, a single cantilevered multiwalled carbon nanotube is placed parallel to and within 1-10 μm from a counter electrode and is forced into resonance by applying an ac voltage with a dc offset on the counter electrode. Extensive experimental and theoretical results will be presented which elucidate the behavior of mechanical resonances in these systems and prove that HDR is scalable from the micro- to the nano-scale. The simplicity and efficient performance of HDR is largely due to its ability to overcome the problem of parasitic capacitance which has significantly limited the capability of previous techniques. Sensing the presence or absence of gases in the vicinity of resonating micro-cantilevers using HDR will also be discussed. Due to its versatility and simplicity, HDR is expected to be widely used in future MEMS and NEMS devices.Invited talks
Halogen induced surface nanostructuring
Eltsov K.N.
A.M. Prokhorov General Physics Institute of RAS, Moscow, 1119991, Russia
Interaction of halogens with metal or semiconductor substrates could be considered as a base for future atomic scale technologies on a surface because modern knowledge of reaction mechanisms permits us to realize several ways to change local surface structure with precise accuracy. In the presentation, few examples of applications of halogen action with metals (Cu, Ag, Au) and semiconductors (Si, GaAs) are described. Cu,Ag,Au/Cl2,I2. During action of molecular halogens on metal surface two steps of chemical reaction are usually indicated: first step is formation of simple overlayer of halogen, second one - corresponding halide growth. At both steps new interesting atomic structures are found to form. As a result of structural phase transitions in halogen monolayer (iodine or chlorine) on (111) and (100) planes, uniaxially compressed structures of different stripe periodicity are formed. Very strong influence of atomic structure of halogen monolayer formed at first step of chemical reaction on growth process of metal halides is indicated. The results of interface layer structure decoding are presented for systems CuI(111)/Cu(100) and CuI(111)/Cu(111). In case of copper chloride growth on copper the heating of the unbroken CuCl film formed at 160 K to room temperature gives rise to chloride agglomeration into 3D islands with specific size distribution for each substrate plane ((100) or (111)). This is an indication of so-called self-assembling phenomenon, which is very important for the process of quantum dots formation in the semiconductor epitaxy. More complicated self-organized structures have been observed at low (LHe) temperatures. GaAs(001)/I2. For binary semiconductors (A3B5) selective interaction of halogens with one of the elements (A or B) could give an opportunity to change the surface enrichment and surface reconstruction, respectively. We have determined conditions of selective removing gallium atoms on GaAs(001)-(4×2) by molecular iodine. As a result, we are able to create c(6×6) and As-rich (2×4) structures starting from Ga-rich (4×2) if to combine molecular iodine adsorption in range of coverage 0.1–1.0 ML and thermal treatment at moderate temperatures 250–300 C. We have also found that at low coverage iodine removes gallium atoms only at atomic step edges. Such feature could be used for surface smoothing. Si(001)/Cl2. Action of electron beam on low temperature condensed molecular chlorine film (90-100 K) creates local chemical reaction resulting in formation of SiCl4. Further heating at 150-200 K comes to removing silicon tetrachloride from electron eliminated zone. As a result narrow channels of any configuration could be created on surface. Such procedure could be described in term of Electron Nanolithography with Atomically Sharp Resists (ENASR) if to use STM probe as an electron source.X-ray absorption spectroscopy as a tool for 3D nanoscale atomic structure analysis
Soldatov A.V.
Center for Nanoscale Structure of Matter, Southern Federal University, Rostov-on-Don, 344090, Russia
The status of modern theoretical analysis of the experimental x-ray absorption spectra to extract structural parameters will be presented. Novel method for extracting of 3D structural information on the basis of advanced quantitative analysis of X-ray absorption near edge structure (XANES) realized in "FitIt" software will be described. The approach is based on the fitting of experimental XANES data using multidimensional interpolation of spectra as a function of structural parameters and advanced "ab initio" XANES simulations. Small number of required ab-initio calculations is the main advantage of the approach, which allows one to use computationally time-expensive non-muffin-tin methods. The possibility to extract information on bond angles and bond-lengths is demonstrated and it opens new perspectives of quantitative XANES analysis as a 3D local structure probe. As XANES spectrum can be measured simultaneously, one can use XANES to study the local structure in time-dependent experiments within a time domain of 100 picoseconds and less. Advanced theoretical analysis based either on self-consistent muffin-tin model or full potential (non-muffin-tin) theory, coupled with DFT geometry optimization have been applied to extract structural information from experimental XANES data. The status of modern research shows that XANES spectroscopy and its "ab initio" theoretical analysis can be a useful tool for the investigation of both local structure and electronic subsystem of many advanced materials without long range order. The present approach can provide a subatomic level (i.e., 0.01-0.03 Å) of accuracy in the determination of the interatomic distances and several of degrees in the determination of the bonding angles at specific atomic site of nanomaterials. In the framework of this approach, results of recent studies of local atomic structure for several types of nanostructures (nanoclusters, nanotubes etc.), polymers, catalysts, defects in semiconductors will be reported.Mechanical properties of individual nanostructures
Forró L.
Institute of Physics of Complex Matter Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015, Switzerland
We have elaborated a method for measuring the elastic moduli of individual nanostructures like carbon nanotubes, molybdenum disulfide nanotubes, inorganic nanowires, and their nanometer-sized bundles. It was found that the elastic coefficients strongly depend on the production method of these nanostructures and in some cases one can improve their Young's/shear moduli by various manipulations. This method has been applied for measuring the elastic response of cytoskeleton protein polymers, as well.Silicide nanostructured multilayers in monocrystalline silicon matrix: growth, structure and properties
Galkin N.G.
Institute of Automation and Control Processes of FEB RAS, Vladivostok, 690041, Russia
Semiconductor materials formed on the basis of embedded nanocrystallites, including semiconductor silicide (β-FeSi2 CrSi2 and Mg2Si) nanocrystallites in silicon matrix, can possess new optical, electrical and thermoelectrical properties, which are important for construction of new kinds of device structures in nanoelectronics and thermoelectronics. It is known, that iron disilicide nanocrystallites with large sizes (100-120 nm), which are far from quantum confinement regime, demonstrate electroluminescence in the energy range of 0.80-0.84 eV, when it's buried in the p-layer of silicon p-n mesa-diode. Increasing of β-FeSi2 number layers embedded in silicon lattice has shown the effectiveness of this approach from the point of view of luminescence increasing in grown structures. For the decrease of formation probability of misfit dislocation we propose to use an embedding of nanosize (5-30 nm) crystallites of β-FeSi2 and other silicides (CrSi2 and Mg2Si) in silicon lattice. In this work a growth and study of structure, morphology, optical, electrical and thermoelectrical properties of multilayer silicon - silicide heteronanostructures with buried semiconductor silicide (β-FeSi2, CrSi2 and Mg2Si) nanocrystallites (NC's) have been performed. Studies of nanosize (5-50 nm) island formation of Fe, Cr and Mg silicides on Si(111)7×7 and Si(100)2×1 surfaces, silicon growth atop nanosize silicide islands and multilayer repetition of developed growth procedure for all silicides have been carried out. Optimization of growth parameters has permitted to create monolithic multilayer heteronanostructures with buried nanocrystals (NC) of iron and chromium disilicides. It was firstly shown that β-FeSi2 nanocrystals (5-20 nm) are elastically embedded in silicon lattice due to introduction of tension in the NC lattice and silicon lattice around NC without formation of misfit dislocations on the interface. It gives the main contribution in photoluminescence signal at 0.79-0.81 eV. Optical properties and electrical properties of multilayer heteronanostructures have been studied and device perspectives have been discussed.The role of interfaces in determination of electronic properties of complex silicon nanoclusters
Avramov P.V.
Joint-Use Center, Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
The atomic and electronic structure of a set of novel complex silicon structures of different symmetry and composition were studied using semiempirical, ab initio DFT and post-Hartree-Fock methods. Based on the elaborated atomic models and theoretical calculations a set of novel nanoclusters were predicted and the key experimental data were interpreted. It was shown that electronic structure calculations at different levels of theory describe the quantum confinement effect in the experimental photoluminescence spectra of the nanocrystalline silicon with high accuracy. The band gap structure of newly proposed <110> oriented complex silicon nanowires display direct and indirect band gaps with different widths depending on size and symmetry of the objects. Systematically constructed new stable silicon nanocluster families with large arbitrary fullerene-type hollows inside and conglomerate structures on their base are designed by connecting the different number of tetragonal structural units. The clusters inherit a wide variety of structural and symmetry properties from their parent silicon fullerenes. Quantum dots and their conglomerates can host guest atoms in their hollows and therefore present a new promising type of nanomaterials with tunable electronic properties. Atomic structure of new exotic classes of silicon nanoclusters like nanoflowers and quantum dots embedded into nanowires as well as Y-shaped silicon and silicon carbide quantum wires were elaborated by connecting of several structural parts of the same or different symmetries. Using electronic structure calculations it was shown that QD/NW and NW/NW interfaces are energetically preferable and the band gaps of the embedded structures are closely related to the linear sizes of the longest constituting part, rather than the total linear dimension. The discovered atypical quantum confinement with a plateau and a maximum can be attributed to the substantial interactions of near Fermi level electronic states of the quantum dots and nanowire segments localized on different structural part of the nanoscale quantum clusters.Surface diffusion of Ge on Si(111)'5×5-5×5'-Cu surface
Saranin A.A., Gruznev D.V., Olyanich D.A., Chubenko D.N., Zotov A.V.
Institute of Automation and Control Processes of FEB RAS, Vladivostok, 690041, Russia Far Eastern National University, Vladivostok, 690650, Russia Vladivostok State University of Economics and Service, Vladivostok, 690600 Russia
Modification of the surface by the formation of the stable reconstructions changes the surface properties and opens the new possibilities for the controlled nanostructure formation. Incommensurate Si(111)'5.5×5.5'-Cu (denoted as "quasi-5×5" hereinafter) two-dimensional Cu2Si layer furnishes an example of such type of the reconstructions. We have found that in many cases "quasi-5×5" layer blocks the interaction between deposited adatoms and silicon substrate and for room-temperature deposition of Cu atoms results in the Cu nanowire formation [1]. It turns out that the diffusion of adatoms on the "quasi-5×5" occurs much faster than that on the clean Si(111)7×7 surface. In present work, we have studied surface diffusion of Ge adatoms on the "quasi-5×5" surface. The atomic arrangement of a "quasi-5×5" surface results in the formation of a quasi-hexagonal cells which are in fact form the so-called basins of attractions. At room temperature Ge atoms jumping within particular quasi-hexagonal cell. Since the STM scan speed is generally smaller than the speed of atomic motion, jumping Ge atoms appear in STM images as fuzzy regions. We rarely observed adatoms jumping from one cell to another. It should be noted that trapping atoms by quasi-5×5 unit cells is not limited to Ge. Similar behavior has been also observed for In and Au adatoms. Cooling the sample below room temperature results in the suppression of the atomic jumping and, as a result, all Ge atoms become frozen at their adsoption sites. As Ge coverage increases up to the saturation value of about 0.1 ML each unit cell becomes occupied by 2 to 5 Ge atoms forming dimers, trimers, etc. Further deposition results in the nucleation of the 3D Ge islands. We have determined the adsorption sites of the Ge atoms within "quasi-5×5" unit cell and the parameters of surface diffusion based on the first-principal total-energy calculations and STM observations.
[1] D.A. Tsukanov, M.V. Ryzhkova, D.V. Gruznev, et al. Nanotechnology 19, 245608, 2008.
