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Phonon Scattering (phonon + scattering)
Selected AbstractsQuasi-localized low-frequency vibrational modes of disordered solids: Study by single-molecule spectroscopyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2004A. V. Naumov Editor's Choice of this issue of physica status solidi (b) is the article [1] by Andrei V. Naumov et al. This paper is Part II (Part I see [2]) of a study on elementary excitations in glasses, presented at the 11th International Conference on Phonon Scattering in Condensed Matter, St. Petersburg, 25,30 July 2004. For his outstanding talk, Naumov received the new physica status solidi Young Researcher Award which was bestowed for the first time at this conference. The cover picture is a sketch of a glass with a single impurity molecule and one hypothetical quasi-localized vibrational mode. The broadening and shift of the chromophore spectral line are caused by the interaction with this mode. Andrei V. Naumov is senior scientific researcher and deputy head of the Molecular Spectroscopy Department of the Institute of Spectroscopy, Troitsk. His main research interests are experimental and theoretical studies of low-temperature dynamics of amorphous solids (glasses, polymers etc.) via high resolution laser selective spectroscopy techniques. The second Editor's Choice is an article by E. A. Eliseev and M. D. Glinchuk [3]. Eugene A. Eliseev is scientific researcher at the Frantsevich Institute for Problems of Materials Science of the Ukrainian National Academy of Sciences, Kiev. His research areas are the theory of size and correlation effects in ferroelectric materials as well as modelling of disordered ferroelectrics properties. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Proceedings of the 11th International Conference on Phonon Scattering in Condensed Matter (Phonons2004)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004Alexander Kaplyanskii The 11th International Conference on Phonon Scattering (Phonons2004) was held in St. Petersburg, Russia, 25,30 July 2004. Both theoretical and experimental results on studies in phonon physics and related phenomena were presented and discussed. Main topical areas were: Phonons in nanostructures, coherent phonons, phononic crystals and superlattices, ultrafast acoustics, solitons and nonlinear phenomena, electron,phonon interaction, phonons in glasses and disordered materials, phonon transport and imaging, quantum fluids, lattice dynamics, and Raman and neutron scattering. [source] Microstructure-Lattice Thermal Conductivity Correlation in Nanostructured PbTe0.7S0.3 Thermoelectric MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Jiaqing He Abstract The reduction of thermal conductivity, and a comprehensive understanding of the microstructural constituents that cause this reduction, represent some of the important challenges for the further development of thermoelectric materials with improved figure of merit. Model PbTe-based thermoelectric materials that exhibit very low lattice thermal conductivity have been chosen for this microstructure,thermal conductivity correlation study. The nominal PbTe0.7S0.3 composition spinodally decomposes into two phases: PbTe and PbS. Orderly misfit dislocations, incomplete relaxed strain, and structure-modulated contrast rather than composition-modulated contrast are observed at the boundaries between the two phases. Furthermore, the samples also contain regularly shaped nanometer-scale precipitates. The theoretical calculations of the lattice thermal conductivity of the PbTe0.7S0.3 material, based on transmission electron microscopy observations, closely aligns with experimental measurements of the thermal conductivity of a very low value, ,0.8,W,m,1,K,1 at room temperature, approximately 35% and 30% of the value of the lattice thermal conductivity of either PbTe and PbS, respectively. It is shown that phase boundaries, interfacial dislocations, and nanometer-scale precipitates play an important role in enhancing phonon scattering and, therefore, in reducing the lattice thermal conductivity. [source] Disordered quasicrystals: diffuse scattering in decagonal Al,Ni,FeJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2004E. Weidner High-resolution synchrotron data of near-Bragg diffuse scattering from decagonal Al71.5Ni23.5Fe5 quasicrystals were recorded. A dominant phasonic origin is ruled out because of the absence of a significant G, dependence. An analysis solely in the frame of thermal diffuse scattering (TDS) theory (phonon scattering) showed a good match between experimental and calculated data in the quasiperiodic layers, but with an improbable ratio of elastic constants, c66/c11 = 4.0. In situ high-temperature measurements up to 1000,K revealed an increase of the intensity distribution perpendicular to the scattering vector G. Huang diffuse scattering (HDS) arising from quenched local defects has a general appearance that qualitatively reproduces the observed symmetry and anisotropy. An interpretation based on both TDS and HDS contributions is given. [source] Isotope and disorder effects in the Raman spectra of LiHxD1,x crystalsJOURNAL OF RAMAN SPECTROSCOPY, Issue 8 2001V. G. Plekhanov Most of the physical properties of a solid depend on its isotopic composition in some way or another. Scientific interest, technological promise and increased availability of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled crystals. A great number of stable isotopes and well-developed methods for their separation have made it possible to grow crystals of C, LiH, ZnO, ZnSe, CuCl, GaN, GaAs, CdS, Cu2O, Si, Ge and ,-Sn with a controllable isotopic composition. Among these compounds, LiH