bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Field Emission of Minority Carriers in Photoconductors
Authors: Döhler G. 
Published: July 2007

AbstractLayer‐like field inhomogeneities in homogeneous photoconductors are discussed using the model proposed by Kiess and Stöckmann, referring to the field emission of minority carriers. By neglecting diffusion, the stationary solutions obtained are shown to describe the potential variations measured in CdS by Kiess indicating a new current saturation effect in photoconductors. Some experimental results on current oscillations observed in Se by Polke and Hasler are also discussed.
Recombination in Semiconductors by a Light Hole Auger Transition
Authors: Beattie A. R. , Smith G. 
Published: July 2007

AbstractThe transition rates for an Auger collision process in semiconductors which involves the light hole band is calculated using a quantum mechanical perturbation method. Spherical energy surfaces are assumed although non parabolic energy bands are allowed for. The temperature dependence of the lifetime of excess carriers due to this process is investigated and the results applied to InSb and InAs in the temperature range 200 to 500°K. The shape of the temperature dependence of this theoretical lifetime for InSb agrees well with experiment at room temperature and above, and when estimates of overlap parameters which occur in the theory are made the absolute magnitude of the lifetime also agrees with experiment. The probability per unit time that a light hole created by a photon of energy h v will take part in an impact ionizing transition is also given as a function of h v. It is concluded that the transition rate for this process is at least comparable to that of the more usual Auger transitions involving the heavy hole and conduction bands only.
Verteilungsfunktion und Driftgeschwindigkeit warmer Elektronen in Germanium
Authors: Franz W. , Miosga P. 
Published: July 2007

AbstractDas in [1] und [2] beschriebene Verfahren, nach welchem die Verteilungsfunktion heißer Elektronen durch iterative Quadraturen bestimmt wurde, wird für den Fall kleiner elektrischer Felder modifiziert. Die Ergebnisse einer Rechnung für Germanium zeigen bei höheren Temperaturen befriedigende Übereinstimmung mit Messungen.
Influence of Ordering on the Properties of Solid Solutions of the System (HgSe)3x‐(In2Se3)1−x
Authors: Gavrilitsa E. I. , Radautsan S. I. 
Published: July 2007

AbstractSome results are given of an investigation of the transition effect in solid solutions of the system (HgSe)3x‐(In2Se3)1−x. The concentration and thermal ordering of the atomic components and defects in the cation sublattice are found to have an important effect on the electron mobility and lattice thermal conductivity.
Elastische Konstanten des Flußfadengitters in Supraleitern zweiter Art
Authors: Labusch R. 
Published: July 2007

AbstractDie elastischen Konstanten des Flußfadengitters in Supraleitern zweiter Art werden erneut aus dem Wechselwirkungspotential zwischen den Flußlinien berechnet. Hierbei werden Irrtümer früherer Autoren vermieden. Unter der vernünftigen Annahme von Dreieckssymmetrie lassen sich alle Konstanten durch die Parameter der gemessenen reversiblen Magnetisierungskurve ausdrücken. Als Beispiel werden die berechneten elastischen Konstanten des Flußfadengitters in Niob bei 4,15°K als Funktion des angelegten Magnetfeldes aufgetragen.
Streuung langsamer Neutronen an polykristallinem Selen und Tellur
Authors: Axmann A. , Gissler W. 
Published: July 2007

AbstractMit Hilfe eines Drehkristall‐Flugzeitspektrometers wurde die inelastische Streuung langsamer Neutronen an polykristallinem Selen und Tellur untersucht. Es wurden verschiedene Bandenschwerpunkte gefunden, die in ihrer Lage gut mit den durch Infrarotmessungen [1] ermittelten übereinstimmen, jedoch ist ihre Anzahl kleiner. Dieser Umstand zeigt, daß die neutronenspektroskopisch nicht beobachteten Übergänge von Kombinationen herrühren. Bezüglich des Tellurspektrums ergibt sich eine gute Übereinstimmung mit der Theorie von Hulin [4]. Die Neutronenspektren der beiden isomorphen Kristalle sind einander ähnlich.
Zur Theorie der Erzeugung der zweiten Harmonischen an der Oberfläche eines unmagnetischen, quadratischen, optisch einachsigen Kristalls
Authors: Fischer R. 
Published: July 2007

