bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propagation of Electromagnetic Waves in a Plate‐Like Semiconductor at Nonstandard Dispersion Law of Carrier Energy
Authors: Dykman I. M. , Tomchuk P. M. , Almasov L. A. 
Published: July 2007

AbstractAn investigation is made of the propagation of electromagnetic waves through a semiconductor plate to which a constant electric field F is applied. In the case when the dispersion law of carrier energy differs from the isotropic parabolic one, a specific mechanism, depending on the energy band structure, arises which affects the complex part of the refractive index. For a dispersion law of Kane type [3] this mechanism causes additional attenuation of the wave. For a weakly anisotropic law, similar to that in p‐type germanium, it amplifies or attenuates the wave depending on the polarization. In both cases the effect increases proportional to F2. Therefore, by means of the electric field, the reflection and transmission can be influenced, and also the reflected and passed radiation can partly be polarized with varying degree of polarization. The derived formulas make it also possible to obtain additional information on the semiconductor properties, in particular the carrier temperature, from the measured reflection and transmission coefficients.
Investigation of the Heisenberg Model on the Basis of the Real Spin‐Wave Theory
Authors: Praveczki E. 
Published: July 2007

AbstractThe operator formalism of real spin‐waves is introduced. Applying this formalism to the Heisenberg model and making use of a new method of calculation, the energies of the real spin‐waves are renormalized taking into account their interactions. The formula derived for the magnetization in this way leads to better results than those derived by Tyablikov [5], Tahir‐Kheli and ter Haar [6], and in an another approximation by Callen [8].
An Analysis of the Thermodynamics of Dislocation Glide
Authors: Hirth J. P. , Nix W. D. 
Published: July 2007

AbstractA general treatment of thermally activated dislocation motion is presented following the approach first suggested by Basinski and making use of Leibniz's formula to analyze the properties of arbitrarily shaped obstacles. The small region surrounding a dislocation obstacle is shown to be an acceptable thermodynamic system with the effective stress, defined as the difference between the applied stress and the long range internal stress evaluated at the obstacle, as an appropriate thermodynamic variable. All of the thermodynamic properties of such a local system are self consistent. The question of the choice of a thermodynamic system is discussed in connection with the results of prior treatments of the problem. Whether one considers a local system using the effective stress as the operative thermodynamic variable, or the entire crystal as a system using the applied stress, the value of the effective stress and the conditions for which it is zero must be known, in general, in order to relate measured thermodynamic quantities to the properties of an obstacle. The thermodynamic methods are illustrated with the use of a simple sinusoidal model for the backstress produced by an obstacle. The difficult problem of relating the stress and temperature dependence of plastic flow to the results of thermodynamic analysis is treated. The discussion indicates that serious errors can be made either when the effective stress is not precisely known, as is commonly the case for high temperature creep, or when the stress and temperature dependence of the preexponential constant are not taken into account.
Space‐Charge‐Limited Current and Band Structure in Amorphous Organic Films
Authors: Caserta G. , Rispoli B. , Serra A. 
Published: July 2007

AbstractElectrical conduction phenomena in thin films of some organic polymers have been investigated. The current‐voltage characteristics of polymethylmetacrilate, polyvinylformal, and polyethylene‐terephthalate films display a space‐charge‐limited current (SCLC). The steady‐state SCLC and the back current are interpreted in terms of an energy band model with localized states uniformly distributed in energy within a region of the forbidden band. This region is (0.353 + 0.025) eV wide and seems to be independent of the chemical nature of the amorphous material, the sample preparation procedure, and the sample thickness. The density per unit energy of localized states ranges from 1014 to 1018 cm−3 eV−1.
The Energy Dependence of Lattice Disorder in Ion‐Implanted Silicon
Authors: Marsden D. A. , Bellavance G. R. , Davies J. A. , Martini M. , Sigmund P. 
Published: July 2007

AbstractThe energy dependence of lattice disorder has been studied by implanting bismuth ions of energy 20 to 225 keV into silicon crystals at room temperature. Implant doses have been kept below 6 × 1013 ions cm−2 to avoid approaching “saturation” disorder. Lattice disorder has been measured by means of the orientation dependence of the backscattered yield of a 1.0 MeV helium ion beam (i.e. by the “channeling” technique). Within the experimental precision, the observed disorder increases linearly with implantation energy over the whole range studied. This linear dependence is consistent with the Kinchin‐Pease equation, but its slope is at least a factor of two greater than the predicted value. Possible explanations for this discrepancy are discussed. The most reasonable one is that the disorder measured by the channeling technique includes not only the atoms that have been ejected into interstitial positions by the implantation, but also some of the lattice distortion resulting from this primary damage.
Isotope Effect and Divacancies for Self‐Diffusion in Copper
Authors: Rothman S. J. , Peterson N. L. 
Published: July 2007

