bluuebunny/crossref_metadata_2025_split huggingface dataset:
Consequences of Bloch's Theorem on the Dynamical Theory of Electron Diffraction Contrast
Authors: Metherell A. J. F. , Fisher R. M. 
Published: July 2007

AbstractSome consequences of Bloch's theorem on the diffraction of fast electrons in solids are considered. It is shown that the absorption coefficients of the various crystal wavefields excited in a crystal by the incident electron are periodic functions of crystal orientation. As a result it is shown that the two‐beam theory, when applied to the calculation of the absorption coefficients, results in a poor approximation. Recently several authors have shown that the higher‐order even reflections, such as the 222 reflection in Al or the 400 reflection in MgO, become vanishingly weak at certain critical values of the incident beam potential. From an investigation of the symmetry properties of the crystal wavefields a simple physical picture of this effect is obtained, and it is shown that at the critical voltage a reversal of the crystal wavefield symmetry occurs.
On the Theory of Surface States in Three‐Dimensional Crystals
Authors: Scherer M. , Phariseau P. 
Published: July 2007

AbstractThe existence of surface energy states of electrons in solids has been proved by Heine by matching the wave functions at the boundary plane. Starting from this general theory, we calculate the surface energy bands in three‐dimensional crystals with one atom per unit cell. Not only a semi‐infinite lattice but also a three‐dimensional crystal slab is considered. The method developed in this paper is a generalization of the Green's function method of Kohn and Rostoker for calculating the energy bands in infinitely extended crystals.
A Possible After‐Effect in Coarse‐Grained MnZn Ferrite of High Permeability
Authors: Buck O. , Roess E. 
Published: July 2007

AbstractMnZn ferrites of high initial permeability and different grain sizes have been studied. It was found that in materials with coarse grains the permeability and the harmonic distortion increase very rapidly with increasing induction whereas nominally the same materials with fine grains do not show this increase. A “pinning” interaction between ingrown pores and magnetic domain walls appears to be the cause of the rapid increase of permeability and distortion in the coarse grain ferrites. This interaction also causes the real part of the permeability and the maximum of the distortion to drop off at frequencies far below the eddy current cut‐off frequency and the gyromagnetic resonance frequency.
Beta‐Excitation of CdS Crystals
Authors: Schubert G. , Schnürer E. 
Published: July 2007

AbstractBeta‐excitation of CdS crystals with a majority blocking cathode and an ohmic anode gives rise to charge pulses in an integrating network. The analysis of the pulses allows to evaluate effective mobilities and lifetimes of the carriers and the electron—hole pair production energy. The values obtained are resonable and in agreement with those found by other authors, but the measured effective lifetimes are not identical with the high lifetimes of majority carriers typical for CdS in usual photoconductivity measurements. Care had to be taken to avoid space charge accumulation.
Short‐ and Long‐Range Order in Au3Cu
Authors: Airoldi G. , Asdente M. 
Published: July 2007

AbstractThe temperature dependence of the thermoelectric power of the Au3Cu alloy was measured for different states of order. While the disordered and the long‐range ordered states show qualitatively the same trend as the Cu3Au alloy, the short‐range ordered state shows different behaviour and a certain analogy with the long‐range ordered states. These results are discussed in connection with the new Bragg planes induced by the superlattice.
Latent Hardening in Rock‐Salt Type Crystals
Authors: Nakada Y. , Keh A. S. 
Published: July 2007

AbstractThe latent hardening in nine different crystals having the rock‐salt structure was studied as a function of prestrain. The latent hardening of a LiF crystal was also measured as a function of temperature. It was found that the latent hardening ratio of a crystal increases from 1.0 at zero strain to a maximum at about 0.5 to 1.5% compressive strain, then decreases to a constant value somewhat above 1.0. The maximum latent hardening ratio varies from 3.9 for LiF to 1.2 for AgCl. The difference in stress between the latent and the primary system in LiF remained essentially constant at all temperatures from 450 to 4 °K. The latent hardening ratio at 0.5% prestrain is 3.1 at 300 °K and 1.6 at 4 °K. Latent hardening was observed even above 300 °K where the flow stresses of the primary and the latent systems are essentially independent of strain rate and temperature. Dislocation distribution, revealed by etch pitting, was uniform during the primary slip, but was confined to widely separated bands during the latent hardening test. It is concluded that latent hardening in rock‐salt type crystals is caused primarily by the interaction of the glide dislocations in the latent slip system with the dipoles and dislocations in the primary slip system according to the dislocation reaction