Ferromagnetic/semiconductor Fe/Si nanostructures for spintronics
Ovchinnikov S.G., Bartolome J., Sese J., Varnakov S.N., Komogortsev S.V., Kosyrev N.N., Parshin A.S., Alexandrova G.A., Kuschenkov S.A., Dolbak A.E., Olshanetsky B.Z., Pchelyakov O.P.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660041, Russia Siberian Aerospace University, Krasnoyarsk, 660014, Russia Instituto de Ciencia de Materiales de Aragón, Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, Zaragoza, 50009, Spain Institute for Semiconductor Physics of SB RAS, Novosibirsk, 630090, Russia
In recent years the interest to multilayer magnetic structures (Fe/Si)n has increased in view of their unique physical properties and prospects for practical applications. The opportunity of achieving a semiconductor Fe-Si layer having spontaneous magnetization is also interesting for spintronics because it should result in an increase of spin polarization of electrons by transport through the magnetic heterostructure. In this talk we present some results obtained in a collaboration between several groups from Krasnoyarsk (Kirensky Institute of Physics and Aerospace Academy), Novosibirsk (Institute of Semiconductor Physics), and Zaragoza U University of Zaragoza, Spain). Thin films of Fe and nanostructures Fe/Si are produced by heat evaporation in the ultrahigh vacuum MBE machine "Angara" on the different substrates (Si100, Si111). Complex of the in situ studies includes the RHEED control of the sample quality, Auger- and EELS-spectra, and ellipsometry to obtain information on the interface thickness and sharpness, magnetic properties of the ultrathin layers by MOKE measurements. Ex situ studies include scanning AFM to study surface morphology, measureing sample magnetization in SQUID up to high temperature 800 K to study magnetic properties as function of temperature and magnetic field, and to separate magnetic properties of MeSi forming directly during the measuring at the interface. Recently we have prepared samples with adding the 57Fe isotope to specific layers to exploit layer-selective Mossbauer magnetometry. Due to the dependence of transport properties of the semiconductor spacer and the interlayer exchange coupling on carrier concentration we use a photoexcitation of Si electrons as the additional instrument to couple electronic and magnetic properties of magnetic nanostructure. We have shown the shift of magnetic resonance frequency induced by the photoeffect. This work is supported by RFFI grant 07-03-00320, project 4.1 of the OFN RAS, project 27.10 of the Presidium RAS, and the integration project 22 of SBRAS and DVO RAS.
[1] S.N. Varnakov, S.V. Komogortsev, S.G. Ovchinnikov, et al. J. Appl. Phys. 104, 094703, 2008.
[2] A.S. Parshin, G.A. Aleksandrova, A.E. Dolbak, et al. Tech. Phys. Lett. 34, 41, 2008.
Spin relaxation in type I QDs with indirect band gap structure
Shamirzaev T.S.
Institute of Semiconductor Physics of SB RAS, Novosibirsk, 630090, Russia
The spin of carriers and excitons in semiconductor quantum dots (QDs) has been paid much attention in recent research. The absence of any state with energy between the QD energy levels is expected to inhibit not only elastic but also inelastic processes of spin relaxation, such as phonon scattering [1]. This feature provides grounds for expectations that the relaxation mechanisms efficient in 3D may be suppressed in QDs, and as a result, an increase of electron and exciton spin relaxation time is expected. Recent experiments devoted to the study of the dynamics of the electron spin in InGaAs/GaAs QDs confirmed the long spin relaxation time of electrons which reaches ~20 ms [2]. In contrast, an experimental determination of exciton spin relaxation time in such QDs is inhibited by the short exciton lifetime of a few nanoseconds. Here we demonstrate that dynamics of exciton spin polarization can be studied in novel type I QDs system with electronic state belong to indirect value of the conduction band, which exhibits exciton lifetimes of up to several hundreds microseconds [3]. We present the experimental study of the exciton spin relaxation processes in such systems. This work was supported by the Russian Foundation for Basic Research under grant no.07-02-00134 and by the Program of Fundamental Studies of the Presidium of RAS (grant no.32).
[1] A.V. Khaetskii and Yu.V. Nazarov, Phys. Rev. B 64, 125316 (2001).
[2] M. Kroutvar, et al., Nature (London) 432, 81 (2004).
[3] T.S. Shamirzaev, et al., Appl.Phys. Lett. 92, 213101 (2008).
Single-wall carbon nanotubes for photonic applications
Obraztsova E.D.
A.M. Prokhorov General Physics Institute of RAS, Moscow, 119991, Russia
Since a first demonstration of a geometry-dependent photoluminescence of single-wall carbon nanotubes (SWNTs) [1] this material has found many applications in photonics. The most pronounced among them is the usage of SWNTs and SWNT-containing media as saturable absorbers in solid state lasers for realization of a mode locking regime and formation of sub-picosecond pulses. In this work our results on formation and optical studies of liquid [2] and polymer [3-6] media containing individual SWNTs are reported. The nanotubes synthesized by different techniques have been used to match the working spectral range of different solid state lasers. A dilution of the precursor suspension has been used for a controllable variation of the film and suspension losses. To increase the quantum efficiency of non-linear optical processes the nanotube fractions with a narrow diameter distribution have been created via ultrasonication with surfactants and a density gradient ultracentrifuging [7]. A complex optical diagnostics (Raman scattering, UV-VIS-NIR optical absorption, non-linear absorption (measured with Z-scan and pump-probe techniques) of SWNT-containing media has been performed.
Fig.1. The optical elements (mirrors, filters) based on single-wall carbon nanotubes.
[1] S.M. Bachillo, et al. Science 298, 2361, 2002.
[2] N.N. Il'ichev, et al. Quantum Electronics 34, 572, 2004.
[3] S.V. Garnov et al. Las. Phys. Lett. 4, 648, 2007.
[4] M.A. Solodyankin et al. Opt. Lett. 33, 1336, 2008.
[5] A.V. Tausenev, E.D. Obraztsova, A.S. Lobach et al. Appl. Phys. Lett. 92, 171113, 2008.
[6] A.I. Chernov, E.D. Obraztsova, A.S. Lobach. Physica Status Solidi (b) 244, 4231, 2007.
[7] A.I. Chernov, E.D. Obraztsova. Physica Status Solidi B, 2009 (accepted).
Digital etching of III-V semiconductors with a monolayer precision induced by electropositive and electronegative atoms
Tereshchenko O.E.
Institute of Semiconductor Physics of SB RAS, Novosibirsk, 630090, Russia
Novosibirsk State University, Novosibirsk, 630090, Russia
The development of atomic layer digital etching techniques is an important branch of nanotechnology. Digital
etching of III-V semiconductors with a monolayer precision can be realized by means of self-limiting surface reactions with adsorbates interacting selectively with atoms
of group III and group V. In this paper reversible transitions between the As-rich and Ga-rich reconstructions are experimentally observed under adsorption of cesium and
iodine on the GaAs(001) surface followed by heating in vacuum at moderate temperatures T=400-450°C. These transitions are explained by the element-specific
selectivity in the interaction of iodine and cesium with gallium and arsenic in the surface layer of GaAs(001). The observed cesium and iodine-induced transitions
between the As-rich and Ga-rich GaAs(001) surface reconstructions can be explained in a general way, by adatom-induced weakening of the bonds between the uppermost layer
of surface atoms with the substrate. This explanation was confirmed by the results of first-principles calculations of the cesium and iodine adsorbed on the As-rich and
Ga-rich GaAs(001) surfaces performed within the density functional theory. According to the calculated electron density redistribution between the adsorbates and the
substrate, deposition of cesium leads to the decrease of the binding energy of arsenic atoms with the substrate and, thus, facilitates the conversion from the As-rich
to the Ga-rich surface at reduced temperatures. On the contrary, on the Ga-rich surface iodine adatoms bind preferably with Ga atoms and weaken their bonds with the
substrate. This leads to the removal of uppermost Ga atoms and reverse conversion to the As-rich surface. The observed effect opens up opportunities for the atomic layer
etching of polar faces of III-V compounds.
Nanotechnology in space ultra vacuum conditions
Pchelyakov O.P.
Molecular Beam Epitaxy Department, Rzhanov Institute of Semiconductor Physics
SB RAS, Academician Lavrentiev prospect 13, Novosibirsk, 630090, Russia
Development of new scientific and engineering areas of nanoelectronics gives an impetus to high-tech precision nanotechnologies in ultra-vacuum, which can be generated near a spacecraft by means of a molecular shield. Among these technologies is the molecular-beam epitaxy (MBE) using solid and gaseous sources. The progress in the MBE technique have clearly demonstrated that this is the best method to fabricate epitaxial multilayer materials that have atomic-smooth interfaces, pre-set layer thickness, composition, and doping profile. The employment of highly sensitive electron-probe and optical control facilities allows for a high reproducibility of these parameters. These structures will be widely used in a new generation of nanoelectronics semiconductor devices and in the field of nanophotovoltaic applications. The basis of these devices, unlike conventional microelectronics, is the quantum wave nature of electrons. However, the terrestrial MBE technique imposes its limitations on the fabrication of high-quality structures. Synthesis of thin-film nanoheterostructures for creation of new generation devices demands maintenance in a technological zone of stable levels of vacuum of an order of 10-14-10-12 mm Hg., unattainable in land conditions. These limitations can be overcome through the use of a chamberless space technological facility arranged in the "wake" region of an orbiting shield. Therefore it is obviously necessary to use possibilities of space vacuum production engineering, as alternatives land, in the conditions of flight of orbit piloted complexes (Í = 250-400 km) [1-3]. We have analysed the data available in the literature and in the Internet on two projects (by USA and Russia). The first of these projects was launched by A.Ignatiev and C.W.Chu in the Space Vacuum Epitaxy Center (University of Houston) in 1989, and the second one by the Molecular Beam Epitaxy Department of the Rzhanovs Institute of Semiconductor Physics (ISP) in 1996. These Programs have as its final goal to create an orbiting manufactory in order to fabricate epitaxial semiconductor films with unique parameters applicable to opto- and nanoelectronics. From professor Ignatiev's evaluation, the space processing of the structures will cover the transport expenses and be profitable [1]. The prime objectives of our Project include the proof-of-principle, terrestrial refinement of mission scenarios and procedures semiconductor nanostructures, on large diameter silicon wafers. The first year's works were aimed at discovering physical factors which limit the attainable parameters of the heterosystems synthesized by the existing terrestrial ultrahigh vacuum MBE facilities. Specific Features of the draft design of a general-purpose automated MBE installation are discussed. Upon accomplishment of the project, a manufactory is to be designed on the orbit for processing of the alternative to expensive semiconductors perfect substrate material and multilayer nanoheterostructures synthesized on large size silicon wafers for the use in integral opto-, micro-, and nanoelectronics [2-3].
[1] A. Ignatiev.Earth Space Review, 2, 10, 1995.
[2] O.P. Pchelyakov, et al. Proc. of Joint X Europ. and VI Russian symp. on Phys. Sci. in Microgravity. 2, 144, 1997.
[3] O.P. Pchelyakov, et al. Semiconductor Vacuum Technologies in Space: Hystory, State and Prospects. Poverhnost'(Rus) 6, 69, 2004.
Novosibirsk State University, Novosibirsk, 630090, Russia
The development of atomic layer digital etching techniques is an important branch of nanotechnology. Digital etching of III-V semiconductors with a monolayer precision can be realized by means of self-limiting surface reactions with adsorbates interacting selectively with atoms of group III and group V. In this paper reversible transitions between the As-rich and Ga-rich reconstructions are experimentally observed under adsorption of cesium and iodine on the GaAs(001) surface followed by heating in vacuum at moderate temperatures T=400-450°C. These transitions are explained by the element-specific selectivity in the interaction of iodine and cesium with gallium and arsenic in the surface layer of GaAs(001). The observed cesium and iodine-induced transitions between the As-rich and Ga-rich GaAs(001) surface reconstructions can be explained in a general way, by adatom-induced weakening of the bonds between the uppermost layer of surface atoms with the substrate. This explanation was confirmed by the results of first-principles calculations of the cesium and iodine adsorbed on the As-rich and Ga-rich GaAs(001) surfaces performed within the density functional theory. According to the calculated electron density redistribution between the adsorbates and the substrate, deposition of cesium leads to the decrease of the binding energy of arsenic atoms with the substrate and, thus, facilitates the conversion from the As-rich to the Ga-rich surface at reduced temperatures. On the contrary, on the Ga-rich surface iodine adatoms bind preferably with Ga atoms and weaken their bonds with the substrate. This leads to the removal of uppermost Ga atoms and reverse conversion to the As-rich surface. The observed effect opens up opportunities for the atomic layer etching of polar faces of III-V compounds.Nanotechnology in space ultra vacuum conditions
Pchelyakov O.P.