AbstractThe simultaneous diffusion of 64Cu and 67Cu has been measured in copper single crystals from 890 to 1061 °C. The strength of the isotope effect f ΔK is 0.684 ± 0.014 and is independent of temperature within the experimental error. This indicates that the contribution of divacancies to self‐diffusion in copper is small. The diffusion coefficient of 67Cu in copper single crystals was measured from 700 to 1060 °C and is given by

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Spin‐Wave Relaxation in Single Crystals of Cobalt‐Substituted Nickel‐ and Nickel–Zinc Ferrite
Authors: Voigt F. , Manzel M. , Schmitz A. 
Published: July 2007

AbstractThe effect of small concentrations of substitutional cobalt ions on the spin‐wave relaxation was measured using parallel‐pumping. The cobalt contribution to the anisotropy of spin‐wave relaxation is found to be very small. The fraction of cobalt ions which contribute to the relaxation is larger than the fraction expected from the theory. The departure from the theory and the temperature behaviour suggest that the cobalt ions contribute to a direct relaxation process to the lattice.
Characteristics of Anomalous Transmission of X‐Rays in the General Case of Laue Diffraction
Authors: Kovev E. K. , Efimov O. N. , Korovin L. I. 
Published: July 2007

AbstractThe characteristics of the anomalous transmission of X‐rays for crystals without a centre of symmetry and for the unsymmetrical Laue diffraction are obtained on the basis of the dynamical theory of scattering by a perfect absorbing crystal. The characteristics are connected with the real and the imaginary parts of the structure factor and with the geometry of the experiment. The characteristics suggest a possibility to use them for the investigation of the crystals with different types of defects.
Electrical Conductivity of Single Crystalline Nickel Oxide
Authors: Eror N. G. , Wagner J. B. 
Published: July 2007

AbstractThe electrical conductivity of single crystalline NiO was found to be proportional to the 1/4 power of the oxygen pressure for oxygen partial pressures between 100and 10−4atm over the temperature range of 900 to 1200 °C. These results are in agreement with singly ionized cation vacancies as the predominant nonstoichiometric defect. The sum of the enthalpies of formation of nonstoichiometric disorder and activated enthalpy of movement of an electron hole was found to remain constant when thermodynamic equilibrium was maintained. The activated enthalpy of movement of an electron hole, however, was found to obey the “Meyer‐Neldel” relationship, that is, it increased as the concentration of electron holes decreased. An argument has been offered for the explanation of the “Meyer‐Neldel” rule. This explanation involves consideration of another equilibrium between free electron holes and those trapped at imperfections (such as dislocations) which are not usually considered in the usual theory of point defects in nonstoichiometric compounds.
Gestörte Diffusion von Tritium in einer Silber‐Lithium‐Legierung nach Neutronenbestrahlung. Edelgase (und Wasserstoffisotope) in Festkörpern 44
Authors: Migge H. 
Published: July 2007

AbstractEs wurde die Abgabe von Tritium aus einer Ag–20 At% Li‐Legierung im Bereich zwischen 280 und 600 °C nach Neutronenbestrahlung gemessen. Die Diffusionskoeffizienten weisen unterhalb von 390 °C eine größere Temperaturabhängigkeit auf als oberhalb (Aktivierungsenergien 1,3 bzw. 0,49 eV). Bei Erhöhung der Neutronendosis von 3,6 × 1016/cm2 auf 1,3 × 1017/cm2 wird die Temperaturabhängigkeit in beiden Temperaturbereichen größer (2,34 bzw. 1,14 eV), und die Diffusionskoeffizienten werden deutlich kleiner. Es tritt im gesamten Temperaturbereich zu Beginn ein Anlaufvorgang auf. Aus dem Anlauf wird eine Zeitkonstante b [s−1] für den Austritt der Tritiumatome aus Fallen bestimmt. Die Aktivierungsenergie und der Vorfaktor von b sind praktisch unabhängig von der Neutronendosis.
Band Structure and Nature of Lattice Defects in GeTe from Analysis of Electrical Properties
Authors: Lewis J. E. 
Published: July 2007