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Trapping Levels in the Silicon—Silicon Nitride System
Authors: Kendall E. J. M. 
Published: July 2007

AbstractThe silicon—silicon nitride system has been examined using thermally stimulated current (TSC) techniques. The nitride was found to contain electron traps at between 0.50 and 0.90 eV below the bottom of the conduction band. A distribution of traps at or near the Si—Si3N4 interface and about 0.10 eV below the conduction band of the silicon was found. The TSC spectra clearly showed the dependence of the trap occupancy and trap structure upon applied electric field and temperature. Electron microscope and X‐ray work indicated that the nitride layers were not truly amorphous but contained very small crystalline areas.
On the Mechanism of Charge Carrier Generation in Thin Layers of Molecular Associates
Authors: Silinsh E. A. , Taure L. F. 
Published: July 2007

AbstractMeasurements are made of the dependence of the electrical current on voltage and sample thickness for thin layer systems of some molecular associates (MA) with intermolecular hydrogen bonds. The results show that the MA under investigation may be divided into two groups with respect to the mechanism of charge carrier generation in high electrical field (ϵ = 104 to 106 V/cm). For the first group of MA, the ohmic region of C—V characteristics is followed by a non‐linear injection region of space charge limited current (SCLC) type with a quasi‐continuous exponential trap distribution. At higher electrical fields (ϵ > 105 V/cm) the injection region passes to the dominating bulk ionization region. For the second group of MA the bulk ionization region follows directly after the ohmic region. The main experimental criteria of both mechanisms are discussed.
Ětude de la décomposition spinoïdale au microscope électronique dans les alliages CuNiFe
Authors: Cadoret R. , Delavignette P. 
Published: July 2007

AbstractL'étude du contraste a été effectuée en prenant comme modèle le mécanisme de décomposition spinoïdale prévu par Cahn [1 à 3] pour un alliage binaire cubique, dont l'énergie élastique est minimum suivant une direction β parallèle à <100>. Les contrastes effectivement observés au microscope électronique sur deux alliages Cux—(Ni0,7Fe0,3)y de composition initiale différente sont en accord avec l'analyse théorique de Cahn: déformation de la variation sinusoïdale de la composition avec le temps, manifestation plus rapide des phénomènes de croissance dans l'alliage de composition initiale le plus asymétrique.
Utilization of Symmetry in Solving the Boltzmann Equation
Authors: Mann E. 
Published: July 2007

AbstractBoltzmann's integral or integro‐differential equation may be reduced to a finite system of linear algebraic or simple integral equations if the kernel (the transition probability) is degenerate. This happens for elastic scattering of electrons by localized defects if the scattering is described in terms of Wannier functions. It is shown how the transition probability may be represented as a sum of terms transforming according to the irreducible representations of the point group of the problem. As a consequence, the system of linear equations is split into smaller systems. Since the calculation of the electrical current density involves only a few of these representations, only a few systems of smaller order need to be solved. The reduction procedure is described in detail for three examples with cubic, tetragonal, and orthorhombic symmetry.
Theory of Stark Effect in Crystals
Authors: Enderlein R. , Keiper R. , Tausendfreund W. 
Published: July 2007

AbstractThe change of the optical interband absorption of non‐conducting crystals in an external electric field is investigated. The degeneracy of the band structure is considered. The modification of the absorption by the electric field is shown to be the superposition of the Stark effect and of the Franz‐Keldysh effect. In particular, the transitions Γ → Γ and X5 → X5 in diamond type crystals are considered. The transition Γ → Γ shows a quadratic Stark effect and the transition X5 → X5 a linear one.
Relaxation von Fehlstellendipolen in AgCl‐Kristallen
Authors: Kunze I. , Müller P. 
Published: July 2007