Molecular Beam Epitaxy Department, Rzhanov Institute of Semiconductor Physics SB RAS, Academician Lavrentiev prospect 13, Novosibirsk, 630090, Russia
Development of new scientific and engineering areas of nanoelectronics gives an impetus to high-tech precision nanotechnologies in ultra-vacuum, which can be generated near a spacecraft by means of a molecular shield. Among these technologies is the molecular-beam epitaxy (MBE) using solid and gaseous sources. The progress in the MBE technique have clearly demonstrated that this is the best method to fabricate epitaxial multilayer materials that have atomic-smooth interfaces, pre-set layer thickness, composition, and doping profile. The employment of highly sensitive electron-probe and optical control facilities allows for a high reproducibility of these parameters. These structures will be widely used in a new generation of nanoelectronics semiconductor devices and in the field of nanophotovoltaic applications. The basis of these devices, unlike conventional microelectronics, is the quantum wave nature of electrons. However, the terrestrial MBE technique imposes its limitations on the fabrication of high-quality structures. Synthesis of thin-film nanoheterostructures for creation of new generation devices demands maintenance in a technological zone of stable levels of vacuum of an order of 10-14-10-12 mm Hg., unattainable in land conditions. These limitations can be overcome through the use of a chamberless space technological facility arranged in the "wake" region of an orbiting shield. Therefore it is obviously necessary to use possibilities of space vacuum production engineering, as alternatives land, in the conditions of flight of orbit piloted complexes (Í = 250-400 km) [1-3]. We have analysed the data available in the literature and in the Internet on two projects (by USA and Russia). The first of these projects was launched by A.Ignatiev and C.W.Chu in the Space Vacuum Epitaxy Center (University of Houston) in 1989, and the second one by the Molecular Beam Epitaxy Department of the Rzhanovs Institute of Semiconductor Physics (ISP) in 1996. These Programs have as its final goal to create an orbiting manufactory in order to fabricate epitaxial semiconductor films with unique parameters applicable to opto- and nanoelectronics. From professor Ignatiev's evaluation, the space processing of the structures will cover the transport expenses and be profitable [1]. The prime objectives of our Project include the proof-of-principle, terrestrial refinement of mission scenarios and procedures semiconductor nanostructures, on large diameter silicon wafers. The first year's works were aimed at discovering physical factors which limit the attainable parameters of the heterosystems synthesized by the existing terrestrial ultrahigh vacuum MBE facilities. Specific Features of the draft design of a general-purpose automated MBE installation are discussed. Upon accomplishment of the project, a manufactory is to be designed on the orbit for processing of the alternative to expensive semiconductors perfect substrate material and multilayer nanoheterostructures synthesized on large size silicon wafers for the use in integral opto-, micro-, and nanoelectronics [2-3].
[1] A. Ignatiev.Earth Space Review, 2, 10, 1995.
[2] O.P. Pchelyakov, et al. Proc. of Joint X Europ. and VI Russian symp. on Phys. Sci. in Microgravity. 2, 144, 1997.
[3] O.P. Pchelyakov, et al. Semiconductor Vacuum Technologies in Space: Hystory, State and Prospects. Poverhnost'(Rus) 6, 69, 2004.
Contributed talks (oral session)
Defining of relative stability criterion for different fullerenes formed in plasma
Fedorov A.S., Fedorov D.A., Avramov P.V.
L.V. Kirensky Institute of Physics of SB RAS, 660036, Krasnoyarsk, Russia
A new criterion which define a relative stability of different fullerenes formed in plasma is proposed. The criterion give the qualitative explanation of the row of different fullerenes yield (C60, C70, C36) during the plasma synthesis, while standard methods defining thermodynamic stability can not predict this row at all. The criterion is based on calculation of probability for molecule's chemical binds to stretch to some limit under thermal vibrations influence. At that the probability for molecule's chemical binds to stretch is calculated with help of central limit theorem under Lindeberg's condition and ab-initio calculation of vibration eigenvalues and eigenvectors.Computational Challenges for Mechanical Properties of Inorganic and Carbon Nanotubes
Enyashin A.N., Heine T., Seifert G., Ivanovskii A.L.
Institute of Solid State Chemistry of UB RAS, Ekaterinburg, 620990, Russia Physical Chemistry, Technical University Dresden, Dresden, D-01062, Germany School of Engineering and Science, Jacobs University, Bremen, D-28725, Germany
The elastic properties of the nanostructures attract a big attention since discovery of extremal mechanical characteristics of the carbon nanotubes and fullerenes (Yakobson et al. 2001, Ruoff et al. 2003). Though, the respective studies of mechanical properties of inorganic nanotubes are quite limited (Kaplan-Ashiri et al., 2008). In the present work we investigate using the density-functional based tight-binding method (DFTB) the behaviour of the carbon and inorganic (BN, MoS2 and imogolite) nanotubes under axial stretching and an anisotropic (nonhydrostatic) pressure causing by two metal gripes. Our calculations indicate quite different response in the case of the carbon and BN nanostructures against an anisotropic compression. Depending on an allotropic form at the intermediate nonelastic region can be obtained three possible variants of destruction: 1) "zipping" mechanism with the formation of zigzag-like edges, 2) the formation of diamond-like phase with sp3-hybridizied atoms and 3) the formation of an amorphous phase. Finally, the ordered (graphite stripes) or disordered (haeckelite-like stripes or islands) phases can be observed. Under lateral compression molybdenum disulfide nanotubes demonstrate the formation of nanostripes, which are always oriented in parallel to the surfaces of gripes, independently on the chirality of tubes. An imogolite nanotube does not break under these conditions, though, a release of water molecules is observed inside the nanotube. All carbon and inorganic nanotubes in the stretching simulations show almost harmonic behavior until rupture. However, all inorganic nanotubes in tensile tests demonstrate different behavior comparing with carbon nanotubes, where the formation of carbine-like chains is typical. BN and MoS2 nanotubes are brittle, whereas imogolite nanotubes should be ductile materials.The theoretical study of elastic properties of silicon nanowires
Sorokin P.B., Kvashnin D.G., Kvashnin A.G., Avramov P.V., Filicheva J.A., Chernozatonskii L.A.
Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia Emanuel Institute of Biochemical Physics of RAS, Moscow, 119991, Russia
Nanostructures, such as nanocrystals and nanowires (NW), represent the key building blocks for nanoscale science and technology. The nanowires are the most promising elements of the nanotechnology. They can be used as field-effect transistors (FETs), logic gates [1], and more. Another perspective technological field is to use the branched and hyperbranched nanowires. For example, the branched NWs might serve as building blocks to design 3D interconnected computing structure [2]. Presented here is a theoretical study of atomic structure and mechanical properties of the branched silicon nanowires of fork and bough types using model Tersoff interatomic potential. Using the extended cluster models, the effective Young elastic modules of the junctions were calculated. Our simulations were performed using classical molecular dynamics, in which the Si-Si interactions were described by model Tersoff potential [3]. The stiffness of the studied nanowires and nanotubes were compared with the literature. The nanowires junction behaves as springs up to contact of branches in contrast to similar Y-junctions of carbon nanotubes. The unloading of wires branches lead to they oscillation with fundamental frequency which is dependent from the wire's geometry. It was found that the stiffness of the wires is much larger due to crystalline structure of the wires. The effective Young modulus of nanowires with longer branch lengths were estimated.
[1] Y. Huang, X. Duan, Y. Cui, et al. Science 294, 1313, 2001.
[2] D. Wang, C.M. Lieber, Nature Mater. 2, 355, 2003.
[3] J. Tersoff, Phys. Rev. B 38, 9902, 1988.
Fabrication and frustrated magnetic states of ferromagnetic nanostructures
Fraerman A.
Institute for Physics of Microstructures of RAS, Nizhny Novgorod, 603950, Russia
We discuss the formation of frustrated states in magnetic nanoparticles caused by shape variations and by magnetostatic interaction in multilayer systems. The results of original investigations of magnetic states by magnetic-force microscopy (MFM) and the results of micromagnetic simulations are represented.Effects of magnetic field on the source current of deep-submicron MOSFET biased at accumulation
Baron F., Ovchinnikov S.G., Jiang H.-W., Wang K.L.
UCLA, Los Angeles, 90095, USA Siberian Federal University, Krasnoyarsk, 660036, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660041, Russia
We report the observation of the current peaks in the source current versus gate voltage characteristics of p-channel transistors when the devices are biased at the accumulation regime. The source current vanishes when the temperature exceeds 11 K. The source current can be enhanced dramatically as the transistors are exposed to a high magnetic field perpendicular to the channel. We believe the Fermi-edge singularity may be responsible for the resonant source current peaks. We also found that under a certain gate bias, the random telegraph noise (RTN) with an amplitude of 30 % is observed in the source current of the devices. The source-current RTN is strongly affected by applied magnetic field, which causes the large decrease of the average switching time of the source RTN. We believe that the random charging and discharging of single defects at the SiO2/Si interface of the gate-source overlap region may strongly disturb the band-to-band tunneling process, and thereby result in the source-current RTN.An Autonomous Dilution Microcryostat-Insert for Nano Physics
Edelman V.S.
P. Kapitza Institute for Physical Problems of RAS, Moscow, 119334, Russia
In an autonomous dilution microcryostat 3He circulates due to its condensation in the volume cooled by sorption pumping of 3He from a separate bath. A specific feature of this apparatus is the position of the sample holder in its upper part, which simplifies access to it [1]. The cryostat operates while inserted into a nitrogen-free portable (35 l) helium-filled vessel. The operating cycle of the cryostat includes the procedures of desorption, condensation, and cooling of the 3He-filled bath to 0.35-0.40 K and the mixer to 0.05-0.10 K (lasting ~1.5-2.0 h) and also a period of maintaining the temperature below 0.1 K (12-14 h). The amount of liquid helium in the portable cryostat is sufficient for operating for 6 days. The lowest reached temperature of the holder is 0.04 K. The instrument is mainly designed for cooling sensitive nano scale radiation detectors or for conducting of physical experiments with nano samples.
[1] V.S. Edelman. Instrum. Exp. Tech. 52, 301, 2009.
In Situ Measurement and Understanding the Size- and Loading Mode Dependence of Young's Modulus in ZnO Nanowires
Rigen Mo
Tsinghua University, Beijing, 100084, China
Elastic properties of one-dimensional nanostructures such as nanowires (NWs) are basic for their predictable and controllable applications to nano-devices and systems, and are being widely explored both theoretically and experimentally. In our research, a homemade in situ mechanical testing system is developed in SEM, based on which lateral bending and uniaxial tension of individual NWs can be realized with improved accuracy. Thereby, the diameter- and loading mode dependence of Young's modulus in single-crystalline ZnO NWs are studied. Bending moduli of ZnO NWs with diameters ranging in 17-550 nm are measured via electric-field-induced-resonance method, while tensile modulus of ZnO NWs with diameters ranging in 18-204 nm are obtained from stress-strain curves via uniaxial tension. Although recognized to be intrinsic in macroscopic objects, YM in the NWs reveals significant diameter dependence, which is also affected by the loading mode. Generally, the measured bending and tensile modulus for NWs with diameters smaller than about 120 nm increase dramatically as the diameters decrease, and are significantly higher than those of the thicker NWs which tend to the bulk modulus in ZnO[0001]. Further, tensile modulus increase more slowly then bending modulus with diameters decreasing from 120 nm to about 30 nm, while they get close for even thin NWs. Such diameter- and loading mode dependence of modulus are well explained with a core-shell composite NW model, which is developed based on energetic analyzing the radial-distributed bond length relaxation (i.e. the significant contraction near ZnO{1010} free surfaces, extending several atomic layers under surfaces and fading off slowly), correlated with the diameter-dependent elastic stiffening in both the shell and the core of NWs. Moreover, the model provides a universal approach to understand nanoscale elasticity related with different surface relaxation states and under various loading modes.The formation of nanosized metal-oxide ceramics on iron based
Chuprunov K.O., Levina V.V., Novakova A.A., Medentsov V.E., Falkova A.V.
Institute of Physical Chemistry of Materials, State Technological University "Moscow Institute of Steel and Alloys", Moscow, 119049, Russia Faculty of Physics, Moscow State University, Moscow, 119992, Russia
The purpose of development of nanosized metal-oxide ceramic composite materials (cermet) is to achieve a combination of physical, chemical, electrical and other properties, because initial components do not meet the requirements. Such materials can be applied in extreme conditions, such as temperature hits, aggressive media, in metallurgical production, in airspace industry, in catalytic processes. At present moment many methods can be used to fabricate cermets. However, due to surge of cermets application areas the problem of improvement and developing new methods of their fabrication is very relevant. Methods of synthesis of metal-oxide nanocomposites wich include chemical processes, such as co-precipitation, pyrolysis, reduction and others are very promising. Complex research of the formation regularities of Fe-Al2O3 and Fe2O3-Al2O3 compounds during their obtaining by chemical-metallurgical method was carried out by methods of Messbauer and X-ray, spectroscopy, electron microscopy and measurements of surface area by low temperature nitrogen adsorption. Waste of electrolytic production was used as iron-bearing precursor. The influence of chemical composition, the ratio of the components, the conditions of dehydration and reduction of oxygen-containing precursors on dispersion, phase composition, structure and morphology of nanosized materials has been found out. The influence of dimensional factor on the physico-chemical characteristics of the samples, and efficiency of their application for the creation of wear-resistant coatings has been shown. Present work has been carried out in the frame of project RFBR 07-08-0027.Modelling the Structure of Nanoparticle-embedding Matrices: Molecular dynamics in Li2B4O7
Marbeuf A., Kliava J.