possesses the largest value of the isotope effect. The great number of theoretical and experimental data suggest that the isotopic composition of a crystal lattice exerts some influence on the vibrational properties of crystals. These effects are fairly large and can be readily measured by modern experimental techniques (ultrasound, Brillouin and Raman scattering and neutron scattering). In addition, crystals of different isotopic compositions possess different Debye temperatures. This difference between an LiH crystal and its deuterated analogue exceeds a 100 K. Very pronounced and general effects of isotopic substitution are observed in phonon spectra. The scattering lines in isotopically mixed crystals are not only shifted (the shift of LO lines exceeds 100 cm,1) but are also broadened. This broadening is related to the isotopic disorder of the crystal lattice. It is shown that the degree of a change in the scattering potential is different for different isotopic mixed crystals. In the case of germanium and diamond crystals, phonon scattering is weak, which allows one to apply successfully the coherent potential approximation (CPA) for describing the shift and broadening of scattering lines. In the case of lithium hydride, the change in the scattering potential is so strong that it results in phonon localization, which is directly observed in experiments. The common nature of the isotopic and disorder effects in a wide range of crystals is emphasized. Copyright © 2001 John Wiley & Sons, Ltd. [source] Effect of heat treatment on various physical properties in Zr80Ni20 metallic glassPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2006I. Kokanovi Abstract The effect of heat treatment on various physical properties in Zr80Ni20 metallic glass has been investigated by means of differential scanning calorimetry and electrical resistivity measurements. Experimental values for the crystallisation temperature and activation energy of the crystallisation processes were derived by studying these processes at different heating rates. The electrical resistivity of the annealed samples up to a temperature slightly above the first crystallization exotherm decreases with decreasing heating rates and increasing annealing temperatures. The temperature dependence of the electrical resistivity of the samples has been interpreted in terms of the weak localization of electrons and contribution by electron,phonon scattering. The contribution by electron,phonon scattering increases with increasing the fraction of crystalline phases in the glass matrix. The superconducting transition temperature, Tc, of the Zr80Ni20 metallic glass annealed at heating rates of 60 K/min and 10 K/min up to annealing temperatures below its second crystallisation exotherm decreases with decreasing heating rates and increasing annealing temperatures. The homogeneity of the annealed Zr80Ni20 metallic glass is discussed by using the superconducting transition width as a criterion. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Exciton Aharonov,Bohm effect and emission kinetics in nanoringsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2006M. Grochol Abstract The Aharonov,Bohm effect of excitons and their relaxation kinetics are investigated within the model of semiconductor nanorings of zero width. The kinetic equations where calculated deformation potential matrix elements for an acoustic phonon scattering are used as an input are solved for the steady state. Photoluminescence quenching is observed for stronger magnetic fields when electron and hole are spatially separated. The non-radiative decay plays a decisive role. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Temperature degradation of the gain transition in terahertz quantum cascade lasers , the role of acoustic phonon scatteringPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2009Rikard Nelander Abstract The temperature degradation in terahertz quantum cascade lasers is investigated with the focus on the role of acoustic phonon scattering. A self-energy describing the electron-acoustic phonon interaction is derived and used to study the importance in transport and optical properties. We observe a strong degradation of the gain peak with temperature. Despite the very small coupling to electrons, the exclusion of acoustic phonon scattering alters the current and peak gain in the order of 5%. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Examination of an unusual grain boundary in CaF2PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004M.E. Msall Abstract We have examined a grain boundary in CaF2 using Phonon Imaging and Electron Backscatter Diffractometry (EBSD). Unlike the <111> twin boundary typically found in CaF2, the crystal grains on either side of the boundary are not simply related to any principle symmetry directions, and are not related to one another by symmetry operations of the cubic group. In spite of the high degree of misalignment of the crystalline lattices, phonons can pass this grain boundary without excessive energy loss. Phonon images of samples taken from different sections of the grain boundary show that the structural properties of the grain boundary are constant over a large area. Computer simulations of phonon scattering at the interface based on acoustic mismatch models demonstrate that the caustic positions are sensitive to small changes in the relative orientation of the two pieces and to the projection of the grain boundary on the image plane. EBSD gives the needed high precision measurement of the relative orientation, resulting in a superior model of phonon transmission through this very asymmetric interface. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||