AbstractThe measured transport properties of non‐stoichiometric GeTe have been satisfactorily analysed on the basis of a two‐carrier model and the various band parameters have been evaluated. In particular the variation of the carrier density of the system with composition has been obtained and then compared to the total number of excess atoms in the non‐stoichiometric lattice. It is found that the defects occurring in GeTe due to these excess atoms are of a complex nature, except for compositions close to stoichiometry where singly ionized vacancies are the dominant defect.
Diffusion Length and Lifetime of Triplet Excitons and Crystal Absorption Coefficient in Tetracene Determined from Photocurrent Measurements
Authors: Vaubel G. , Kallmann H. 
Published: July 2007

AbstractBy comparing the decrease of the i+ and i− currents as function of the exciting wavelength and from the maximum of the i− current the crystal absorption coefficient of tetracene can be determined. With the penetration depth of the radiation thus known the diffusion length and lifetime of triplet excitons are determined from the dependence of the currents on the wavelengths. The diffusion length is found to be (0.4 ± 0.2) μm, the lifetime about 100 μs.
Mössbauer Studies of Tin 119m Recoil Atoms in Some Mixed Oxides of Tin. I. The Nature of the Recoil Effects in Mg2SnO4
Authors: Hannaford P. , Wignall J. W. G. 
Published: July 2007

AbstractThe Mössbauer spectrum emitted following thermal neutron irradiation of the spinel Mg2Sn118O4 displays a subsidiary line which can be associated with Sn119m recoil atoms at abnormal sites in the crystal. The isomer shift and (unresolved) quadrupole splitting of this line suggest that it originates from divalent tin ions in which there is an admixture of 5p‐electrons having predominantly pz‐character. The temperature dependence of the Mössbauer fraction indicates a weak average binding which, according to the computed intensities of the quadrupole doublet, may result from a large 〈z2〉 along the principal axis of the electric field gradient. Isochronal and isothermal annealing data indicate that the defect line disappears irreversibly above 600 °C and that the annealing processes are distributed over a fairly narrow band of activation energies in the range 3 to 4 eV. These results are interpreted in terms of a defect complex comprising a divalent tin ion and an associated charge‐compensating oxygen vacancy.
EPR of Cr3+ Ions in Alexandrite
Authors: Barry W. R. , Troup G. J. 
Published: July 2007

AbstractResults on the EPR of Cr3+ ions occupying mirror symmetry sites in alexandrite are described. The Spin Hamiltonian parameters are: D = ( −7.31 ± 0.02) GHz, E = = (‐1.71 ± 0.02) GHz with gx = 1.978 ± 0.003, gy = 1.980 ± 0.004, gz = 1.969 ± ± 0.004 with a corresponding zero‐field splitting between the Kramer's doublets of (15.7 ± 0.05) GHz. The relationships between the crystallographic axes and the axes of the magnetic complexes show slight departures from the crystallographic symmetry of pure chrysoberyl.
Sulphur Diffusion in Copper: Departure from the Arrhenius Plot
Authors: Moya F. , Moya‐Gontier G. E. , Cabane‐Brouty F. 
Published: July 2007

AbstractA study is made of sulphur diffusion in copper single crystals using 35S between 550 and 1000 °C. The plot log D = f(1/T) was not a straight line. Different models were examined to explain the departure from linearity in the Arrhenius plot. A simple model is proposed, basing on classical mechanisms: monovacancy diffusion and diffusion along randomly distributed dislocations. For T > 800 °C, Q = 2.14 eV, and D0 = 23 cm2 s−1, the unusually high diffusion coefficients do not agree well with the value of Q, similar to that of self diffusion. For T < 800 °C, the dislocation model gives a binding energy of some tenths of an electron‐volt.
On One of the Possible Mechanisms of Formation of Induced Anisotropy in Ferromagnetic Films
Authors: Lesnik A. G. 
Published: July 2007

AbstractWith the assumption that the concentration of nonmagnetic inclusions (lattice defects, impurity atoms, oxides) is higher at the grain boundary than inside the grain, a steady state distribution of inclusions is determined along the grain boundary in a ferromagnetic film. It appears to be nonuniform since inclusions leave those boundary sections where the jump of the normal component of magnetization at the boundary is maximum and go into sections where the jump is minimum. Nonuniformity of the inclusion distribution at the boundary results in a magnetic anisotropy. Expressions are derived for the anisotropy energy. The numerical evaluation shows that the experimental value of anisotropy energy is obtained by such a mechanism in the case when inclusions decrease strongly the magnetization of the boundaries.
Calculations of the Contrasts of Moiré Patterns from Twisted Lattices by the Dynamical Theory of Electron Diffraction
Authors: Izui K. , Nishida T. 
Published: July 2007

