bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Efficiency of Dislocation Climb in Gold
Authors: Seidman D. N. , Balluffi R. W.
Published: July 2007

The climb rate of the three‐dimensional dislocation network in gold is investigated experimentally under the following non‐equilibrium vacancy conditions: 1) supersaturation at elevated temperatures during rapid down‐quenching; 2) supersaturation at lower temperatures following a rapid down‐quench from an elevated temperature; 3) subsaturation during uppulsing and holding at an elevated temperature. It is found that the network climbs with a quite high efficiency under all the above conditions; that is, at a rate which is within a factor of one‐tenth to one of the maximum possible rate calculated on the assumption that vacancy equilibrium is maintained evergwhere along the dislocation cores and that the climb rate is therefore vacancy diffusion limited.
Technique for Measuring the Rate of Growth of Crystals from Solutions in Dependence on the Degree of Supersaturation at Low Supersaturations
Authors: Bennema P.
Published: July 2007

A technique is developed for the accurate measurement of the rate of growth R of one type of crystallographic face as a function of the relative supersaturation (σ) for low values of R and σ [1]. The growing crystal is suspended from the arm of a balance and hangs in a closed supersaturated solution. The weight of the crystal and the temperature of the supersaturated solution can thus be measured simultaneously. From numerous results taken at different times the (R, σ) relation can be obtained numerically.
The Effect of Dislocation Dipoles on the Shape of the Nuclear Magnetic Resonance Line
Authors: Greenberg B. A.
Published: July 2007

The effect of dislocation dipoles on the broadening of a NMR line is studied. The shape of the satellite line is determined. The line width is obtained as a function of the dipole concentration, the dipole length and the relative orientation of the dipole and the external constant magnetic field. The shape of the central line is also determined. The shape function of the central line is presented for certain relative orientations of the dipole and the magnetic field.
On the Theory of Free Carrier Electro‐Magneto‐Optical Phenomena
Authors: Kołodziejczak J. , Stramska H.
Published: July 2007

The nonlinear Boltzmann equation is discussed for nonspherical and nonparabolic energy bands assuming strong dc and weak ac electric fields. The current density is calculated in the limit of a quadratic deviation from Ohm's law. Freecarrier magneto‐optical phenomena in the presence of a strong dc electric field are discussed.
Anordnungen paralleler Versetzungen in anisotropen Medien
Authors: Seeger A. , Wobser G.
Published: July 2007

Für zwei parallel laufende, geradlinige Versetzungen im kubisch‐flächenzentrierten bzw. hexagonal dichtestgepackten Gitter, die sich auf zwei parallelen dichtestgepackten Ebenen bewegen, werden die stabilen Konfigurationen ermittelt. Dabei werden alle möglichen Kombinationen von Burgersvektoren in 〈110〉‐ bzw. 〈2110〉‐Richtungen, also nicht nur sogenannte Versetzungsdipole, in Betracht gezogen. Die Rechnungen werden unter Berücksichtigung der elastischen Anisotropie (im Fall des kubischen Gitters für Versetzungen in 〈110〉‐oder 〈211〉‐Richtungen) durchgeführt. Für eine Reihe von Metallen sowie Ge und Si werden die stabilen Gleichgewichtskonfigurationen sowie die zum Aufbrechen derselben benötigten Kräfte angegeben. Im Anhang werden die mit der anisotropen Elastizitätstheorie berechneten Spannungskomponenten für Versetzungen in 〈110〉‐ und 〈211〉‐Richtungen in kubischen Kristallen sowie für Versetzungen in der hexagonalen Basisebene zusammengefaßt. Die in diesen Gleichungen auftretenden Materialkonstanten werden in Tabellenform angegeben.
Berechnung des Debye‐Waller‐Faktors von Nickel
Authors: Gleiss R.
Published: July 2007

Es ist das Ziel dieser Arbeit eine einfache Methode anzugeben um den Debye‐Waller‐Faktor f für Nickel auszurechnen. Dazu wird von der harmonischen Gittertheorie ausgegangen. Sie liefert eine einfache Formel für f, die sich für hohe und tiefe Temperaturen in eine Reihe entwickeln läßt. In dieser treten die Momente des Schwingungsspektrums auf und Konstanten, die mit der spezifischen Wärme C zusammenhängen. Die Momente werden aus gemessenen Frequenzspektren und aus Rechnungen über ein 2‐Nachbar‐Gitter‐Modell ermittelt. Man kann sie aber auch aus der experimentell bestimmten Temperaturabhängigkeit von C erhalten. Die so berechneten f(T)‐Werte stimmen im Rahmen der Meßgenauigkeit gut mit dem Experiment überein. Die Methode läßt sich auch auf andere kubische Kristalle anwenden.
The LCAO Method for an Arbitrary Mixture of Atoms
Authors: Gubanov A. I.
Published: July 2007

A new method for quantum‐mechanical calculations for electrons in a disordered mixture of atoms is proposed. This method is based on the linear combinations of atomic orbitals and uses the binary distribution function of atoms. To restrict the number of equations a finite number of atoms is chosen and an averaging over the configurations and types of atoms is performed. This method can be used to calculate the energy spectrum and wavefunctions of electrons in liquid and amorphous semiconductors, as well as in liquid and solid disordered alloys.
On the Conduction Mechanism in Uranium Dioxide
Authors: Devreese J. , De Coninck R. , Pollak H.
Published: July 2007