AbstractEs wird über Messungen des thermischen Depolarisationsstromes (ITC) in mit V, Cr, Mn, Fe, Co, Ni, Cd und Pb dotierten AgCl‐Einkristallen berichtet. Die durch Assoziation aus Fremdkationen und Leerstellen gebildeten und durch Abkühlung im statischen Feld teilweise ausgerichteten Dipole verursachen bei Erwärmung mit 2° K/min durch ihre Reorientierung einen Depolarisationsstrom mit einem Maximum bei etwa 110° K. Aus diesen elektrischen „Glowkurven”︁ lassen sich die Sprungenthalpien, die Frequenzfaktoren und, bei bekannter Zahl der Dipole, auch die Dipolmomente bestimmen. Bei AgCl:Ni, AgCl:Cd und AgCl:Pb treten einfache ITC‐Kurven mit nur einem Maximum auf, während die in allen übrigen Fällen erhaltenen komplizierteren Meßkurven als Summe zweier einfacher ITC‐Kurven aufgefaßt werden können. Verursacht werden diese Doppelkurven durch die zwei Relaxationsmöglichkeiten, die bestehen, wenn die Leerstellen außer den nächsten Nachbarplätzen auch die übernächsten Nachbarplätze der Fremdionen besetzen.
Theory of Anharmonic Crystals. II. Linear Chain
Authors: Plakida N. M. , Siklós T. 
Published: July 2007

AbstractThe properties of the monatomic linear chain with nearest neighbour interaction are considered at fixed length and at constant external tension applying the dynamical theory of the anharmonic lattice developed in our previous work. The vibrational frequency, the damping, the internal energy, the specific heat, the average length and tension are calculated. It is shown that in the case of constant external tension the chain becomes unstable at sufficiently high temperature or at sufficiently high zero‐point energy. The critical parameters are obtained and the behaviour of the thermodynamical quantities in the vicinity of the critical point are investigated.
Polarity Inversions of the Photo‐Hall E.M.F.
Authors: Sakalas A. , Viščakas J. 
Published: July 2007

AbstractThe inversion of the sign of the photo‐Hall voltage is investigated in almost intrinsic semiconductors being illuminated with light in the region of the fundamental absorption. It is shown theoretically that single or double inversions are possible if only one type of centres is considered. The inclusion of traps gives single, double or triple inversions. Numerical solutions of these cases are represented. The experimental data agree well with the theoretical curves.
Recovery of Dilute Al–Si Alloys Cold‐Worked at −195°C
Authors: Hegazi A. , Kovács I. , Nagy E. 
Published: July 2007

AbstractIsochronal annealing data are presented covering the whole range of temperature (−195 to 600°C) for cold‐worked dilute Al–Si alloys. The role of the Si atoms in the creation of defects during the deformation and the recovery process is discussed.
Differential Reflection Spectra of Heavily Doped Silicon and Germanium in the Ultraviolet Spectral Region
Authors: Volfson A. A. , Subashiev V. K. 
Published: July 2007

AbstractThe effect of heavy doping on the reflection spectra of silicon and germanium is investigated by measuring the fractional change in reflectance, ΔR/R, between pure and doped materials. This effect arises from the narrowing of the forbidden gap in heavily doped materials. The form of the ΔR/R spectrum allows to reveal the critical points of the band structure, as in electro‐, piezo‐, or thermoreflectance measurements.
Photoluminescence of CdIn2S4 and Mixed Crystals with In2S3 as Related to Their Structural Properties
Authors: Czaja W. , Krausbauer L. 
Published: July 2007

AbstractIn this paper experiments on photoluminescence (emission and excitation spectra) of CdIn2S4 crystals and of mixed crystals with In2S3 at 77°K are reported. The results are interpreted on the basis of the partial inversion of the thiospinel CdIn2S4. In CdIn2S4 the two emission bands observed in the red spectral region are ascribed to a Cd ion at an octahedral site and an In ion at a tetrahedral site. This model describes the intensity and wavelength variation of the photoluminescence of the mixed crystal system CdIn2S4/In2S3 surprisingly well. Evidence is given that the energy gap in all these crystals is indirect. In an appendix some etching procedures are listed.
Orientation Contrast from Inclusions (Experiment)
Authors: Guyot P. 
Published: July 2007

AbstractThe diffraction contrast in transmission electron microscopy is studied for alumina particles dispersed in an aluminium matrix. The position of the inclusions in the foil is measured by stereomicroscopy. There is a good agreement with the intensity profiles previously calculated on the basis of the two‐beam dynamical theory for non‐diffracting inclusions in a diffracting matrix.
Investigation on the Magnetization Structure of Polycrystalline Uniaxial Ferrites with the Torsion Pendulum Method. I. Calculation of the Magnetic Stiffness
Authors: Voigt C. , Hempel K. A. 
Published: July 2007