Université Bordeaux I CNRS, Talence, 33405, France
As transparent magnets, borate glasses containing nanoparticles represent a new class of nanomaterials, promising for technical applications [1]. The parent crystalline phase Li2B4O7 (LTBc) has received much attention because of piezoelectric and nonlinear optical properties (second harmonic generation, SHG) related to its polar crystal structure [2]. A consistent approach in molecular dynamics (MD) is a powerful tool to predict crystal structure and to assure a continuity of physical properties between crystalline and glassy phases. In this work, a new model describing interatomic and angular interactions, taking into account periodic properties in borate-type solid phases, is presented and applied to LTBc through various simulations at temperatures ranging from 0 K to the melting point and through simulations in the pressure range 0 to 10000 MPa. The potential model differentiates between effective charges of three- and fourfold Boron atoms. MD-simulations were performed with DL_POLY [3], in isothermal and isobaric (NpT) or (NσT) isostress ensembles under periodic boundary conditions, on boxes of 13000 atoms. Simulation reproduces quite well cell lengths, atomic positions and distances in boron-oxygen polyhedrons and the polar nature of the symmetry group. The component of dielectric polarization along the c-axis (Pz) is found to decrease with increasing temperature above 200 K in agreement with SHG. The order-disorder type ferro - paraelectric transition of the second kind (Curie point TC≈839 K) is explained by a jumping of Li atoms between two lattice sites. By increasing or decreasing the pressure, the cell volume shows a discontinuity at pt ≈5000 MPa, implying the existence of a reversible first-order pressure-induced phase transition and follows below pt a Murnaghan law with B0=15.6 GPa as bulk modulus at ambient pressure and B0'=4.31 as first derivative. In the high pressure range, all Boron atoms are fourfold. The present approach can be directly applied to modelling the structure of nanosized systems.
[1] J. Kliava, I. Edelman, O. Ivanova, et al. J. Appl. Phys. 104, 103917, 2008.
[2] S-i. Furusawa, O. Chikagawa, S. Tange, et al. J. Phys. Soc. Jpn. 60, 2691, 1991.
[3] W. Smith, T.R. Forester, I.T. Todorov, DL_POLY Code, STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK.
Transparent glass-ceramics containing nanoparticles of transition and rare earth elements
Edelman I.S.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
In the first part of the paper the state of the art in the field of glass-ceramics containing nanoparticles of transition and rare earth elements is briefly outlined since their first observation to the latest results. Main attention is paid to transparent glass ceramics which have a wide spectrum of applications including active and passive components for magnetooptical devices, solar collectors, up-conversion devices, and laser active and passive media. In the second part the special case is highlight of borate glasses - a glassy system where doping with paramagnetic oxides results in formation of magnetic particles at very low contents of paramagnetic additions. The evolution of the phase state of paramagnetic additions is described in more detail at various stages of synthesis and subsequent thermal treatment of potassium-alumina-germanate-borate glasses co-doped with low concentrations of Fe2O3 and other metallic ion oxides, via, MnO, Gd2O3, Tb2O3, Dy2O3, Ho2O3, and Er2O3 monitored by a combination of different experimental techniques. The formation of magnetic nanoparticles confers to the glasses magnetic and magneto-optical properties typical of magnetically ordered substances. At the same time, they remain transparent in a part of the visible and near infrared spectral range and display a high Faraday rotation value. Besides, the presence of a large remnant Faraday rotation in these glasses allows keeping the light wave azimuth after switching off the magnetic field. These extraordinary physical properties of such "transparent magnets" - in combination with their chemical stability and compatibility with glassy elements of various optical devices, suppleness and comparatively low cost of the glass technology - make them good candidates for new optical and magneto-optical applications. The work is supported in part by RFBR-CNRS joint project, grant No. 07-02-92174.The study of Co/Cu multilayers by NMR method
Khalyapin D.L., Maltsev V.K., Kim P.D., Turpanov I.A., Betenkova A.Ya.
Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
In the present work we discuss the structure of magnetic layer in magnetron sputtered Co/Cu multilayers with different thickness of magnetic layer obtained by means of 59Co NMR method. The set of [dCoCo/dCuCu]100 samples was prepared with different effective layer thicknesses dCo≈2.5, 3.5, 4.5 and 10 Å and different Cu-layer thicknesses dCu. Structural analysis performed by XRD and TEM methods showed the fcc crystal lattice for all the samples. The sensitivity of NMR spectrometer was in the range of 150-250 MHz. In case of Co-layer thicknesses 2.5, 3.5 and 4.5 Å a spin-echo signal was detected only for small thicknesses of Cu-layer. The critical value of dCu when the NMR spectra were still measured was dCu=2 Å for dCo=2.5 and 3.5 Å and dCu=3 Å in the case of dCo=4.5 Å. It was found that the NMR spectra are mainly the superposition of two peaks with central frequencies f1=190-196 MHz and f2=208-213 MHz. These peaks are corresponded to Co-atoms which have 0 and 1 Cu-atom in the nearest-neighbor shell and the distribution of the central frequencies of resonance peaks is due to the influence of Cu-layers, which is different for different samples. For the [2.5Co/0.8Cu] sample a very wide distribution of resonance frequencies in the range from 150 to 212 MHz was detected indicating the structure of the sample is quite different from all the other examined samples and corresponds to the Co-Cu alloy. This alloy was metastable: the experiment with ageing indicates a drastic change in the shape of resonance spectra due to alloy decomposition although the one for other samples has been found to be almost stable. The observed peculiarities of NMR spectra as well as the results obtained with ageing are discussed in report.Nanoscience and Nanotechnology: from basic science to applications
Hedderich R.
Forschungszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany
The research activities at the Network NanoMat with his office at the Research Center Karlsruhe and at the University Karlsruhe in the area of nanoscience and nanotechnology are concentrated in the following fields: electron transport in nanostructures, nanomaterials, photonics and metamaterials, nanodevices and nanobiology. In these fields the researchers are closely cooperating within the Network NanoMat. A short overview of the activities will be presented. What successful cooperation among NanoMat partners can be like, is demonstrated by the nano antireflection coatings. 2 selected examples of research results from Karlsruhe will be presented: 1. The reversible change of physical, mechanical and chemical properties of metallic nanostructures has been shown for nanoporous structures and for thin films exposed to electrolytes. The tunability using an applied potential to control the change of properties is caused by the change of the electron density profile at the surface due to the electrochemical double layer formed in the electrolyte. 2. Energy storage is one of the key aspects of mobility and the use of regenerative energy sources. New nanostructured chemical compounds are developed as hydrogen storage materials in close cooperation of materials scientists, chemists and physicists.Contributed talks (poster session)
Theoretical study of interaction of transfer metals (Co, Fe) with Si (001) surface
Kuzubov A.A., Krasnov P.O., Kozhevnikova T.A.
Siberian Federal University, Krasnoyarsk, 660041, Russia Siberian State Technological University, Krasnoyarsk, 660049, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
Silicon and transfer metal compositions can be used widely in the spin and magneto electronic devices. Interaction of two transfer metals (Co, Fe) with Si (001) surface has been investigated at the presented work by the quantum-chemical methods. Calculations of sorption and diffusion of single metal atom in the different Si (001) sites has been performed as well as various possibilities of whole substitution of Si (001) surface at the diverse places.In situ magnetic spectroellipsometry
Zabluda V., Varnakov S.N., Efremov A.V., Kosyrev N.N., Rykhlitski S.V., Shvets V.A., Spesivtsev E.V., Khudjakov A.E., Shevtsov D.V.
Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, 660036, Krasnoyarsk, Russia
In situ measurements play a key role in the cost-effective manufacturing and -on the research side - in the better understanding of the process. As a fast, non-destructive, and precise optical method, spectroscopic ellipsometry (SE) has a broad range of applications, such as measurement of multilayer structures, surface roughness, composite materials like polycrystalline silicon, or damage depth profiles in ionimplanted materials. In situ applications of spectroscopic ellipsometry are becoming more and more important because of its high speed and accuracy. On the other hand magneto-optical Kerr effects (MOKE's) were first adopted to an in situ investigation of the magnetic properties of ultrathin Fe films. The MOKE's have been utilized as a premier surface magnetism technique. Due to the sub ML sensitivity, easy implementation, and local-probing nature, the MOKE technique was applied to various topics in thin-film magnetism including the magnetic phase transition, the magnetic anisotropy, the magnetic switching process, and the spin reorientation transition. Association of these two methods of research in the same installation opens new important experimental possibilities.Capillary Properties of Inorganic and Carbon Nanotubes towards Salts
Enyashin A.N., Seifert G., Ivanovskii A.L.
Institute of Solid State Chemistry of UB RAS, Ekaterinburg, 620990, Russia Physical Chemistry, Technical University Dresden, Dresden, D-01062, Germany
In spite of numerous experimental and theoretical studies of filling and crystallization of ionic compounds within carbon nanotubes (Sloan et al., 2002), studies concerning the behavior of inorganic, particularly, transition metal chalcogenide and BN nanotubes are limited. Though, recently, an experimental study of nanocapillary filling of inorganic sulfide nanotubes by a melt of PbI2 was performed (Kreizman et al., 2008), which opens new horizons in the fabrication of stable hollow halide nanostructures with unique electronic, luminescent and magnetic properties. We present the results of molecular dynamics simulations employing an effective Born-Mayer pair potential for the capillary imbibition of a drop of PbI2 melt into inorganic BN, MoS2 and carbon nanotubes. Radial atomic distribution functions were used to characterize the structure of the liquid inside of the nanotubes and the kinetics of the penetration. Our results show, that the main difference in the capillary filling process and the habitus of the embedded liquid among all three kinds of nanotubes will be caused by the structure of walls. Carbon and BN nanotubes, having weak interaction with the melt, need a longer penetration time than a nanotube of MoS2, having a stronger van der Waals' interaction due the sulfur. Though, the smooth surfaces of carbon and BN nanotubes provide a fast and friction-free drift into these nanotubes, while the sulfur surface of MoS2 does not accelerate the penetration of the molten PbI2 drop. All nanotubes show a complex dynamics of the filling, which is expressed in a shell-like structure of embedded liquid. The filling of MoS2 nanotube obeys a Lucas-Washburn equation, whereas the filling of carbon and BN nanotubes needs a modified description. Finally, the details of the imbibition process of liquid molecular halides (like TiCl4) into MoS2 nanotubes in comparison to those for molten PbI2 are also discussed. We find that the imbibition of molecular liquids with a weak van der Waals' type interaction between the molecules proceeds faster in comparison to the ionic melts, and it is completed also by the formation of a shell-like structure of the embedded liquid. The authors are grateful to the support from Russian Foundation for Basic Research (grants 07-03-00026, 07-03-96061) and European Commission (ERC grant INTIF 226639).Reversible lithium intercalation into nitrogen-doped carbon nanotubes
Bushueva E.G., Okotrub A.V., Galkin P.S., Kudashov A.G., Bulusheva L.G.
Nikolaev Institute of Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia
The anodes of lithium-ion accumulator are made usually from carbon materials. These materials have layered or porous structure, developed surface, high conductivity and chemical inertness. Therefore, they can show reversible lithium intercalation. One of such materials can be nitrogen-doped carbon nanotubes (CNx). Usually, nitrogen atoms incorporate into graphene sheets of CNx during synthesis. It leads to occurrence of defects of graphite network. [1]. It is clear that the electrochemical performance of a CNT-based anode can be significantly improved because of the diffusion channels for lithium ions into and out of the CNT core. It is possible to expect, that a specific capacitance of a CNx nanotube material will increase considerably, and the irreversible capacitance will decrease. Thus, CNx nanotubes can be a perspective material for anode of lithium-ion secondary cell. Charge-discharge characteristics of CNx nanotubes with the different nitrogen content were measured in our work. The preparation of cells and electrochemical measurements were carried out in special glove box in argon atmosphere. The plates of metallic lithium were used both as auxiliary and reference electrodes. The electrolyte was LiClO4 (1Ì) in propylenecarbonate (PC)/1,2-dimetoxyethane (DME) 1:1 mixture. Polypropylene fabric was used as a separator. The working surface of an electrode was about 1 cm2, the charge/discharge current was 1 mA. The working electrode potential was measured relatively to the lithium reference electrode. It has been established, that increasing of nitrogen content in carbon nanotubes from 0.5 up to 1.2 % leads to increasing of specific capacitance more then 2 times from 53 up to 125 mAh/g.Synthesis and properties of TiO2-SiO2 photocatalysts for water purification
Fedotova M.P., Voronova G.A., Emelyanova E.Y., Vodyankina O.V.