Experimental data on the thermoelectric power and electrical conductivity of nearly stoichiometric UO2+x single crystals are presented and analysed in order to estimate the activation energy of the drift mobility. These results are compared with the predictions of small polaron theory. Although some further analysis is required, there is evidence that conduction in UO2+x occurs via a hopping mechanism.
Tunnelling in a two‐band model superconductor
Authors: Radhakrishnan V.
Published: July 2007

The Josephson and ordinary tunnelling currents are evaluated for two‐band model superconductors. Numerical calculations of these currents are made for a niobium‐tin junction, for which this model is applicable, and compared with experiments.
Interpretation of the temperature dependence of Ag+ dipole strengths in alkali halides
Authors: Dreybrodt W. , Fussgaenger K.
Published: July 2007

The absorption spectrum of Ag+ doped RbCl is measured at various low temperatures in the spectral range from 6.4 to 5.0 eV. The temperature dependence of the Ag+ dipole strength in RbCl is different from that found in NaCl, KCl, and KBr. The different temperature behaviours are interpreted as being due to the different lattice potentials seen by the Ag+ in the various host crystals. The static potentials for Ag+ in the crystals are calculated by a semiphenomenological method. For NaCl, KCl, and KBr a potential minimum is found at the symmetry centre. For RbCl, however, a potential barrier exists at the symmetry centre and potential minima occur at 0.25 Å away from the centre in the [111] direction.
Properties of the B‐centre in additively coloured Ag+ doped KCl crystals
Authors: Degrieck W. , Jacobs G.
Published: July 2007

Additively coloured silver‐doped KCl single crystals grown from highly purified material are examined. A method is developed for obtaining crystals containing only B‐centres. This investigation reveals the presence of two components in the so‐called B band. Several experiments contradict the theory that B‐centres comprise a Ag+ ion associated with an F‐centre. Irradiation at higher temperatures gives rise to a series of new absorption bands. The rate of formation of these bands is greatly affected by the presence of vacancies. By an appropriate thermal treatment the new bands can be bleached and the original B absorption restored.
Diffusion of tritium from lithium fluoride
Authors: Matzke Hj.
Published: July 2007

The release of tritium from neutron irradiated LiF single crystals (5.4 × 1016 nvt, at approximately 300 °C) follows the relation D = 6 exp (−38800/RT) cm2s−1 between 500 °C and the melting point. Volume diffusion kinetics are obtained from isothermal experiments. The tritium diffusion is found to be essentially independent of the neutron dose (3 × 1016 to 3 × 1017 nvt) and nominal temperature during irradiation (−80 to 200 °C). Data obtained following ion bombardment confirm these results.
The fine structure of spots in electron diffraction resulting from the presence of planar interfaces and dislocations
Authors: Gevers R. , van Landuyt J. , Amelinckx S.
Published: July 2007

A theory is developed which accounts for the fine structure of electron diffraction spots due to the presence of imperfections of different types in thin foils. The method consists essentially of considering the diffraction pattern to result from the image (i.e. from the amplitudes of transmitted and scattered beams at the exit surface of the foil) by Fourier transformation. The image is described by the expressions given by the two‐beam column approximation assuming the symmetrical Laue case to be realized. The use of the method for the present problem is justified. The geometry of the fine structure and the intensities of the different components of the transmitted and scattered beams are then calculated for a general planar interface taking anomalous absorption into account in the usual phenomenological way. A detailed discussion is given for the special case of a stacking fault. In particular the relation between the properties of the fringe patterns and the fine structure of the transmitted and scattered beams is emphasized. In part II observations will be reported on crystals containing stacking faults which lend support to the theory developed here. In part III crystals containing domain boundaries will be discussed and part IV will be devoted to the study of the diffraction effects of other types of geometrical imperfections.
Beitrag zur Widerstandsmessung von nn+‐ und pp+‐Epitaxialschichten nach dem Durchbruchsverfahren
Authors: Frank H.
Published: July 2007

Nach kurzer Übersicht über die wichtigsten zerstörungsfreien Meßmethoden zur Bestimmung des spezifischen Widerstandes von Epitaxialschichten wird eine verbesserte Elektrodenanordnung des Durchbruchsverfahrens für einen einfachen Halbleiter‐Metall‐Spitzenkontakt angegeben. Die empirisch ermittelte Eichkurve wird für den Fall der dicken Sperrschicht auf Grund eines einfachen Modells nach der Schottky'schen Sperrschichttheorie begründet. Das Ergebnis zeigt, daß bei geeigneter Wahl zweier Parameter eine befriedigende Übereinstimmung zwischen empirischer und theoretischer Eichkurve für Widerstände größer als 0,1 Ωcm bei Si, Ge und GaAs erzielt werden kann. Bei Widerständen unter 0,1 Ωcm wird für den Fall der dünnen Sperrschicht an n‐GaAs empirisch festgestellt, daß die in der Sperrschicht bei Spannungsdurchbruch auftretende Leistung bezogen auf die mittlere freie Weglänge konstant ist. Aus dieser Beziehung folgt, daß die Durchbruchsspannung der Trägerbeweglichkeit und der dritten Wurzel des spezifischen Widerstandes proportional ist. Die Übereinstimmung mit den Meßwerten an GaAs, Si und Ge im Bereich niedrigen spezifischen Widerstandes ist sehr gut.
Photoluminescence of GaAs0.7P0.3
Authors: Tuck B.
Published: July 2007