AbstractCalculations are made of electron microscope image contrasts of moiré patterns from twisted lattices by using the dynamical theory of electron diffraction. The distinctions between the image profiles for a twisted crystal and those for two superposed crystals are presented. The influences of various factors such as the way of twisting, the deviation from the Bragg diffraction condition, the absorption parameters and crystal thickness on the image profiles of the twisted lattices are clarified for some specified cases.
Étude en microscopie électronique d'un alliage possédant une surstructure à longue période: Ag3Mg
Authors: Vanderschaeve G. 
Published: July 2007

AbstractLes différents défauts résultant des processus d'ordre dans l'alliage Ag3Mg sont étudiés en microscopie électronique. La nature cristallographique de ces interfaces, ainsi que les différents types de contraste auxquels elles donnent lieu sont discutés et les preuves expérimentales sont présentées.
ESR Studies of Covalency Effects between Cu2+ and Chalcogen Ions in AgCl Crystals
Authors: Schwarz D. 
Published: July 2007

AbstractAfter irradiation in AgCl crystals doped with Cu and Se or S, respectively, an ESR spectrum of a Cu2+ ion is observed the octahedral chlorine environment of which is distorted by a Se2− or S2− ion. The centre has [100] tetragonal symmetry and a essentially |3 z2‐r2 > ground state. The superhyperfine structure in AgCl: 77Se, Cu indicates a strong interaction with one selenium nucleus. If σ‐bonding is assumed the magnitude of the covalency between the Cu2+ and the Se2− ion can be estimated: the hole spends about 20% of its time in a pz state of the Se2−. From the existence of this covalent bonding in the paramagnetic complex follows that the spin‐orbit coupling is more reduced in [Cu2+ Se2−] than in [Cu2+ S2−].
Negative Resistance in GaS Single Crystals
Authors: Romeo N. 
Published: July 2007

AbstractThe I‐U characteristic of GaS single crystals has four distinct zones: a low‐voltage zone which is ohmic, a zone in which the current depends on the voltage by a relationship of the I ∝ U2 type, a third zone in which the slope of the characteristic is very sharp and current pulses are present and a fourth in which the characteristic is negative. Experimental findings have led us to suppose that this behaviour of GaS can be explained by Lampert's theory of negative resistance in insulators.
Shallow States in Semiconductors by Impurity Model Potential Method
Authors: Jaroš M. 
Published: July 2007

AbstractA impurity model potential is constructed using the method of Heine et al. The treatment of the short‐range forces in this method is refined making the theory applicable to the impurity problem. It is shown how a simple spherical screened model potential can be used for the ground state calculation of shallow donors in semiconductors; the ionization energies of P, As, and Sb in silicon are given.
Ein Diffusionsmodell zur Behandlung der Doppelkinkrelaxation in kubisch‐flächenzentrierten Metallen
Authors: Engelke H. 
Published: July 2007

AbstractDas Seegersche Modell der Doppelkinkrelaxation wird erweitert mit dem Ziel, die sogenannten sekundären Eigenschaften der Bordoni‐Maxima in k.f.z. Metallen zu deuten. Eine Untersuchung der Eigenschaften von Versetzungsbögen im Peierls‐Potential ergibt, daß auf jedem Bogen nur ein Kinkpaar explizit zu berücksichtigen ist. Kinkbildung und Kinkdiffusion werden einheitlich mit Hilfe der von Kramers und Brinkman für chemische Reaktionen abgeleiteten Diffusionstheorie beschrieben. In zwei Näherungsschritten wird ein Mehrmuldenmodell für die Bogenbewegung im Peierls‐Potential abgeleitet. Die auftretenden Relaxationszeiten weisen eine Abhängigkeit von der Bogenlänge auf, welche in qualitativer Übereinstimmung mit den Dämpfungsmessungen ist.
Fine Structure of the “One‐Dimensional” Exciton in Germanium in Parallel Magnetic and Electric Fields
Authors: Seysyan R. P. , Zakharchenya B. P. 
Published: July 2007