Tomsk State University, Tomsk, 634050, Russia Tomsk Polytehnic University, Tomsk, 634050, Russia
In our work UV- and visible active TiO2-SiO2 photocatalysts were successfully prepared by sol-gel method. The amount of TiO2 was varied from 60 to 90 % wt. All system were modified by the nitrogen-conteining substensis to increase photoactivity in destruction of methylene blue as a model compaund. Catalytic systems were characterized by X-ray diffraction, transition electron microscopy, IR-spectroscopy, ultraviolet-visible method (UV-method). Using XRD it was shown that of TiO2 phase prepared was anatas, and the average size of TiO2 is 9-10 nm. The photocatalytic activity of synthesized catalysts was compared with the one of commercial Degussa P25 catalyst under similar conditions. According to experimental results the photocatalytic activity of all our TiO2-SiO2 systems were higher.Magnetic Schottky barriers for electron spin detection
Tereshchenko O.E., Shamirzaev T.S., Gilinsky A.M., Toropov A.I , Dmitriev D.V., Lamine D., Paget D., Lassailly Y., Peretti J.
Institute of Semiconductor Physics of SB RAS, Novosibirsk, 630090, Russia Novosibirsk State University, Novosibirsk, 630090, Russia Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, Palaiseau, 91128, France
The electrical and magnetic properties of Schottky barrier diodes (SBD) based on Pd/Fe/GaAs(001)/InGaAs heterostructures have been investigated. One possible practical application of such structures consists in the realization of an electron spin-detector for free electrons based on the spin filter effect [1]. The Pd/Fe thin layers were deposited on the GaAs surface passivated by a thin oxide layer prepared by UVO3 techniques and clean, reconstructed (2×4) and (4×2) GaAs(001) surfaces prepared by chemical treatments in HCl-iPA solutions and annealed in UHV [2]. The surface composition, structure and electronic properties of the starting surfaces were studied by means of XPS, LEED, HREELS and photoreflectance. The electron transport and electronic properties of the Schottky structures were characterized by current-voltage (I-V) and electroreflectance measurements. The magnetism of the Fe layers was characterized by a magneto-optic Kerr (MOKE) experiment in air. The main results are promising for future electron polarimeters, both from the point of view of magnetism and electron transport. The magnetization of the Pd/Fe layers was found close to that of a bulk Fe layer of equivalent thickness and isotropic for Fe layers deposited on clean GaAs surfaces and anisotropic for magnetic layers grown on oxide covered surfaces. Such differences are attributed to the interface roughness and metal evaporation geometry. For the oxide interface, the Schottky behaviour is almost ideal, since the I(V) curve can be very well interpreted by the thermoionic equation, using an ideality factor b=0.7 eV, φn=1.02 and a surface barrier For the SBD's prepared by Fe deposition on the reconstructed GaAs(001) surfaces and passivated by nitrogen the ideality factors and barrier heights were found in the range 1.02-1.2 and 0.70-0.8 eV, respectively. The dependence of build-in surface electric field as a function of applied voltage was measured by electroreflectance and discussed in terms of Fermi level pinning by surface states at the interface metal/semiconductor. The spin light emitting diode (LED) was designed to provide injection of spin-polarized electrons from epitaxial Fe film contacts into GaAs/InGaAs quantum well (QW) LED structure. We observed a difference in the intensity of the EL spectrum when analyzed as sigma+ and sigma-, corresponding to 16 % of unpolarized light intensity and showed that the Pd/Fe/GaAs/InGaAs is a promising system for a spin polarimeter based on the optical registration of the spin filter effect.
[1] A. Filipe, H.-J. Drouhin, G. Lampel, et al. Phys. Rev. Lett. 80, 2425, 1998.
[2] O.E. Tereshchenko, S.I. Chikichev, A.S. Terekhov. J. Vac. Sci. Technol. A 17, 2655, 1999.
TDL spectroscopy of water vapor over an nanoporous adsorbent
Artemov V.G., Kapralov P.O., Tikhonov V.I., Volkov A.A.
A.M. Prokhorov General Physics Institute of RAS, Moscow, 119991, Russia
New kinetic effects occurring in water vapor which is exposed to a granular-nanoporous adsorbent filling an adsorption column have been recorded using a diode laser spectroscopy method (DLS). DLS operated in the mode of fast precise and wide band measurement in the water vapor pressure during contact of vapor with nanoporous adsorbent. Analysis of the time dependent input and output vapor pressures on the end of column revealed: 1) cascade character of water vapor diffusion into the column, 2) occurrence of water molecules with anomalously high mobility (precursors), 3) sign of separation of water vapor into the ortho- and para- spin-isomeric modifications.Tunneling Spectra at Terrace Boundaries on the Bismuth Surface with nano scale resolution
Edelman V.S.
P. Kapitza Institute for Physical Problems of RAS, Moscow, 119334, Russia
The scanning tunneling spectra of the trigonal bismuth surface are measured in the vicinity of the boundaries of terraces with a diatomic height [1]. It is found that the tunneling spectrum of the planar surface begins to transform at a distance of 2-3 nm from the terrace boundaries, specific features that are characteristic of the planar surface far from the terrace boundaries disappear, and new peaks in the density of states are observed. An analysis of the behavior of the current-voltage characteristics has revealed that one-dimensional electronic systems with a width of the order of an interatomic distance with their own individual spectra are formed at the ends of the rows of the atomic planes.
[1] V.S. Edelman. JETP 107, 251, 2008.
Application of inelastic electron scattering cross sections for quantitative analysis
Parshin A.S., Kushenkov S.A., Alexandrova G.A., Dolbak, A.E., Pchelyakov O.P., Olshanetsky B.Z., Ovchinnikov S.G.
Siberian State Aerospace University, Krasnoyarsk, 660014, Russia Institute of Semiconductor Physics of SB RAS, Novosibirsk, 660090, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
The values of the product of the inelastic mean free path and the differential cross section (λ·K) for inelastic scattering of electrons have been determined from the reflection electron-energy-loss spectra of nanostructures of the FexSi1-x and CuxSi1-x systems (0<x<1). Also the results of simulations of λ·K values for these composite nanostructures using specially developed software based on the dielectric theory are presented. A new approach to the quantitative analysis of components in such composite media is proposed.Ellipsometer mounting system design using CAD
Efremov A.V., Ovchinnikov S.G., Varnakov S.N., Kosyrev N.N.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660041, Russia
Ellipsometer arms mounting, that is a part of MBE system with magneto-optic ellipsometric complex, automated designing task is examined. The ability of limiting conditions driven design is shown. Mechanical analyses that prove dynamic stability are performed.Formation of nonmagnetic phases in Fe/Si interface
Varnakov S.N., Komogortsev S.V., Ovchinnikov S.G., Bartolome J., Sese J.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660041, Russia Siberian Aerospace University, Krasnoyarsk, 660014, Russia Instituto de Ciencia de Materiales de Aragón, Departamento de Física de la Materia Condensada, CSIC-Universidad de Zaragoza, Zaragoza, 50009, Spain
The magnetization of Fe/Si multilayers, grown by thermal evaporation in an ultrahigh vacuum system, was investigated at high temperatures. Magnetization and its temperature dependence up to a high temperature of 800 K depend on individual Fe layer thickness dFe. This dependence is the result of the formation of an Fe-Si interface layer (nonmagnetic phase) during the synthetic procedure. The fraction of this Fe-Si nonmagnetic phase is estimated versus dFe. At temperatures higher than 400 K an irreversible decrease in the magnetization occurs. A quantitative analysis of this irreversible behavior is proposed in terms of an exponential diffusion-like kinetic equation for the reaction that produces the Fe-Si nonmagnetic phase. The coefficients of the rate equation are the activation energy Ea and the prefactor D0, which have been determined for different dFe.Surface modified nano silica in polyurethane nanocomposites
Nigjeh M.M.A.
Imam Khomeini International University, Qazvin, 288, Iran
Some amine based coupling agents were used in surface modification of nano silica and modified particles have been applied in polyurethane nanocomposite formulations. In all composites mechanical and thermal properties evaluated in detail and showed the performance of modified nano silica in comparisons by unmodified, micro and unfilled composites. The chemical bond formation between nano particles and polyurethane matrices responsible for superior properties. Spectroscopy data used for modified nano silica characterization and SEM technique were done for cell size determinations in polyurethane nanocomposite foams, respectively. Also thermo mechanical properties of formulated nanocomposites have been evaluated by using thermal analysis methods.The theoretical investigation of mechanical properties of graphene
Kvashnin A.G., Sorokin P.B., Kvashnin D.G.
Siberian Federal University, Krasnoyarsk, 660041, Russia
The mechanical properties of the single graphene membranes were investigated by classical molecular mechanics (MM) simulation method. The graphene membranes of different diameters from 38 Å to 140 Å were studied and they Young's modulus was calculation. Also we investigated graphene membranes with vacancy defects with different concentration from 0.25 % to 7 %.Arc-discharge synthesis of multi wall carbon nanotubes
Kostas U.O., Terentyev D., Teplyh A., Nasonova L.I., Guselnikov A.V., Yudanov N.F., Okotrub A.V.
Nikolaev Institute of Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia Novosibirsk State Technical University, Novosibirsk, 630092, Russia>/br>
Strong C-C bonds forming cylindrical graphite shells, nanometer-scale size and high aspect ratio determine the unique mechanical properties of carbon nanotubes (CNT). High rigidity of the carbon cage is combined with durability and resilience of nanotubes, making their usage as reinforcing threads in high-viscosity nanocomposites highly appealing. The synthesis of multi wall nanotubes is performed in an electric arc discharge furnace. Graphite electrodes are evaporated by an electric arc in helium atmosphere, and then carbon atoms condense in the carbon nanotubes. Carbon nanotubes, produced by an electric arc method, were then oxidized in boiling mixture of concentrated sulfuric and nitric acids. Oxidizing continued for two hours. As a result, the nanotubes gained the ability to dissolve in water and form stable colloidal systems. The oxidation of the nanotubes' surface leads to appearance of hydrophilic groups. At the same time, amorphous carbon is also oxidized, which leads to its removal out of the system and consequently to the purification of nanotubes. The preparation of stable nanotube colloids allows for their injection in the polystyrene by co-polymerization. The resulting polymer-nanotube composite are expected to have new useful properties, such as higher durability and conductivity.Generalized lattice model of microheterogeneons states in multicomponent condensed systems
Potapova N.M.
Novgorod State University, Veliky Novgorod, 173003, Russia
On the basis of generalised lattice model transformed to the form of Ginzburg-Landau-Cahn-Hilliard. Equations for equilibrium distributions in the multi-component condensed systems are derived.The conditions for heterogeneous distributions of components are obtained. The connections between components characteristics, their interactions and parameters in binary solutions are established. Equilibrium distributions of the components in binary solutions with plane interfaces are derived. Connection between the concentration profiles parameters, interatomic potentials characteristics and temperature is established.Theoretical Study of Elastic properties of Branched Silicon Nanowires
Kvashnin D.G., Sorokin P.B., Kvashnin A.G., Avramov P.V.
Siberian Federal University, Krasnoyarsk, 660041, Russia
The atomic structure and elastic properties of Y-silicon nanowire junctions of fork- and bough-types were theoretically studied and effective Young modules were calculated using Tersoff interatomic potential. It was shown that boundary effects at junctions of different parts of the wires determine mechanical properties of the nanostructures. At the final stage of the bending new bonds between different parts of the junctions were formed. It was found that the stiffness of considered nanowires can be compared with the stiffness of multiterminal Y-type carbon nanotube junctions.Influence of catalyst composition on structure and properties of nitrogen-doped carbon nanotubes
Shlyakhova E.V., Okotrub A.V., Yudanov N.F., Bulusheva L.G.