The fluorescence of n‐ and p‐type GaAs0.7P0.3 under conditions of optical excitation is described. Measurements were made at 300 and 77 °K. In the as‐grown state the crystals were n‐type. They were made p‐type by diffusing in zinc and comparison was made between the fluorescence of the n‐ and p‐type specimens. At 77 °K, low‐energy spectral lines were found in the p‐type specimens in addition to that due to recombination via the zinc centre. One of these has an intensity which depends on the position of the Fermi level. Another of them appears to be associated with the presence of arsenic vacancies.
Photoconductivity and drift mobilities in single crystal realgar (As4S4)
Authors: Street G. B. , Gill W. D.
Published: July 2007

The photoconductivity and carrier mobilities of synthetic crystals of realgar (As4S4) have been investigated. A sharp increase in the photoresponse at short wavelengths is attributed to an energy gap of (2.40 ± 0.05) eV. An additional weak peak in the photoresponse at 600 nm is due to free hole formation at defect or impurity sites. Electron and hole mobilities have been measured over the temperature range from 250 to 470 °K. At 25 °C the hole mobility was 12 cm2V−1s−1 and the electron mobility 2 × 10−2 cm2V−1s−1. The hole transport can be described by band conduction controlled by lattice scattering. The electron changes is consistent with an intermolecular hopping process which at low temperatures transport to a trap‐controlled mechanism.
Quantum theory of the electrical conductivity of semiconductors with a non‐standard energy band
Authors: Askerov B. M. , Gashimzade F. M.
Published: July 2007

The theory developed by Adams and Holstein is generalized to the case of an isotropic but non‐parabolic energy band, such as the conduction band in InSb. The problem of the electron spectrum in crossed electric and magnetic fields is solved taking into account all the interactions of the conduction band with the valence bands. It is shown that in this case, as for a parabolic band, an electric field appears in the spectrum within the linear approximation. The solution of the equation of motion for the density matrix shows that the non‐parabolicity enters into the dissipative current only through the energy conservation law or the scattering process. The general formula for the electrical conductivity tensor is applied to degenerate semiconductors; Shubnikov‐de‐Haas oscillation conditions are obtained when spin splitting of the Landau levels is considered and the positions of the oscillation maxima are calculated. Inelastic electron scattering by optical phonons is also considered. The conditions for magnetophonon resonance in semiconductors with non‐parabolic energy bands are derived. It is demonstrated that all the maxima of Gurevich‐Firsov oscillations except the first have the natural width.
Die Ausläuferabsorption chalkogendotierter AgBr‐Kristalle bei variabler Fremdkationenkonzentration
Authors: Schwarz D.
Published: July 2007

Durch den Einbau zweiwertiger Fremdkationen in AgBr‐Kristalle, die bereits zweiwertige Fremdanionen enthalten, wird die der Eigenabsorption langwellig vorgelagerte Ausläuferabsorption beeinflußt. Bei −190 °C besitzt diese Ausläuferabsorption eine Bandenstruktur. Falls die Kationenkonzentration hinreichend klein ist, wird eine Erhöhung der Ausläuferbande festgestellt. Die Deutung dieser Messungen gelingt mit der schon früher verwendeten Modellvorstellung über die Struktur der absorbierenden Zentren; dem zweifach negativen Chalkogenion auf Anionengitterplatz sowie der Annahme von Frenkel‐ und Schottkyfehlordnung.
On the mechanism of lattice electromigration in metals
Authors: Klotsman S. M. , Timofeev A. N. , Trakhtenberg I. Sh.
Published: July 2007

Values of the “residual resistivity” B for ions of silver diffused into copper and gold over a temperature range above 0,8 Tm are calculated on the basis of data taken from a previous paper of Archipova, Klotsman, Timofeev, and Trakhtenberg [1]. These values of B are compared with values of the residual resistivity for substitution and interstitial impurity ions in group I noble metals. This shows that scattering by the diffused ions occupying interstitial positions gives the main contribution to the driving force of the activated complex. The observed temperature dependence of B and the order of magnitude of the temperature coefficients (B−1 ∂B/∂T ≈ 10−4 deg−1) can be explained by the interaction of impurity ions in interstitial positions with the surrounding lattice. As a first approximation this interaction can be considered as a mutual deformation of the impurity ion and the lattice. Using this approximation it is possible to estimate the magnitude of B for impurities from various parts of the periodic table in a given lattice.
Magnon Contribution to the Low‐Temperature Specific Heat of UO2
Authors: De Batist R. , Gevers R. , Verschueren M.
Published: July 2007

The contribution of acoustical phonons to the low‐temperature specific heat of UO2, as calculated from the single crystal elastic constants, is much too small to account for the observed heat capacity. It is shown here that this data can however be explained in terms of antiferromagnetic magnons. An expression for the heat capacity due to spin waves is derived, firstly for a simple antiferromagnet having a spherically symmetric dispersion relation, and secondly for UO2, where the dispersion relation is cylindrically symmetrie. For UO2 it is found that the next nearest neighbour interactions must be included in order to obtain a meaningful dispersion relation.
A Zener‐Damping Peak in Fe‐4 Wt% Si
Authors: Boesono Ir. , Ernst G. J. , Lemmens M. C. , van Langen M. J. , De Vries G.
Published: July 2007

The internal friction of a 4% SiFe alloy is measured in the region 400 to 700°C using single crystal specimens. A Zener peak is found in this temperature range. The results for the relaxation time τ = τ0 exp [Q/RT] are: τ0 = 8 × 10−20±0.6 s; Q = (69±2.5) × 103cal/mol for the [100] direction; τ0 = 1.7 × 10−19±0.3 s, Q = (69±1.5) × 103 cal/mol for the [111] direction.
Adiabatic, Isothermal, and Intermediate Pressure Derivatives of the Elastic Constants for Cubic Symmetry. I. Basic Formulae
Authors: Barsch G. R.
Published: July 2007