AbstractFällt eine intensive monochromatische, elektromagnetische Welle auf die Grenzfläche eines optisch nichtlinearen Kristalls, so erfolgt eine Wechselwirkung, die zur Erzeugung einer zweiten Harmonischen führen kann. Neben der sich im nichtlinearen Medium ausbreitenden zweiten Harmonischen tritt auch eine reflektierte Harmonische auf. Es werden Verallgemeinerungen des Reflexions‐ und Brechungsgesetzes und der Fresnelschen Formeln für den Fall abgeleitet, daß eine ebene Grundwelle aus einem unmagnetischen, nichtabsorbierenden, isotropen, linearen Medium auf die ebene Grenzfläche eines unmagnetischen, optisch einachsigen, optisch nichtlinearen (quadratischen) Kristalls fällt. Das Problem wird in parametrischer Näherung gelöst. Es wird vorausgesetzt, daß sich die Polarisationswellen nicht in einer Synchronisationsrichtung ausbreiten.
Oscillations collectives de spins et ordre à courte distance
Authors: Villain J. 
Published: July 2007

AbstractNous étudions les oscillations collectives de spins à partir des deux premières dérivées non nulles de la fonction de corrélation (Sk(t), S−k) pour t = 0, pour le calcul desquelles nous développons une approximation appropriée. Aux températures inférieures au point de transition on trouve pour la fréquence une formule identique à celle obtenue dans l'approximation des ondes de spin, mais l'approximation est en défaut pour k petit. Il semble que, dans les réseaux tridimensionnels isotropes, les oscillations de spins aient complètement disparu au point de transition. Par contre elles peuvent exister en l'absence d'ordre à grande distance si l'ordre à courte distance est intense, notamment dans un réseau plan ou linéaire.
The Condition for Negative Absorption in Semiconductors
Authors: Landsberg P. T. 
Published: July 2007

AbstractFor a given photon energy h v the condition that the stimulated emission rate exceeds the absorption rate is Fc ‐ Fv > h v when the F's are quasi‐Fermi levels for conduction and valence bands. This holds also if phonons are involved. The condition is generalised here to the case where several electrons and phonons are involved and localised or band states play a part. The condition becomes: The drop in the quasi‐Gibbs free energy of the electron system as a result of one radiative transition must exceed h v.
Interference Effects in Spin Lattice Relaxation by Two‐Phonon Processes
Authors: Stoneham A. M. 
Published: July 2007

AbstractThe usual theory of relaxation by two‐phonon processes assumes that the relaxation rate is the sum of a non‐resonant Raman contribution and resonant Orbach contributions. This neglects terms which may be regarded as interference between these contributions and which appear when several excited states contribute to the relaxation. These terms affect the temperature dependence of the relaxation rate and will affect the values of energy level splittings obtained from the Orbach terms. Further the contributions of the several excited states to the relaxation rate may themselves tend to cancel. The usual approximation of omitting phonon energies in energy denominators is then invalid, as the cancellation is sensitive to their presence. A comparison of the exact theory and the usual theory is made for MgO:Co2+. Agreement with experiment is rather better in the exact treatment, but poor in both cases. Possible reasons for the discrepancy are suggested.
The Yield Point of α‐Copper–Tin Alloys
Authors: Vöhringer O. , Macherauch E. 
Published: July 2007