Nikolaev Institute of Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia
The using of nitrogen-containing compounds in chemical vapor deposition (CVD) process results in nitrogen-doped carbon (CNx) nanotubes growth. CVD process variations (for example, temperature or catalyst composition) allow changing the total nitrogen content and CNx structure. Embedding of nitrogen atom can change electron properties of CNx nanotube. Catalysts used for CNx nanotubes growth were produced in result of thermolysis of doped transition metal tartrate calcium with common formula MexCa1-xC4H4O6·4H2O, where Me is transition metal (Co, Ni or their mixture). The goal of the investigation is study of catalyst composition influence on nanotube structure and composition and property of CNx material such as electron emission and electrochemical properties. CNx nanotube has been synthesized by acetonitrile vapor decomposition over catalyst particle produced in result of thermolysis of doped transition metal tartrate calcium at 850°C. Giving of acetonitrile vapors in CVD reactor are carried out in flow of hydrogen. X-ray photoelectron spectroscopy revealed the content in CNx nanotubes grows from 1.8 (Co) to 2.3 (Ni) at. %. TEM examination of the samples revealed the use of Ni as a catalyst component results in growth of carbon nanofibers, another ones result in CNx nanotube. The threshold value at 1 μA is equal to 1.6, 2.3 and 2.6 V/μm for CNx nanotubes grown over Co, NiCo and Ni nanoparticles, respectively. Measurements of current-voltage characteristics of the samples found the electron emission threshold is reduced with amount of nitrogen incorporated into CNx nanotubes.Investigation of autoemission properties of carbon nanotube arrays
Algaer J., Okotrub A.V., Guselnikov A.V.
Novosibirsk State University, Novosibirsk, 630090, Russia Nikolaev Institute for Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia
Production of flat light emitters of large area, high brightness and high transformation coefficient of electrical energy into light is one of the important problems of modern vacuum electronics technology. These displays can be used for lighting or as illumination in LCDs and TVs. Application of field emission effect of carbon nanotubes (CNT) cathodes is one of the possible trends in these technologies. Due to high aspect ratio, characteristic for CNTs, they have outstanding emission properties. Electric field in the vicinity of nanotube tip is hundred times bigger than the average in the volume, estimated as a ratio of voltage drop to interelectrode gap. As a result, emission current from CNTs appears at significantly lower values of applied voltage compared to traditionally used emission cathodes, made on basis of macroscopic metallic tips. Our work is to investigate the possibility of using CNT cathodes for production of flat panel lamps. Autoemission characteristics of flat cathodes were measured and uniformity and brightness of luminescence of emission centers were investigated. It was found experimentally that current-voltage diagram is dependant on interelectrode gap and applied voltage frequency. It is shown that in order to have good autoemission properties for CNT films their reciprocal screening has to be reduced. Design of a surface profiling rig is suggested. Dependence of relative luminescence on applied voltage is measured and it is shown that luminescence saturates quickly.New approach to determine equilibrium magnetization in magnetic nanostructures
Izotov A.V., Belyaev B.A.
Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
Determination of the equilibrium configuration of magnetic moments is the base of micromagnetic modeling, and plays a key role in studying magnetic microstructures, processes of magnetization reversal, in calculation of magnetic normal modes and absorption spectra in nanostructures. We offered new efficient approach for determination of the equilibrium magnetization in discrete model of a ferromagnetic. The solving of this problem is reduced to a system of the linear inhomogeneous equations with Lagrange multipliers. It enables to use comprehensive facilities of numerical algorithms of the linear algebra, to take advantages of sparse matrices and parallel computing.Dielectric properties of OLC/polystyrene composites
Sedelnikova O., Gavrilov N.N., Bulusheva L.G., Okotrub A.V.
Institute of Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia
Polymer composites find wide application in different areas due to their high-strength, lightweight, flexibility, thermal and chemical stability. Particularly, such materials absorb electromagnetic irradiation and can be used as shielding systems in wide frequency ranges. Application of carbon nanostructures in polymer composites will improve electromagnetic shielding efficiency. One of a new form of carbon is nanoparticles consisted of fullerene-like shells enclosed one inside the other, so-called onion-like carbon (OLC). Depending on the size and shape of agglomerates dispersed in the polymer matrix the composites can offer different properties. OLC obtained by thermal transformation of nanodiamonds have complex hierarchical structures. Primary particles are agglomerates of multi-shell polyhedron carbon cages often covered by an external graphitic mantle, the particles are readily agglomerated due to Van der Waals interactions and hydrogen bonding between functional groups presented on their surface. Destruction of OLC agglomerates is one of the important problems in the polymer composite processing. The dielectric properties of OLC/polystyrene polymer composites produced by forge-rolling were investigated. The structural organization of OLC particles in polystyrene matrix is determined from the modeling of permittivity measured for composites with different loading using the Maxwell-Garnett theory. It was found that forge-rolling method permits to milled OLC agglomerates in the smaller units and the particle size was evaluated. From comparison between the experimental and theoretical data it was proposed that for a high concentration of OLC in composite the units of aggregates are arranged in the chain-like structures. The percolation threshold is 20 mas.%.Electron-Electron Interactions in Moderately Doped Nanostructures
Dubois A.B.
Ryazan State Radioengineering University, Ryazan, 390010, Russia
The report is aimed at clarifying the contribution of intrasubband and intersubband electron - electron interactions to Landau quantization damping of transverse magnitoresistance oscillations. Expressions are derived for the time of electron-electron interaction, matrix elements of the full screening potential and dynamic dielectric function in a 2D electron system. The calculated dependences provide a good description of the experimental times of Landau levels collisional broadening. Presented for comparison are the calculated and experimentally measured curves for several nanostructure samples where 2D electrons are certainly known to fill only the lowest size-quantized subband.A New Method for Layered - silicate processing applicable in polymer - clay nanocomposites
Pourabbas B., Dadashzadeh M., Babalou A.
Department of Polymer engineering, Sahand university of Technology, Tabriz, 51335-1996, Iran
The clay treated by a new method (developed by authors), was employed in preparation of photo-polymerizable acrylate/clay nanocomposites with 5 % clay content and compared with those ones prepared using native sodium montmorillonite and an organically modified clay (cloisite 30B). The structure and properties of the nanocomposites were investigated by XRD, FTIR, TGA and transmission electron microscopy (TEM). The aim of the present work was to develop a new physical method to breakdown the clay layers and improve properties of clays to be applicable as nanometric fillers in polymer/clay nanocomposites. The method is based on the fast-freezing of the well-swelled natural Na-montmorillonite (Na-MMT). Specific surface area measurement performed by the standard Methylene blue adsorption method (ASTM-C324) provided proofs of 20-25 % increased surface area after treatment. The structure and morphology of the clays were investigated by X-ray diffraction (XRD), X-ray Fluorescence (XRF), Fourier transforms infrared spectrum (FTIR), scanning electron microscope (SEM) and thermo gravimetric analysis (TGA).Electronic trimmer structure with the intersite Coulomb interaction
Aplesnin S.S., Piskunova N.I.
Siberian Aerospace University, Krasnoyarsk, 660014, Russia Khakas Technical Institute, Siberian Federal University, Abakan, 655017, Russia
Triangular cluster containing three electrons is considered in terms of Hubbard's models with any parameters' of intra- (U) and intersite (V) Coulomb interactions and with three-center interactions in the external magnetic field. The account of intersite Coulomb interactions leads to quasi degeneration of levels on the chemical potential and to change of spin correlations in a certain range of values V/U. The gap near to chemical potential is disappeared in the certain magnetic field regions. The magnetic correlation and energy gap is simulated as a function of three-center interactions.The influence of currier gas flow rate on the growth of carbon nanotube arrays
Kurenya A.G., Gorodetskiy D.V., Kudashov A.G., Okotrub A.V.
Nikolaev Institute of Inorganic Chemistry of SB RAS, Novosibirsk, 630090, Russia
Mechanism of carbon nanotubes formation in chemical vapor deposition (CVD) process is determined by a number of parameters, such as, temperature, composition of reaction mixture, catalyst concentration, carrier gas flow rate, and time of synthesis. Altering these parameters leads to the change in the CVD process and, hence, the structure and properties of the carbon nanotube sample. In the present work we altered the rate of carrier gas flow and studied how this CVD parameter influences the thickness of carbon nanotube array. The catalyst particles were obtained in the result of thermolysis of ferrocene, which was also the supplementary carbon source. Toluene was used as main source for carbon nanotubes formation. The samples were synthesized at different argon flow rates 150, 200, 250, and 300 ml/min. The thickness of carbon nanotubes' array prepared with the rates of 200 and 300 ml/min is shown in fig.1. One can see that array thickness is dependent on the position of silicon wafer, used as a support for carbon nanotube growth, in CVD reactor. Zero position corresponds to the central point of the reactor. We suggested that the array thickness is determined by local temperature in different points of the reactor and checked the influence of the argon flow on the thermal profile. The curves obtained with argon flow rate 200 and 300 ml/min and without carrier gas are depicted in Fig. 1. One can see that increase the carrier flow rate leads to a change in the reactor thermal profile and, hence, in the hydrocarbon vapor concentration above the silicon substrates. For the flow rate of 200 ml/min the thickness of carbon nanotube arrays continually decreases when the substrate is approaching to the end of reactor, while for the flow rate of 300 ml/min the thickness increases. This result is connected with shifting of zone of hydrocarbon decomposition within the reactor with changing the carrier gas flow rate.
Fig. 1. Flow rate - caused thermal profile changes and array thickness change for 200 and 300 ml/min. Temperature - flow
dependence: 1 - no flow, 2 - 200 ml/min, 3 - 300 ml/min.Solid-state synthesis of the cobalt germanides in the epitaxial Ge/β-Co(001) è Ge/α-Co(110) nanofilms
Bykova L.E., Myagkov V.G., Turpanov I.A., Bondarenko G.N., Lee L.A., Kobyakov A.V.
Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
A studying of a chemical interaction of metals with various semiconductors demonstrates the interface possesses new structural and magnetic properties. A chemical interaction on a interface of films often activates solid-state reactions, which are a subject of intensive researches. Main efforts in this direction are concentrated on the studying of the silicides formation on a interface of metal films with silicon. The solid-state reactions of metals with germanium were studied to small degree. Most researches was shown, that with the increasing of the annealing temperature the Co5Ge7 phase has been formed by the first on the interface Co/Ge at temperature 300°C and then has been transformed in the CoGe2 phase at temperature 425°C. However, the chemical interaction and the epitaxial growth Ge on various surfaces β-Co and α-Co have uninvestigated. In this work the experimental study of solid-state synthesis of the cobalt germanides are presented in the epitaxial Ge/β-Co (001) and Ge/α-Co(110) nanofilms. The initial Ge/β-Co (001) and Ge/α-Co (110) films were prepared by the method of the thermal evaporation on the monocrystalline MgO(001) substrate in a vacuum 10–6 Òîðð. The obtained samples has been annealed in a vacuum 10–6 Òîðð through 25°C within 20 minutes from 100°C up to 350°C. Using x-ray diffraction, magnetic analysis, structural and chemical characterization of the interface between Co and Gr layers has been performed. At temperature 275°C all samples became fully nonmagnetic. It supposes full mixing of the layer Co with the layer Ge at this temperature and the synthesis of the nonferromagnetic cobalt germanides. We have established that for the both polymorphic modifications of cobalt, the phase Co5Ge7 has been formed by the first at temperature 275°C. With the annealing temperature increasing until temperature 300°C at the interface between Co and Gr layers, the phase CoGe2 has been formed and the electric resistance and the magnetic characteristics of the samples distinctly have been reduced. We have shown that various polymorphic modifications of cobalt do not change the formation sequence of phases and their temperatures of the initiation. On the basis of the carried out researches, we have assumed the existence of new structural transitions in area 275°C and 300°C in Co-Ge system.Synthesis and Magnetooptical Properties Of Nanogranular Co-Ti-O Films
Polyakov V.V., Polyakova K.P., Seredkin V.A., Zharkov S.M., Bondarenko G.V.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
Magnetic properties of granular films consisting of magnetic particles in dielectric matrix have been extensively described in last years. It is known that magnetooptical properties of composite system depend on properties of a dielectric matrix. The majority of researches are devoted metal particles in dielectric matrixes SiO2 and Al2O3. In this connection magnetooptical properties in TiO2 matrix with the dielectric constant exceeding corresponding value of SiO2 and Al2O3 are of interest. Most widespread of granular film prepared method is the co-deposition of metal and insulator. In this case the nanoparticles distributed in matrix randomly. On successive deposition of metal and insulator it can be realized self-organization in metal particale formation. In this report we present the magnetic and magnetooptical properties of Ño-Ti-O granular films received in conditions of solid-state reaction in layered film structure [1]. Solid state reaction CoO + Ti = 2Co + TiO2 was carried out in a mode of isothermal annealing at temperature 620-670 K in vacuum 10–6 Torr. Film structures with volume fractions of magnetic phase X = 0.2-0.52 have been received. Granular films of (50-100) nm thickness were prepared. The Co grain size was (10-100) nm. Investigations of magnetic properties of granular Co-Ti-O films have shown the following. The film magnetization curve of for X = (0.3-0.52) specify ferromagnetic character of interaction between magnetic granules. Magnetooptical spectra have been investigated in the wavelength range of visible light in a magnetic field up to 14 Oe. It is established, that spectral dependence of polar Kerr rotation of X = 0.28-0.52 are nonmonotonous unlike corresponding dependence of continuous Co films. It is shown also, that character of spectral dependence of Kerr rotation depends on magnetic fraction volume concentration of granular films. The curve of concentration dependence of polar Kerr rotation for wave length 630 nm contains tow maximum: of X = 0.28 and of X = 0.52. For X = 0.52 the enhancement of rotation in 2-2.5 times in the wave length range of 400-650 nm with a maximum on length of a wave of 600 nm is observed. It was established the correlation of concentration dependences of Faraday rotation and polar Kerr rotation on wave length of 630 nm. It is necessary to note that anomalies of magnetooptical spectra of the composite materials containing dielectric in the form of a layer or matrix, were observed [2] and have been predicted by theoretical calculation [3]. The mechanism of a magnetooptical rotation enhancement in granular films Co-Ti-O will be discussed. The work was supported by the Russian Foundation for Basic Research (RFBR projects no.08-02-00397-a, no.07-03-00190-a).