The thermodynamic relations between the adiabatic pressure derivatives of the adiabatic elastic constants, the isothermal pressure derivatives of the isothermal elastic constants, and the isothermal pressure derivatives of the adiabatic elastic constants that can be measured ultrasonically are compiled and correctly proved for cubic symmetry. Also, the corresponding relations between the linear combinations of the third‐order elastic constants that can be determined from these pressure coefficients are derived.
Unstable Dislocations in Anisotropic Crystals
Authors: Head A. K.
Published: July 2007

In an elastically anisotropic crystal, the energy of a dislocation depends on the crystallographic direction of the dislocation line. A straight dislocation which is in a high energy direction may be unstable with its energy decreasing if it changes to a zig‐zag shape. The relation between two different criteria of instability is clarified. The theory is used to examine seven possible slip systems in three metals. Instabilities are predicted for six systems in β‐brass, two in iron, and none in niobium. Tables are given of the predicted instabilities for the 〈110〉 {111} f.c.c. system and the 〈111〉 {110} b.c.c. system for a range of elastic constants. A preliminary report is given of the observation of this phenomenon in β‐brass.
Thermal Oxidation of Silicon: Growth Mechanism and Interface Properties
Authors: Revesz A. G.
Published: July 2007

The thermal oxidation of silicon is controlled by impurities, most likely Na and/or OH (as originating from H2O or H2). The latter is the main participant under very clean conditions. In situ cleaning, oxidation, and annealing of silicon results in a SiSiO2 interface that is essentially free of surface states and shows no interface instability effects. Some of the impurities responsible for the oxide growth also contribute to ion migration through the oxide under bias at elevated temperature. The extent of this ion migration is generally very small for specimens processed by this in situ technique.
Temperature and Strain Rate Dependence of the Flow Stress in Molybdenum
Authors: Guiu F.
Published: July 2007

The effect of orientation on the temperature and strain rate ependence of the flow stress of molybdenum single crystals is investigated over the temperature range from 195 to 413°K. The values of the activation parameters ΔH, w, and v are calculated assuming that a single mechanism is rate controlling. It is found that the activation volume at constant stress is a function of the temperature. This together with other results suggest that the deformation is controlled by more than one thermally activated mechanism. An explanation is proposed based on both the overcoming of the Peierls barrier, and the non‐conservative movement of jogs in screw dislocations. The results also indicated that in the range of temperatures from 300 to 350°K there is a change in the rate controlling deformation process.
Contributions to the Mechanism of the Procopiu and Inverse Wiedemann Effects
Authors: Rothenstein B. F. , Policec A. , Anghel C. , Lupulescu M.
Published: July 2007

A study is made of the form of the electromotive force induced by the Procopiu effect or by the inverse Wiedemann effect in a search coil surrounding the ferromagnetic specimen. This provides information regarding the relative positions of the specimen axis and easy axis, and the torsion of the specimen.
Free Carrier Electro‐Magneto‐Optical Phenomena in Semiconductors
Authors: Kołodziejczak J. , Kierzek‐Pecold E.
Published: July 2007

Calculations are made of free carrier magneto‐optical phenomena in the presence of an external d.c. electric field assuming a quadratic deviation from Ohm's law. The calculations are based on the assumption of non‐parabolic energy bands with spherical symmetry. Expressions are obtained for the Faraday effect, and the Voigt effect in a d.c. electric field as well as for the electro‐optical Kerr effect in a magnetic field.
Verformungs‐ und Temperaturabhängigkeit der Magnetisierungsprozesse in Nickeleinkristallen II. Blochwandverschiebungen und Drehungen der spontanen Magnetisierung in 〈001〉‐Nickeleinkristallen
Authors: Köster E.
Published: July 2007

Die Magnetisierung und die magnetostriktive Längenänderung stabförmiger Nickeleinkristalle mit <001>‐Achsenrichtung wurden in Abhängigkeit von der plastischen Verformung und der Temperatur gemessen. In kleinen Feldern erfolgt die Magnetisierung gleichzeitig durch Wandverschiebungen und Drehungen; Magnetisierung und Längenänderung werden durch das Rayleigh‐Gesetz beschrieben. Der Anteil der Wandverschiebungen an der Anfangssuszeptibilität ist proportional zu (τ – τ0)−1, der der Drehungen ist proportional zu (τ – τ0)−2 und macht etwa 15 bis 30% der Gesamtsuszeptibilität aus. Hierbei ist (τ – τ0) die Verfestigung der Kristalle. Aus den Messungen kann die Spannungsanisotropie bestimmt werden, die eine Aussage über die Versetzungsanordnung zuläßt. In der Arbeit werden weiter die Ergebnisse aus Untersuchungen irreversibler Magnetisierungsprozesse entlang der ganzen Magnetisierungskurve mitgeteilt.
Wechselwirkung zwischen Versetzungen und ebenen Blochwänden mit starrem Magnetisierungsverlauf
Authors: Pfeffer K. ‐H.
Published: July 2007

Mit Hilfe der Peach‐Koehlerschen Formel werden die Wechselwirkungskräfte zwischen 180°‐Blochwänden, deren Magnetisierungsverlauf als starr angenommen wird, und verschiedenen Versetzungskonfigurationen berechnet. Numerische Ergebnisse werden für die (110)‐ und (112)‐180°‐Blochwände in Nickel und für die (001)‐ und (110)‐180°‐Blochwände in Eisen angegeben. Die Temperaturabhängigkeit der für die verschiedenen Versetzungskonfigurationen charakteristischen effektiven Wechselwirkungslängen und die in der statistischen Analyse der Blochwandbewegung zu beachtenden geometrisch‐statistischen Parameter werden diskutiert.
Preferred Orientation and Domain Structure of Iron Films Deposited on (100) Copper Substrates
Authors: Jones G. A.
Published: July 2007