AbstractUsing the formulas for the magnetic stiffness (torque per radian) of a ferromagnetic single crystal the stiffness of a polycrystalline sample performing small rotational oscillations in a homogeneous magnetic field with the axis of rotation perpendicular to the field direction is calculated. The sample is assumed to consist of non‐interacting crystallites with positive uniaxial magnetic anisotropy. The crystallites may be either in the single domain state or may be splitted up into domains according to the phase theory. The orientation distribution of the crystallites is supposed to have rotational symmetry with respect to a preferred direction.
Thermal Expansion of Silicon and Zinc Oxide (II)
Authors: Ibach H. 
Published: July 2007

AbstractCoefficients of thermal expansion α‖c and α ⊥ c between 4 and 800°K have been measured for zinc oxide using an interferometric and a capacitance method. Thermal properties of wurtzite lattices (two coefficients of thermal expansion and a pyroelectric constant) can be described in terms of three thermal equations of state. Two mechanical and one electrical Grüneisen parameters are defined and their temperature dependence is calculated from experimental results. The high‐ and low‐temperature limits of the Grüneisen parameters are compared with results obtained in other experiments. The values predicted from a rigid ion model are discussed.
Shock‐Induced Substructural Changes in Prestrained Iron
Authors: Mahajan S. 
Published: July 2007

AbstractDeformation structures of iron samples prestrained to various amounts prior to their exposure to 50 and 100 kbar shock waves have been examined by transmission electron microscopy. On shocking, the regions which had deformed during prestraining exhibit dislocation configurations characteristic of large‐strain room temperature deformation, and the undeformed areas develop substructures representative of very low‐temperature conventional deformation. Interactions between shock‐induced dislocations have also been analysed. Passage of a 100 kbar shock wave through samples prestrained 20% causes localized recrystallization. Experimental evidence favours the formation of nuclei for recrystallization by the coalescence mechanism.
The Energy Distribution of Field‐Emitted Electrons from GaAs
Authors: Hughes O. H. , White P. M. 
Published: July 2007

AbstractMeasurements of the energy distribution of field‐emitted electrons from clean GaAs surfaces indicate that the emission originates from the valence band. The distributions are found to be considerably wider than is predicted by theory despite the high resolution of the apparatus. The Fermi level at the surface of low‐resistivity n‐type material is found to be stabilized 0.54 eV below the conduction band edge indicating a high density of surface states. The surface state density is estimated to be greater than 2.8 × 1013 cm−2. Emission from within the forbidden gap is also reported.
Mechanical Behaviour of Crystals with Twinned Structure
Authors: Aoyagi T. , Sumino K. 
Published: July 2007

AbstractThe internal friction and the stress–strain behaviour are investigated on three kinds of materials which contain many twinned regions. A relaxation peak of internal friction with the activation energy (0.63 ± 0.03) eV is observed in an 89 at% manganese–copper alloy. The peak is thought to associated with the elementary process in the motion of surface dislocations (twin boundaries). Plastic flow possibly due to the motion of twinning surface dislocations is observed at relatively low stress level in this alloy. The relaxation peak is not found in gold–46.1 at% cadmium and indium–21 at% thallium alloys. Characteristics in a pseudo‐elastic flow due to the motion of twinning surface dislocations are examined on the gold–cadmium alloy.
Experimental Determination of Intrinsic Resistive Stress for Twinning Surface Dislocations
Authors: Sumino K. 
Published: July 2007

AbstractThe intrinsic resistive stress for twinning surface dislocations is determined from the analysis of the experimental results obtained in a previous paper [10]. The intrinsic resistive stress is expressed in terms of G′/G which is a ratio of the theoretical shear strength for twinning along a twin boundary to that in a perfect crystal. It is found that G′/G < 0.20 for 89 at% manganese–copper alloy and G′/G = 0.75 × 10−2 for gold–46.1 at% cadmium alloy.
X‐Ray Investigation of Lattice Deformations in Silicon Induced through High‐Energy Ion Implantation
Authors: Bonse U. , Hart M. , Schwuttke G. H. 
Published: July 2007