[1] V.G. Miagkov, K.P. Polyakova, G.N., V.V. Polyakov. JMMM 258-259, 358, 2003.
[2] Yu.A. Dynnik, I.S. Edelman, T.P. Morozova, A.Ya. Betenkova. JETP Lett. 65, 531, 1997.
[3] M. Abe, M. Gomi. Jpn. J. Appl. Phys. 23, 1580, 1984.
About the nature of induced anisotropy in amorphous Ñî-Ð films
Patrin G.S., Chzhan A.V., Kiparisov S.Ya., Seredkin V.A., Palchik M.G.
L.V. Kirensky Institute of Physics of SB RAS, Êrasnoyarsk, 660036, Russia Siberian Federal University, Krasnoyarsk, 660041, Russia
In this article results of experimental researches of the induced anisotropy in amorphous Ñî-Ð films received by chemical sedimentation are presented. Dependences of a field of the induced anisotropy on technological conditions of films reception and also heat treatments are established. Dependence of energy of the induced anisotropy on P concentration is defined. The qualitative model of the induced anisotropy in the investigated amorphous system is resulted. It allows to explain the received results. As is known, in amorphous magnetics there is no distant structural order and consequently in them occurrence of the magnetic anisotropy similar to those which is observed in crystal magnetics is impossible. However in such systems at imposing of an external magnetic field there can be uniaxial anisotropy. The physical reasons of its occurrence in amorphous magnetics are not found out, and existing models are based on analogy to polycrystalline systems. The decision of such problem represents actual interest both in fundamental, and in applied values. In this work results of experimental researches of the induced anisotropy in amorphous Ñî-Ð films are presented. Investigated samples were received by chemical sedimentation of elements on glass substrates in magnetic field intensity 3 êOe [1]. Then they were exposed to thermomagnetic processing under various conditions. In an initial condition (before heat treatment) investigated samples had uniaxial anisotropy and hysteresis loops in easy and hard directions looked like for uniaxial films. The coercivity was 0.15 Oe, an anisotropy field 15 Oe. Annealing in a magnetic field parallel to an axis of easy magnetisation did not lead to appreciable change of a hysteresis loop. Annealing in a magnetic field in a direction perpendicular initial an axis of easy magnetisation at a room temperature within several days leads to reduction of a field of anisotropy Ík with 15 to 8 Oe. Such heat treatment leads to growth of the coercivity (to 0.40 Oe). The samples received without external magnetic field that was reached by means of magnetic shielding (residual intensity of a laboratory field did not exceed 0.001 Oe [1]) we also investigated. In the samples received in such a way, there was no anisotropy and increasing coercivity was observed. Additional annealing of the films in a magnetic field induced uniaxial anisotropy again that narrowing of a hysteresis loop to the minimum values. In the work the experimental data establishing dependence of the energy of induced anisotropy in Ñî-Ð films from P concentration are also represented. For an explanation of the received results the model offered in [2] has been used. In our opinion it most comprehensible to an explanation of the induced anisotropy in investigated samples. According to this work, magnetic anisotropy is defined by position of magnetic atoms in relation to the next environment. Microscopic local axes of anisotropy for separate atoms have casual equiprobable distribution in all directions and consequently do not create macroscopical anisotropy. Such situation is realised in chemically besieged amorphous Co-P films received without of external magnetic fields. Imposing of a magnetic field in the course of reception of samples and annealing in a magnetic field create the allocated direction for distribution of local anisotropy axes and this results to occurrence of macroscopical anisotropy.
[1] G.V. Popov, S.Ya. Kiparisov, E.N. Matvejko, et al. Pre-print IFSD, 582F, Krasnoyarsk, 1989.
[2] J. Becker JEEE Trans. Magnet. MAG-14, 938, 1978.
Calculation of Holographic Scheme for Writing of a Planar Element with Nanodimensional Diffraction Structure
Batomunkuev Y.Ts., Karmanov I.N.
Optics and Optical Technologies Institute, Siberian State Geodesic Academy, Novosibirsk, 630108, Russia
It's known, that technologies of creation of nanodimensional volume structures are developing intensively in recent years. Successes in development of X-ray lasers [1] enable to manufacturing of focusing planar elements with nanodimensional diffraction structure by methods of volume holography. The object of the paper is the calculation of X-ray holographic scheme for recording of a planar focusing element working at 13 nm wavelength. Calculation of coordinates of sources for referent and object waves in this scheme is realized similar to the approach described in [2], considering thickness of the planar element.
Figure 1. Dependence of referent wave source coordinate dr (à) and object wave source coordinate do (b) on X-ray laser
wavelength
[1] E.N. Ragozin, I.I. Sobelman. Physics-Uspekhi 175, 1339, 2005.
[2] Yu.Ts. Batomunkuev. Materials of International Scientific Congress "GEO-Siberia-2006" - Novosibirsk, 76-78, 2006.
[3] V.V. Aristov, L.G. Shabelnikov. Physics-Uspekhi 178, 61, 2008.
Synthesis and Magnetic Property Features Of La-Sr-Mn-O Manganite Polycrystaline Films
Polyakova K.P., Patrin G.S., Patrusheva T.N., Velikanov D.A., Volkov N.V., Patrin K.G., Klabukov A.A.
L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia Siberian Federal University, Krasnoyarsk, 660041, Russia
It is known that properties of manganites with perovskite structure considerably depend on conditions of reception and the subsequent heat treatment. To an even greater degree it is possible to expect influence of a thin-film preparation conditions on physical properties of dilute manganites. In it work the results of research of magnetic properties of La-Sr-Mn-O polycrystalline films, received by an extraction-pyrolitic method, are presented. This method consists in component extraction from water solutions, mixing them in a specified ratio, deposition of the solution on a substrate and the subsequent pyrolysis. As a substrate the plates of a fused quartz were chosen. The solution with concentration of 2 % and 4 % has been used. After pyrolysis at temperature 770 K within 10 minutes the film was spent annealing on air at temperatures 870, 970, 1020 and 1270 K. Research of magnetic properties was carried out with use SQUID-magnetometer in a magnetic field up to 800 Oe and vibrational magnetometer in field up 20 kOe in the temperature range 4.2-350 K on the film samples received at two concentration of a solution (2 % and 4 %). The curve of magnetic reversal of film LaSrMnO, prepared from 4 % solution and subjected annealing at temperature 970 K represents itself a private loop of a hysteresis that testifies to absence of magnetic saturation. Character of temperature dependence is unusual for ferromagnetics. Similar dependence shows so-called "spin-glass" the properties observable at presence of ferromagnetic and antiferromagnetic phases. Such phenomena are marked at research of magnetic properties and of the dilute manganites. Even in fields up to 20 kOe a paramagnetic tale is observed, and saturation is not reached. In the case of film, prepared from 2 % solution, we have ferromagnetic behavior. Dependence of a kind of a curve of magnetization on annealing temperature is established in films received at concentration of a solution of 2 %. It was found that at low annealing temperature (~870 K) features of spin-glass-like behavior dominate in weak magnetic fields. At annealing temperature 970 K the spin-glass condition disappears in a magnetic field 600 Oe. The reasons of such behavior will be discussed. The work was supported by the Russian Foundation for Basic Research (RFBR project no. 08-02-00259-a, no. 0-802-00397-à).Activation of nanocrystalline polyethelene fibres by nonequilibrium low-temperature plasma
Sergeeva E.Al.
Kazan State Technological University, Kazan, 420049, Russia
Today one of the most actual ways of achievement of high durability of materials is creation of composite materials (CM) reinforced by nanocrystalline multifilament high performance high-modular polyethylene (HPHMPE) fibres. For activation of fibers it was applied nonequilibrium low-temperature plasma at the lowered pressure from 13 to 133 Pa. The orifice gases are argon, oxygen, air. The thermal component of cold plasma has been reduced to a minimum, due to low density of an ionic current arriving on a product, making 0.5-1 À/ì2 and small duration of influence of plasma on a fibre. Such plasma allows to process in it even higher-oriented HPHMPE fibers which are sensitive to heating, not causing their distraction. As matrixes it is used epoxy resins on a basis of bisphenol A diglycedile ether hardened by polyethylene polyamines and polyurethane. It is experimentally proved, that the application of plasma processing of fiber improves its wettability by epoxy matrix in the air on 86 %. The wettability of not-processed HPHMPE fibers sharply increased at replacement epoxy matrixes on polyurethane. In this case it is changed on 254 % or in 3,5 times. Plasma processing of the fibre at impregnation by polyurethane in the air additionally increase wettability on 34 %. Joint action of plasma and vacuum gives additionally raise of wettability on 173 % or about 2.7 times. Plasma are raised superficial energy of a fibre that allowed to operate the character on fibre-matrix interface interaction and strongly connect a fibre to a matrix. It gives possibility to receive monolithic high-strength CM polyethylene plastic, surpassing in specific durability metals in 6-7 times, fibreglasses in 2 times, and coal plastic in 1.5 times.Synchrotron Radiation as a Tool for an Operated Growth of Copper Nanoclusters
Soldatov A.V., Mazalova V.L., Mayanovic R.
Center for Nanoscale Structure of Matter, Southern Federal University, Rostov-on-Don, 344090, Russia Missouri State University, Springfield, MO 65804, USA
Synchrotron radiation is a powerful tool for an operated nanoclusters growth using radiolysis process and at the same time for their in situ investigation. Traditionally the pulse radiolysis is a technique for the elucidation of a variety of inorganic reaction mechanisms, especially in aqueous solutions. This technique is based on the formation of the radicals e–aq, H, and OH by the radiolysis of water. We have shown that irradiation of copper (II) chloride in aqueous solutions by synchrotron radiation in the absence of any stabilizer leads to the synthesis of metal nanoparticles. Moreover, X-rays used for the synthesis allow simultaneous in situ study of copper nanoparticles formation by X-ray absorption spectroscopy. The changes of atomic structure and chemical bonding were simultaneously monitored by means of x-ray absorption fine structure (XAFS) spectroscopy. XAFS analysis allows obtaining the detailed information on local and electronic structure with high sensitivity. Research objective of the copper nanoclusters obtained as a result of a radiolysis is study of a geometrical structure of clusters during of their growth using XAFS analysis and also an explanation of the energy shift of the XAFS spectra for clusters of different sizes. The theoretical analysis of x-ray absorption spectra were performed by the full-potential finite-difference approach and using optimized geometries calculated by the all-electron density functional theory. In the present work is shown that at initial stage the copper clusters grow in the structure which is different from the bulk copper. Part of the research (A.V.S. and V.L.M) has been supported by Russian Foundation for Basic Research, Grant No. RFBR 09-02-12257-ofi_m.Nanostructures of Dilute Magnetic Semiconductors: ZnO:Mn Films and Core/Shell Nanorods of ZnO/ZnO:Mn
Polozhentsev O.E., Kravtsova A.N., Mazalova V.L., Smolentsev G.Yu., Suchkova S.A., Sukharina G.B., Guda A.A., Smolentsev N.Yu., Ageev O.A. and Soldatov A.V.