Thin films of iron are deposited both by electroplating and by evaporation, on (100) foils of copper. They display a well‐defined preferred texture with (110) planes parallel to the substrate. The shape, orientation, and size of the grains are discussed. Magnetic observations of the domain structure using electron microscopy show that the layers are effectively biaxial. Near thicknesses of 500 Å cross‐tie walls appear, which is in accordance with energy considerations. Finally, torque measurements lead to a value for K1.
A disorder model of melting and melts
Authors: Eckstein B.
Published: July 2007

Various thermal properties of molten metals are calculated assuming a strong correspondence between the crystal and the melt. Thus, the properties of melts are composed of a “lattice dependent” term, essentially equal to the value of the property for the crystal at its melting point, and a “defect dependent” term, calculable from the theory of crystal defects. The defect concentration in the melt is estimated from the volume increase due to melting. The calculated values agree fairly well with experimental data.
The effect of heat treatment on silicon nitride layers on silicon
Authors: Thomas D. J. D.
Published: July 2007

On heat treatment, structural changes may occur in silicon nitride layers deposited on silicon substratres by the glow discharge technique. The causes of the cracks and holes produced in the layer are shown to be thermal stresses and lack of adhesion between the layer and the substrate. Layers produced at above 600 °C, and particularly from silicon tetrachloride, remain perfect on heating up to 1200 °C. Dislocations are introduced into the silicon substrate at defects in the nitride layer. Deformation is produced by slip in the (111) planes parallel to the silicon surface. No defects are introduced into the silicon if the nitride layer remains perfect.
On the Operator of Exciton‐Phonon Interaction
Authors: Davydov A. S.
Published: July 2007

A general expression for the operator for the interaction of molecular excitons with acoustic and optical phonons is obtained in a linear approximation. An explicit expression is found for the dependence of exciton‐phonon interactions on their wave‐vectors for a one dimensional crystal and for crystals of cubic, rhombic and tetragonal systems. The results obtained are compared with the operator for the interaction of free electrons and Wannier excitons with acoustic and optical vibrations in ionic crystals.
Refraktionsmodifizierte Braggsche Beugung bei asymmetrischer Rückstrahl‐Reflexion
Authors: Kunze G.
Published: July 2007

Da das normale Braggsche Gesetz wegen Vernachlässigung der Refraktion vielen festkörperphysikalischen Präzisionserfordernissen nicht mehr gewachsen ist, wurde auf der Basis der kinematischen Theorie der Röntgeninterferenzen für den Allgemeinfall der asymmetrischen Rückstrahl‐Reflexion von ebenen Objekten ein allgemein gültiges Beugungsgesetz aufgestellt. Es gilt uneingeschränkt für Kristalle mit reellen Brechungsindizes und damit auch für lichtoptische Beugungserscheinungen an oder in nicht (oder höchstens schwach) absorbierenden Kristallen mit (quasi‐) superperiodischen Inhomogenitäten (Antiphasenordnungsdomänen, Entmischungszonen, Ausscheidungslamellen, etc.).
Thermally Stimulated Currents without Optical Excitation. Application to Copper Phtalocyanine
Authors: Devaux P. , Schott M.
Published: July 2007

Thermally stimulated current peaks can occur int he absence of previous optical excitation, if at least one of the electrodes on the sample is non‐ohmic. A variety of cases is considered. Most of these cases enable deep‐lying centres which give only very small current peaks to be studied. Their experimental characteristics are presented. They are particularly useful in the case of organic crystals, where optical filling of traps at low temperatures is inefficient and lengthy. This method, applied to copper phtalocyanine, enables centres lying at depths of 0.41 and 0.65 eV, which can not be observed using optical excitation, to be studied.
F‐Center Formation by Fundamental Absorption in KI
Authors: Goldstein F. T.
Published: July 2007

Irradiation of KI in the fundamental edge results in a temperature dependent rate of F‐center growth predominantly proportional to the inverse of the number of F‐centers already produced. This is related to a new experimental result – the quenching of low temperature luminescence in irradiatively colored crystals. In addition, the production of F‐centers by absorption in perturbed exciton bands and the intrinsic production of α‐centers are discussed.
Mössbauer Effect in Iron‐Aluminium Alloys (II)
Authors: Cser L. , Otanevich J. , Pál L.
Published: July 2007

The concentration‐dependence of the isomer shift in iron‐aluminium alloys near the composition Fe3Al is investigated at various temperatures and found to be non‐monotonic. At the temperature of Fe3Al‐type ordering, the isomer shift exhibits a fairly pronounced discontinuity the value of which changes sign with increasing aluminium content. The width of the central line is found to be very broad in the temperature range 550 to 650 °C if the cooling rate is high. This phenomenon can be explained by assuming a transient disordering in the A‐type sublattice which introduces ordering of the D‐type sublattice.
Non‐Ideal Diffusion of Argon in Potassium Chloride
Authors: Schmeling P.
Published: July 2007

The diffusion of Ar39 and Ar41 in single crystals of potassium chloride is studied for the temperature range in which non‐ideal diffusion is predominant. The results are compared with the analysis of obstructed rare‐gas movement by Gaus, and it is shown that all or most of the argon atoms are trapped in crystal defects after irradiation with neutrons. The mechanism for the release of the atoms is sensitive to variations in the irradiation dose and can be related to an activation energy of 2.4 eV only for the lowest doses.
Te and Se Centres in AgBr. I. The g‐, Superhyperfine, and Hyperfine Tensors
Authors: Höhne M. , Stasiw M.
Published: July 2007