AbstractThe excited states of a one‐dimensional exciton in finite magnetic fields represent doublets consisting of even and odd components. The differential electroabsorption technique was used to observe transitions to odd states of the one‐dimensional exciton in germanium in parallel magnetic and electric fields. An analysis of the differential electroabsorption spectrum in parallel magnetic and electric fields is given.
Dichroïsme circulaire magnétique et absorption de I'ion Nd3+ dans CaWO4
Authors: Boccara A. C. , Ferré J. , Badoz J. 
Published: July 2007

AbstractOn étudie les spectres de dichroïsme circulaire magnétique et d'absorption en lumière polarisée d'un cristal CaWO4:Nd3+ dans le visible et le proche infra‐rouge, à plusieurs températures. Cette étude permet de déterminer expérimentalement un grand nombre de facteurs de Landé des états excités. Ces résultats sont comparés à ceux obtenus à partir de la théorie du champ cristallin.
Temperature Change Experiments during Secondary Creep of the Intermetallic Compound MgZn2
Authors: Hinz D. , Paufler P. , Schulze G. E. R. 
Published: July 2007

AbstractFrom temperature change experiments (between 260 and 435°C) during secondary creep of the intermetallic compound MgZn2 an activation enthalpy ΔH = (2.25 ± 0.20) eV for basal slip has been derived. The shear strain rate γ can best be described by the empirical relation γ = 7 × 1011 s−1 × τ5.5 ± 1.0 exp (‐ ΔH/kT) where τ is the applied shear stress. X‐ray topographies show the formation of low angle boundaries during steady‐state creep.
Kinetics of Clustering under Vacancy Annealing
Authors: Srinivasan N. K. , Ramachandran V. 
Published: July 2007

AbstractAn equation is derived for the total vacancy concentration in quenched alloys containing impurities under the condition of free vacancies annealing by migration to fixed sinks. The time to reach maximum in resistivity in isothermal aging experiments need correction if the total vacancy concentration which decays exponentially after the transients has a small time constant. A procedure for this correction is outlined.
Influence of Resonance Transfer and Exciton Diffusion on Luminescence Decay
Authors: Swenberg C. E. , Stacy W. T. 
Published: July 2007

AbstractTheoretical equations are formulated to describe the luminescence decay of donors and acceptors including both the effects of exciton diffusion and resonance energy transfer. Closed form expressions for the population and decay of excited donors and acceptors are developed using the Padé approximant method with the diffusion coefficient as an expansion parameter. Possible experiments are suggested.
Effect of Channeling on Damage Rates Associated with Heavy‐Ion Irradiation of Gold
Authors: Noggle T. S. , Barrett J. H. 
Published: July 2007

AbstractElectron microscope studies of radiation damage produced by 60‐MeV iodine ions in thin gold crystals have been made to determine the dependence of damage rate on orientation of the ion beam relative to [011] and (111). Experimental values of the minimum damage rates and half‐widths were compared with calculations made with a Monte Carlo computer program using either the Thomas‐Fermi or the Bohr potential and incorporating thermal vibrations. The thermal vibrations were found to be necessary for agreement with experiment, and agreement was better with the Thomas‐Fermi potential than with the Bohr. Experimental observations by a stereo technique gave a tentative confirmation of a calculated depth dependence and showed in addition a deficiency of damage clusters near the surface.
Ultra‐Violet Excited Paramagnetic Centres in Calcium Tungstate
Authors: Sayer M. , Lynch G. F. 
Published: July 2007

AbstractTwo sets of paramagnetic species having a spectroscopic splitting factor slightly higher than the free electron value are produced in CaWO4 doped with copper after irradiating the crystal with ultra‐violet light. One set of lines is identified as being due to a hole trapped at a single tungsten site and is found to bleach out on warming the crystal through the thermoluminescence glow peak at 160 °K. The other set of lines increases in intensity first with the emission of light in the 160 °K peak and then again with the 260 °K peak and bleaches out on heating the crystal through the thermoluminescence glow peak at 400°K. The copper does not take part in the excitation process directly. It is suggested that the low temperature paramagnetic species arises from the loss of an electron from the tungstate complex.
Electronic Structure of PbS, PbSe, and PbTe
Authors: Overhof H. , Rössler U. 
Published: July 2007

AbstractThe electronic band structures of PbS, PbSe, and PbTe have been calculated using the relativistic Green's function method. The choice of a relativistic atomic potential for Pb and of nonrelativistic atomic potentials for S, Se, and Te inthe muffin‐tin spheres results in similar band models for the lead salts. Thus a nearly uniform interpretation of experimental data for these materials can be presented. A good agreement of calculated band separations with results from reflectivity, electroreflectance, and photoemission measurements is achieved.