AbstractX‐ray interference fringes observed in X‐ray topographs of silicon crystals bombarded with high energy ions (dose > 1015 ions/cm2) are described. The X‐ray fringes are used to analyze the deformation state of the crystal. It is shown that the bombarded crystal is a special kind of bicrystal composed of a thick perfect bulk crystal topped by a thin practically perfect layer crystal. Both crystals have the same crystallographic orientation and the same lattice constant but are separated by a small rigid body displacement. Contrast and geometry of the observed X‐ray patterns agree with the theoretical patterns calculated by Bonse and Hart [1] on the basis of a layer/bulk bicrystal model, and are also supported through transmission electron microscopy results. The ion range calculated from the interference fringes is in good agreement with the experimentally determined range.
Electric Conductivity and Hall Effect in Evaporated Cadmium Selenide Films
Authors: Berger H. , Jäniche G. , Grachovskaya N. 
Published: July 2007

AbstractConductivity and Hall effect were investigated on evaporated CdSe films either non‐treated or annealed at 400 and 700°C. The measurements are performed in the temperature range from −150 to 400°C. In the lower temperature range the mobility of electrons follows an exponential temperature dependence of the form μeff = μ0 exp (– ΔE/kT) typical for polycrystalline films, which is not only determined by scattering mechanisms alone but also by the numbers and properties of potential barriers at the crystallite boundaries. These properties of polycrystalline film structure also explain the dependence of conductivity and mobility on film thickness found in non‐treated CdSe films. In the high temperature range conductivity and electron concentration strongly increase, indicating a self‐activated conductivity mechanism. The conduction electron concentration is determined here by thermal intrinsic disorder of lattice atoms.
Transport Properties of Indium Antimonide Thin Films
Authors: Berchtold K. , Huber D. 
Published: July 2007

AbstractHigh mobility InSb thin films have been prepared by the “flash” evaporation method. The films exhibit carrier mobilities greater than 1000 cm2/Vs at thicknesses of about 1000 Å. Hall measurements at various temperatures have been made. The experimental results, i.e. Hall measurements and the dependence of the mobility on film thickness, are in good agreement with the theory of transport effects, which follows from the quasi‐discrete nature of energy spectrum in thin films.
Dipolar Broadening of the NMR Spectrum of 19F in UF4
Authors: Gabuda S. P. , Falaleeva L. G. , Gagarinskii Yu. V. 
Published: July 2007

AbstractThe influence of internuclear dipole–dipole and electron–nuclear dipolar interactions on the NMR spectrum shape was examined for UF4. It is shown that only the dipolar interaction of the 19F nuclei with the magnetic moments of the U4+ ions leads to such a broad NMR spectrum in polycrystalline UF4 that there is no ground for separating it into several components corresponding to the seven nonequivalent fluorine nuclei in the UF4 structure. A certain additional broadening of the experimental spectrum may be accounted for by anisotropic hyperfine interaction, due to the transfer of the spin density from U4+ to fluorine.
Production of Vacancies and Other Defects in KBr at Low Temperatures
Authors: Comins J. D. 
Published: July 2007

AbstractThe production rate of vacancies and interstitial defects formed by ionizing radiation in KBr has been studied at low temperatures. It has been found that the large difference between the production rate of vacancies at liquid helium temperature (LHeT) and liquid nitrogen temperature (LNT) may be accounted for by a combination of thermal annealing processes, interstitial stabilizing processes, and certain additional processes requiring the action of the radiation at LNT. The increase in the production efficiency of vacancies between LHeT and LNT, as predicted by the excitonic mechanism of defect production, is not observed. Studies of the bands produced on warming a crystal irradiated at LHeT to LNT indicate that the V4‐band is the major band produced and that it is produced from the H‐band. The V4‐envelope formed during irradiations at LNT is shown to consist of the V4‐band produced as above, with the addition of bands at 266 and 306 nm.
Glide Band Broadening in Crystals
Authors: Vladimirov V. I. , Orlov A. N. , Petrov V. A. , Smirnov B. I. 
Published: July 2007

AbstractA theory of glide band broadening at the yield point in crystals of alkali halide and b.c.c. metals is presented. The glide band is assumed to broaden by double cross slip of segments of screw dislocations entering into regions near the edge of the glide band that are free from dislocations. Dislocation loops emitted by the sources created in this way expand until they are stopped by other loops in neighbouring slip planes. The shape of the glide band edge is calculated as well as its rate of broadening and the densities of mobile and stopped dislocations. These results contain no arbitrary constants and are confirmed by special experiments carried out on LiF crystals.