Irradiation of AgBr:Te or AgBr:Se with green light at about 180°K produces a paramagnetic centre. It will be shown by investigation of the angular dependence of g‐values, superhyperfine structure, and hyperfine structure that the centre has orthorhombic symmetry, consists of two equivalent impurity anions and strongly interacts with two bromine ions.
Evaluation of the Debye Temperature of Thorium Dioxide
Authors: Ali M. , Nagels P.
Published: July 2007

The Debye temperature of ThO2 is calculated using existing data for heat capacity, neutron diffraction and elastic constants. The resulting values are 259, 268, and 290 °K, respectively. Attention is drawn to the existing confusion in the definition of the Debye temperature which involves the inclusion or exclusion of a factor \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt[3]{3} $\end{document} depending on how the vibrational units are defined.
Unified Theory of Thermionic and Field Emission from Semiconductors
Authors: Christov S. G.
Published: July 2007

The recently developed general theory of electron emission from metals is extended to semiconductors assuming an arbitrary position of the Fermi level at the surface, and a parabolic energy‐momentum relation with an electron effective mass differing from the free electron mass. The expressions obtained for the emission current density from the conduction band are valid for all emission condition between the limits of thermionic and field emission. The formulae for the current originating from the valence band apply to wider emission conditions than those proposed in earlier work.
Higher Order Elastic Constants and the Equation of State of F.C.C. Metals
Authors: Rose M. F.
Published: July 2007

A central potential function is used to calculate the elastic constants through fourth order. It is assumed that the vibrational contribution to the free energy of a solid is given by \documentclass{article}\pagestyle{empty}\begin{document}$ F_{vib} = kT\sum\limits_{i = 1}^{3SN} {\ln 2\sinh \left\{ {\frac{{h\omega _\iota }}{{2\kappa {\rm T}}}} \right\}} $\end{document} and from this, the temperature dependence of the third order elastic constants are calculated. These data are then used to calculate the equation of state of copper, silver, aluminum, and nickel. Agreement between experimental and theoretical equations of state is quite good for pressures as high as 400 kbar.
Stacked Screw Dislocation Arrays in an Anisotropic Two‐Phase Medium
Authors: Chou V. T. , Barnett D. M.
Published: July 2007

The distribution of screw dislocations under an applied stress in uniformly stacked pileups against a second phase is determined. The number of dislocations, n, in each pileup decreases as the separation h between pileups decreases and as the ratio of the shear moduli of the second and the matrix phases (G″/G′ in the isotropic case) increases. The stress field produced in the second phase is quantitatively described. For L/η′ ≫ x/η″, the intensity of the stress field at a distance x from the tip of each pileup varies as \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\tanh \frac{{\pi L}}{{\eta \prime h}}/\tanh \frac{{\pi x}}{{\eta \prime \prime h}}}\right)^\lambda $\end{document} where L is the length of the pileup, η′ and η″ are respectively functions of the elastic constants of the matrix and the second phases, and λ is a monotone decreasing function of the ratio of the shear moduli, varying in the range 1 > λ > 0 as the ratio varies between 0 and ∞. The stress concentration near the tip thus decreases as h decreases and as the modulus ratio increases. A number of special cases derived from the general solution are discussed.
Die Richtungsverteilung der Frequenzen von Gitterschwingungen einer festen Wellenzahl
Authors: Mika K.
Published: July 2007

Zur Berechnung der Richtungsverteilung gq(ω) von akustischen Schwingungsfrequenzen vorgegebener Wellenzahl q werden die „kritischen Punkte”︁ von Dispersionsflächen ωs(θ φ)gesucht. Am Beispiel der kubisch primitiven Gitter werden diese Flächen in der Umgebung der Symmetrierichtungen diskutiert, im linearen Dispersionsbereich werden hierdurch gleichzeitig sämtliche kritischen Punkte festgelegt. Das sich hieraus ergebende Spektrum gq(ω) zeigt Merkmale wie das von van Hove untersuchte Gesamtspektrum eines zwei‐dimensionalen Kristalls.
On the Magnetocrystalline Anisotropy of NiCo Ferrites
Authors: Elbinger G.
Published: July 2007

The magnetocrystalline anisotropy of CoxNi1−xFe2O4 ± γ is measured at room temperature by torque measurements. It is found that an additional couple caused by the anisodropy of the magnetization must be taken into account in the determination of the magnetocrystalline constants. For the (100)‐plane is found that the magnetocrystalline anisotropy increases nearly linearly with the Co‐content. The constants k1 of the anisotropy of the magnetization also increase linearly at low Co‐additions, but at higher Co‐concentrations the increase is less than linear. Measurements in the (111)‐plane show a marked dependence of Lmax on the magnetic field strength. Attempts to find the values of the constants by extrapolation prove unsuccesful.
A Source of Dislocations in Copper Crystals
Authors: Clarebrough L. M. , Michell D. , Smith A. P.
Published: July 2007

In single crystals of copper annealed in hydrogen, dislocations are generated by prismatic punching during cooling at 3 °C/s. The centres of punching are voids formed by vacancy clustering and the stress necessary to generate dislocations arises from an internal pressure of hydrogen in the voids.
Thermally Stimulated Currents under the Condition of Persistent Internal Polarization
Authors: Zolotaryov V. F. , Semak D. G. , Chepur D. V.
Published: July 2007