Southern Federal University, Rostov-on-Don, 344090, Russia
Investigation of the local atomic and electronic structure of thin films ZnO:Mn and nanoscale core/shell structures (nanorods ZnO/film ZnO:Mn) have been performed. Such materials are dilute magnetic semiconductors (DMSs) and the creation of semiconductor nanorods with remarkable light-emitting properties and core/shell type structures with both magnetic and semiconductor properties are ones of the promising material candidates for spintronics technology. The structures are synthesized by carbothermal method and high pressure pulsed-laser deposition (PLD) method. Synthesis and growth of the studied structures have been considered in detail for the determination of Mn embeddings and impurities in ZnO host lattice. Their distributions crucially influence on magnetic and electronic properties and therefore the different positions (such as substitutional site, interstitial site, clustering and secondary phase) in the host lattice have been considered. The morphology of the samples have been characterized by scanning electron microscopy and energy filtered transmission electron microscopy. Local atomic and electronic nanoscale structure of the samples have been studied by the Zn and Mn K-edge x-ray absorption spectroscopy measured at the synchrotron radiation facility "SIBERIA-2" (Kurchatov Center of Synchrotron Radiation and Nanotechnology, Moscow) and at laboratory spectrometer Rigaku, Research Center for Nanoscale Structure of Matter, Southern Federal University, Rostov-on-Don, Russia. Theoretical analysis of x-ray absorption spectra has been applied to study peculiarities of local atomic and electronic structures using a self-consistent, real space full multiple scattering method (FEFF8.4 code) and a finite difference method (FDMNES2009 code). Band structure calculations have been performed with Wien2k-09 code. Local structure parameters have been refined using multidimensional interpolation approach on the basis of XANES fitting (Fitit2.0 code). Principal Component Analysis (PCA) (realized in Fitit 2.0 code) have been used to determine the concentrations of different secondary phase compounds in the spectra of studied compounds. The research is partially supported by grants of RFBR (Russia)-Academy of Science (Romania) 07-02-9187 and Ministry of Education and Science (Russia) 2.1.1.5932.Fluctuating of metals nanoparticles Young's modulus
Shushkov A., Vakhrouchev V.V., Shushkov A.V.
Izhevsk State Technical University, Izhevsk, 426067, Russia
Loading model of metals nanoparticles under the influence of hydrostatic pressure and point forces is submitted. Calculation results of Young's modulus of elasticity, deformation energy from nanoparticles dimension and loading are obtained.Excited Electronic States of Porphyrin-Fullerene Dyads with Different Type of Bonding
Krasnov P.O., Milyutina Y.M.
Siberian State Technological University, Krasnoyarsk, 660049, Russia Siberian Federal University, Krasnoyarsk, 660041, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036, Russia
The general requirements to the artificial photosensitive systems are the light sorption at the visible field of spectrum, the long excitation states lifetime and the possibility to form system with separated charges. For achievement of this aim it has been synthesized a lot of numbers of the different donor-acceptor porphyrin-fullerene dyads. Usually the electronic mechanisms of photoexcitation and charges separation are not described in these works, but their understanding will allow performing investigations more purposefully. In our work we present Time-dependent Density Functional Theory calculations of the porphyrin-fullerene dyads' electronic adsorption spectrum. It has been shown that their electronic adsorption spectrum takes a place in the visible part with the maximum wavelengths in the red part. The kind of bonding between porphyrin and fullerene does not influence on the nature of electronic transitions at excitations by the waves of red light. Electrons follow from the occupied porphyrin π-orbitals on the unoccupied fullerene π-orbitals at excitations in all cases, forming by this a system with separated charges. Lifetimes of excited states are about some hundred microseconds that is a few orders bigger than for natural reaction photochemical centers. Therefore dyads are able to store energy of excitation more efficiently. Increasing the distance between porphyrin and fullerene leads to displacement of red spectrum branch to the field of bigger wavelengths as also to decreasing of light adsorption intensity and increasing of lifetime at the excited states. It shows to the possibility to use efficiently the donor-acceptor dyads porphyrin-fullerene in the artificial photochemical centers for photosynthesis, in the photoelectron devices and, generally, in other light-sensitive materials.Investigation of probability distribution laws of structural properties of nanoparticles simulated by molecular dynamics method
Fedotov A.Yu., Vakhrushev A.V.
Izhevsk State Technical University, Izhevsk, 426067, Russia Institute of Applied Mechanics of UB RAS, Izhevsk, 426067, Russia
The calculation of macroscopic parameters of nanocomposites is a critical issue requiring the determination of power, structural-scale parameters, mechanical properties of nanoelements, as well as the investigation of formation and interaction processes of structural nanoelements constituting the composite. According to the investigations the main feature of nanoelements is as follows: when the characteristic size of nanoelements changes, their physical-mechanical characteristics (elasticity modulus, strength, deformation and other parameters) can change by an order conditioned by the reconstruction (not only monotonous) of nanoelement atomic structure and shape. Therefore the nanoelement characteristic size is one of the main parameters determining the nanocomposite properties. It should be pointed out that nanoelement formation processes, determining the structure and properties, carried out on atomic and molecular levels, are probabilistic or stochastic. Thus nanoelement parameters indicated always have a certain variation. So the probabilistic analysis of the distribution of nanoelement parameters is quite a critical task. This paper presents a mathematical model of condensation of composite nanoparticles in a gas phase. A series of computational experiments are carried out to simulate the formation of nanoparticles. Statistical data on the dimensional, structural and quantitative properties of metal nanoparticles are obtained. The estimating characteristics of sampled data are calculated. Statistical hypotheses concerning the probability distribution laws of the properties of nanoparticles are verified using the Pearson criterion. Histograms showing the distribution of the number of nanoparticles per unit volume, their average diameter and density, and the fraction of total mass of silver in nanoparticles are constructed.The study of vibration properties of silicon nanowires
Filicheva J.A., Sorokin P.B.
Siberian Federal University, Krasnoyarsk, 660041 Russia Emanuel Institute of Biochemical Physics of RAS, Moscow, 119334, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036 Russia
Nanostructures, such as nanocrystals and nanowires (NW), represent the key building blocks for nanoscale science and technology. Nanowires are the most promising elements of nanotechnology. A perspective technological field is to use branched and hyperbranched nanowires. Conceptually, such structures offer another approach for increasing structural complexity and enable greater functionality. The unloading of elastically-bent branched wires should lead to oscillations of branches with a frequency depending on branch lengths and diameters. Therefore such structures can be used as tuning forks with ultrahigh frequencies. In this work the vibration properties of branched silicon NW was calculated by classical molecular dynamics method. The frequencies and vibrational amplitudes of nanowires with different sizes are obtained. The dependence of nanowires fundamental frequency upon the branch lengths was estimated.The calculation of induction temperature coefficient of nanostructured hard-magnetic materials by molecular field method
Piskorskii V.P., Valeev R.A., Davidova E.A., Repina M.V.
All-Russian Scientific Research Institute of Aviation Materials, Moscow, 105005, Russia
The nanostructured hard-magnetic materials (Pr1-x-hDyxGdh)13-14(Fe1-yCoy)bal.B6-7 (x=0.18-0.58; h=0.05-0.33; y=0.2-0.36) with low induction temperature coefficient (α) (α=0 ÷ -0,02%/ºÑ) were studied. Value α was measured in the open magnetic circuit in temperature range 20-100°C (measurement accuracy ±0,005%/°C). α was calculated for the (Pr1-x-hDyxGdh)2(Fe1-yCoy)14B (ground magnetic phase) using molecular field model in the approaching of five magnetic sublattices. During the calculations sublattices Fe è Co was treated as whole F sublattice. Temperature dependence of sublattice ions magnetic moments was described by Brillouin functions BJ(x):
μF(T) = μF(0) BJf[μF(0)μBHF/kT]; μP(T) = μP(0) BJp[μP(0)μBHP/kT];
μD(T) = μD(0) BJd[μD(0)μBHD/kT]; μG(T) = μG(0) BJg[μG(0)μBHD/kT].
μF(T) and μP(T), μD(T), μG(T) - 3d metal ions
magnetic moments and Pr3+,Dy3+,Gd3+, respectively. Mi(0) - ions magnetic moments at Ò=0 Ê, and Hi(T) - molecular
fields (i=F,P,D,G). Molecular field coefficients nRF (R=D,P,G) was calculated using eq. (1). Curie temperature (TC) and coefficients α,
β, nFF were obtained from reference data [1].
TC α ( TC β - nFF) -n2RF = 0
— (1)
Mean deviation between calculated and experimental values of α is lower than 0.006%/°C.
Rather good correspondence between experimental and theoretical data displays that described model can be used for description of magnets Pr-Dy-Gd-Fe-Co-B.
The work was supported by RFBR grant ¹ 09-03-12103.
[1] E.N. Kablov, A.F. Kablov, A.F. Petrakov, et al. MiTOM 4, 3, 2007 (in Russian).
Atomic structure and electronic properties of beta-phase silicon nanowires
Demin V.A., Sorokin P.B., Avramov P.V., Chernozatonskii L.A.
Siberian Federal University, Krasnoyarsk, 660041 Russia Emanuel Institute of Biochemical Physics of RAS, Moscow, 119334, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036 Russia
The structure and properties of silicon nanowires under high pressure is almost a virgin field. Only in two papers [1,2] a study of silicon nanowires (SiNW) in different phases was reported. The existence of silicon nanowires in new phases opens the new promising field in nanomaterial science due to their unique properties. The electronic structure calculations of a set of silicon nanowires were carried out using density functional theory in the framework of local density approximation. We studied SiNW in different directions truncated from the bulk silicon in β-Sn phase and compared them with corresponding wires truncated from the bulk silicon in α-diamond phase. We calculated SiNW phase transition pressure. This value is lower than that observed in the bulk Si. This discrepancy can be explained by the misfit in strain energy of nanowires. SiNWs in α-diamond phase are more energetically favorable than SiNWs in β-Sn phase with nearly same effective diameter. The difference between wires in β-Sn phase of different orientations tends to zero with increasing of the wire size. All examined SiNWs in β-Sn phase reveal metallic properties.
[1] Y. Wang, J. Zhang, J. Wu, et al. Nano Letters 8, 2891, 2008.
[2] H.K. Poswal, N. Garg, S.M. Sharma, et al. JNN 5, 729, 2005.
The investigation of single nanotube of TiB2
Zaitsev A.A., Sorokin P.B.
Siberian Federal University, Krasnoyarsk, 660041 Russia Emanuel Institute of Biochemical Physics of RAS, Moscow, 119334, Russia L.V. Kirensky Institute of Physics of SB RAS, Krasnoyarsk, 660036 Russia
The crystalline form of titanium diboride (TiB2) has a P6/mmm space group symmetry, consisting of the stacking of alternate hexagonal boron and triangular titanium sheets. Among other interesting properties, TiB2 presents an attractive combination of mechanical, chemical and transport properties such as high hardness, low electrical resistivity, good thermal conductivity and chemical inertness [1], which turns this material an excellent candidate for several applications. The TiB2 nanotubes should inherit the attractive properties of the precursor crystal. Recently [2], it was shown, that the TiB2 nanotubes can be used for hydrogen storage with capacity up to 5.5 %wt. However a systematical study of the structure and properties wasn't carried out. In this work, the series of TiB2 nanotubes of different types and chiralities have been studied. Ab initio calculations of the binding energy, the electronic band structure, the density of states, and the dependence of the strain energy of the nanotube on the nanotube diameter for TiB2 nanotubes of different diameters are performed in the framework of the density functional theory.
[1] D. Ciuparu, R.F. Klie, Y. Zhu, L. Pfefferle. J. Phys. Chem. B 108, 3967, 2004.
[2] J.C. Barthelat, P. Durand, A. Sera?ni. Mol. Phys. 33, 159, 1977.