A new method is proposed for direct determination of the trapping levels which are responsible for internal polarization in semiconductors. The method is based on the fact that internal polarization, i. e. the internal field, becomes important at low temperatures. In the presence of the internal field, the trapping levels are then investigated by the thermally‐stimulated‐current method. The internal field affects the temperature dependence of the thermally stimulated current. The thermally stimulated current shows a quadratic dependence on carrier concentration in the conduction band. This is the reason for the contraction of the thermally stimulated current maxima and the improvement in their separation.
Selection Rules for Two‐Phonon Absorption Processes
Authors: Hulin M.
Published: July 2007

A model for the interaction between photons and phonons which includes the crystal electrons is proposed in order to investigate the possible selection rules for absorption processes involving the emission of two phonons. The main results can be rederived; special attention is given to the problem of harmonics especially in crystals possessing inversion symmetry.
Electrical Resistivity in Antiferromagnetic Alloys
Authors: Masharov S. I.
Published: July 2007

A generalization of the s‐d–exchange model developed for domains in binary antiferromagnetic alloys is presented. It is shown that departures from the the ideal periodicity in the distribution of atoms among the lattice sites leads to a number of interaction processes between elementary excitations in the electron and spin sub‐systems which do not occur in ideal antiferromagnetics. In particular, electron‐magnon collisions arise which do not conserve quasi‐momentum. In the low temperature range these effects are dominant in the scattering of conduction electrons, giving rise, to a term proportional to T2 in the electrical resistivity.
Theory of Resonant Secondary Radiation due to Impurity Centres in Crystals
Authors: Hizhyakov V. , Tehver I.
Published: July 2007

The resonant secondary radiation spectrum of impurity centres in crystals is studied on the basis of a second‐order approximation for the interaction between the electromagnetic field and the material. It is shown that for the case of excitation in the phonon wing of the absorption band, the main part of the secondary radiation represents the ordinary luminescence. The spectrum also contains Rayleigh and Raman scattering which is considerably weaker (by about four orders of magnitude). Formulas are obtained for the intensities of Rayleigh‐ and Raman scattering; particular consideration is made for the case of large Stokes' losses. It is also shown that excitation in the region of the pure‐electronic line yields a spectrum consisting of the Rayleigh and the pure‐electronic line, and the phonon wing of the luminescence.
Generation–Recombination and Diffusion Noise in Cadmium Sulphide Photoconductors
Authors: Damodar‐Pai M. , van Vliet K. M.
Published: July 2007

Noise in CdS stemming from generation–recombination, trapping, diffusion, and drift is investigated. In the treatment, the transport equations corresponding to a four‐level model are considered. Closed form expressions for the various parts of the spectrum and for the pertinent relaxation times are given. Experimental results demonstrated many features of the computed spectra, particularly for absorption in the long‐wavelength tail. Some quantitative values for the rate constants and effective diffusion constants are derived. The relative variance of the spectra, <ΔN2>/N0 is found to be close to unity.
Zur Auswertung isochroner Ausheilkurven
Authors: Balarin M. , Rattke R. , Zetzsche A.
Published: July 2007

Es wird gezeigt, welche Unterschiede zu beachten sind, wenn die für zeitlineare Erholungskurven bekannten Auswertungsmethoden zur quantitativen Bestimmung der Aktivierungsenergie auf isochrone Erholungskurven übertragen werden sollen. Es werden behandelt: die Auswertung des Verlaufs einer einzelnen Erholungskurve und die Auswertung der Temperaturverschiebung infolge unterschiedlicher Aufheizgeschwindigkeiten.
The Use of the Magneto‐Optical Kerr Effect for the Determination of Magnetization Curves
Authors: Stoll M.‐P.
Published: July 2007

Magnetization curves obtained by means of magnetooptical Kerr rotation show important differences from the usual curves. This phenomenon is assumed to be related to the spatial distribution of the local directions of magnetization. In the case of polycrystalline samples, the rotation may be calculated for weak applied fields, and this is in good agreement with the experimental curves. The results indicate that a surface pinning effect is likely to occur. For single‐crystal mirrors, the magneto‐optical curves are, in special cases, similar to the usual magnetization curves in the high field region.
An Analysis of the Cottrell‐Stokes Law
Authors: Evans K. R. , Flanagan W. F.
Published: July 2007

The retarding force profiles available for copper and its solid‐solutions are shown to explain reported deviations from the Cottrell‐Stokes law. It is shown that the Cottrell‐Stokes law is not valid and only approximated when a large athermal force must be overcome by an applied stress attempting to translate a dislocation segment past a rate‐controlling obstacle to dislocation motion.
On the Theory of Electrical Domains in Hot Electron Semiconductors
Authors: Bonch‐Bruevich V. L.
Published: July 2007

An analysis is given of the conditions under which exist stationary moving domains in hot electron semiconductors. The criteria for soft and hard regimes of domain excitation are obtained. It is shown that several domain modes may exist which propagate with different velocities. The problem of the current oscillations in the external circuit is considered briefly and the conditions under which such oscillations appeare are stated.
The Second Ferroelectric Phase Transition in NaH3(SeO3)2 Crystals and their Physical Properties
Authors: Shuvalov L. A. , Ivanov N. R.
Published: July 2007

An investigation is made of the spontaneous polarisation, the coercive field, the dielectric constant, the electro‐optical behaviour, and the domain structure of ferroelectric NaH3(SeO3)2 single crystals in the temperature range −195 to 0 °C. The existence of two phase transitions and two ferroelectric phases is confirmed; the presence of two domain systems and a contribution of this domains to the dielectric constant in the triclinic ferroelectric phase is observed. The multiaxial electrical behaviour of the crystals in this phase, the enantiomorphism of the domains, and other peculiarities of electrical twinning are discussed. A large difference is noted in the behaviour of the mutually orthogonal components of the spontaneous polarization.
Contribution of Thermal Vibrations to the Anomalous Transmission of X‐Rays
Authors: Efimov O. N.
Published: July 2007

The contribution of the thermal vibrations to the real and imaginary parts of the structure factor is discussed on the basis of experimental temperature dependences of integral characteristics for the anomalous transmission of X‐rays in germanium between 85 and 650 °K. The deviation of the temperature dependence of the imaginary part of the structure factor from the form Fihe−M (M Debye‐Waller factor) is in good agreement with a theoretical analysis. This analysis takes into account the contributions from phonon scattering on phonons by considering a dynamic solution of the problem.
On the Theory of Spontaneous Hall Effect at Low Temperatures
Authors: Irkhin Yu. P. , Voloshinskii A. N. , Abelskii Sh. Sh.
Published: July 2007

A study is made of the spontaneous Hall effect in ferromagnetic metals caused by the anisotropy of the scattering of conduction electrons by spin waves. The temperature dependence of the spontaneous Hall coefficient is given by Rs = α T3 + β T4, where the first term is due to the interaction of the conduction electron orbits with the spins of the magnetic electrons and the second term is due to the spin‐orbit interaction between the magnetic electrons themselves.
Phase Diagram of the Alloy System HgTeCdTe
Authors: Ray B. , Spencer P. M.
Published: July 2007

The solidus and liquidus for the pseudo‐binary alloy system HgTeCdTe has been determined with differential thermal analysis and X‐ray techniques. Solid solution exists throughout the system. The liquidus deviates slightly from the linear but the solidus rises very slowly with increasing CdTe concentration to approximately 40 mol%. At higher concentrations the increase is more rapid.
The Effect of the Type of Splitting of Screw Dislocations on the Slip Geometry in B.C.C. Metals
Authors: Vítek V.
Published: July 2007

A theory of slip geometry in b.c.c. metals is given which is based on the assumption that the sessile‐glissile transformations of the splitting of screw dislocations are continually repeated during their motion. The sessile splitting is assumed to occur via the reaction 1/2 [111] = 1/6 [111] + 1/6 [111] + 1/6 [111] on a {110} and a {112} plane simultaneously as proposed by Foxall, Duesbery, and Hirsch [14]. The theory is developed analogically as in [8] where a different type of splitting was used. The previous results are compared with the present results for Fe‐3% Si and niobium.
The Influence of Carbon on Precipitation of Copper in Silicon Single Crystals
Authors: Fiermans L. , Vennik J.
Published: July 2007

The effect of carbon on the copper precipitation behaviour of dislocation‐free silicon crystals with low oxygen concentration, is studied by infra‐red microscopy, high‐resolution X‐ray topography and infra‐red spectrophotometry. A growth mechanism is proposed for the copper precipitates which is based on indentation at silicon carbide or silica precipitates, followed by climb of dislocation loops. The main type of dislocation likely to produce the observed pattern, is thought to be the 〈100〉 edge dislocations.
Dielectric and Optical Absorption Measurements on CaF2 and CaF2:Y
Authors: Caffyn J. E. , Goodfellow T. L. , Olymbios E. M. , Perrin D. J.
Published: July 2007

Crystals of oxygen free and oxygen contaminated CaF2 were doped with yttrium. The dielectric loss of the unirradiated crystals was measured at 150 °C at different frequencies and a shift of the peak in the curves was found with varying concentration of yttrium. In oxygen free crystals the peak was displaced to higher frequencies whilst with oxygen contaminated crystals the shift was to lower frequencies. The optical absorption spectra were taken at room temperature before and after room temperature X‐irradiation. The uv optical absorption that exists in oxygen contaminated crystals even before X‐irradiation was found to decrease in yttrium doped crystals grown from oxygen contaminated material. It is proposed that the observed results could be explained on the assumption that one or more of the following associated defects are present in the crystals, namely: 1. an oxygen ion and fluorine ion vacancy, 2. an yttrium ion and an interstitial fluorine ion, 3. an yttrium ion and a substitutional oxygen ion. The shift of the dielectric loss peak to lower frequencies for yttrium doped oxygen contaminated crystals is correlated with the reduction of the uv optical absorption. It is suggested that possible explanation for this reduction is due to the formation of yttrium—oxygen dipoles. Thermal annealing of these crystals provides further confirmation of this suggestion.
Potential of a Vacant Site in the Graphite Lattice
Authors: Bogdanović R.
Published: July 2007

A discussion is given of the various methods available for computing the potential of a vacant site in the graphite lattice. The Hartree‐Fock‐Slater potential is computed here according to the Hartree‐Fock functions for the free carbon ion.
On the Nature of the Long‐Range Dislocation Contrast in Electron Transmission Micrographs
Authors: Wilkens M. , Rühle M. , Hässermann F.
Published: July 2007

The background contrast of dislocations is investigated theoretically using modified Bloch waves. As a result it is found that interband scattering can be neglected outside the dark line (width ≦ one extinction distance) of the dislocation image. The contrast outside the dark line is quantitatively explained by “phase contrast” [4]. i.e. exclusively by the movement of the excitation points of the modified Bloch waves on the dispersion branches. It is shown that the asymmetry often observed in the background intensities adjacent to the black line is an intrinsic contrast phenomenon rather than a consequence of stress relaxation at the foil surface.