AbstractDynamics tensile tests (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document} = 1.6 × 10−4 s−1) are performed on polycrystalline α‐Cu‐Sn alloys. The effects of temperature (T) and composition (c) on the yield point σSt are investigated. In the temperature range T ⪅ 300°K the relation σSt = (a1 ‐ b1 T1/3) \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt c $\end{document} holds where a1 and b1 are constants. This dependence can be estimated theoretically from the elastic interaction of Sn‐atoms with dislocations. Theory and experiment agree quite well.
Orientation Dependence of the Ferroelectricity of T.G.S.
Authors: Jiménez B. , Mendiola J. , Maurer E. 
Published: July 2007

AbstractThe ferroelectric behaviour of T.G.S. single crystals is studied for slabs cut along directions which form gradual orientations with the polar axis [010]. Distinct ferroelectric phenomena are observed for several directions, even for orientations well away from the polar axis, where perfectly defined ferroelectric properties are obtained (hysteresis loop, λ‐curve of the dielectric constant, and maximum switching current). The results are interpreted on the basis of a simple consideration of H‐bond contributions to the ferroelectricity. The theoretical conclusions are in good agreement with the experimental results.
Leitfähigkeit und Feldeffekt reiner Siliziumspaltflächen
Authors: Henzler M. 
Published: July 2007

AbstractAn Siliziumkristallen (etwa 104 ωcm, p‐leitend), die im Ultrahochvakuum gespalten worden waren, wurden Oberflächenleitfähigkeit und Feldeffekt gemessen. Durch eine Abschirmung der Proben und Messung des Feldeffektes für verschiedene Abstände der Feldelektrode konnte der verfälschende Beitrag der oxidbedeckten Seitenflächen ausgeschaltet werden. Die reine Oberfläche ergibt sich als schwach p‐leitend (Δσ = (4,2 ± 1,3) × 10−7 A/V) mit einer hohen Dichte von Oberflächenzuständen (SE = 1014 eV−1 cm−2). Durch Wasserdampf wird die Spaltfläche stark n‐leitend, während durch Sauerstoff die Oberflächenleitfähigkeit nahezu den Minimalwert zwischen p‐ und n‐Leitung annimmt.
Electron Charge Distribution about Zinc Ions in Aluminum
Authors: van Torne L. I. 
Published: July 2007

AbstractThe electron charge density distribution about a zinc solute ion in a dilute aluminum alloy is computed by three different methods. These are: a) an exact method where the solute ion potential is derived from the model potential difference between zinc and aluminum, b) a semiempirical method where the partial wave phase shifts are obtained from alloy specific electrical resistivity, and c) an approximate method where the solute ion potential is represented by a screened Coulomb potential. All three methods are in agreement with the experimentally observed solute ion clustering. Methods a and b also are in agreement with the observed decrease in lattice parameter with increase in zinc content.
Plastische Verformung von Eisen‐II‐Oxid
Authors: Reppich B. 
Published: July 2007

AbstractEinkristallines und polykristallines Eisen‐II‐Oxid, Fei1–xO, mit einem Kationenleerstellengehalt von 0, 05 ≦ x ≦ 0, 11 wurde im Stauchversuch bei Temperaturen 650 °C ≦ T ≦ 1300 °C statisch und dynamisch verformt. Stationäres Kriechen und dynamisches Fließen lassen sich beschreiben durch die Zustandsgleichung ε˙ = C (1 + bx) σm exp( –U/kT) mit m = 4 und U = (3.54 ± 0,21) eV ⌆ (81, 5 ± 4.8) kcal/mol. Einkristalle sind weicher und duktiler als Polykristalle. Fe1–xO wird mit steigendem Leerstellengehalt x plastischer. Für die beobachtete Streckgrenze werden die von Fe3O4‐Ausscheidungen herrührenden Versetzungsringe verantwortlich gemacht. Die Ergebnisse lassen sich durch ein von der Spannung unterstütztes Klettern von Stufenversetzungen deuten.
On the Theory of Thermally Activated Processes
Authors: Geszti T. 
Published: July 2007

AbstractThe range of validity of “rate theory” is investigated and a clear distinction is made between “directional” and complete thermalization. It is suggested that the first process determines the hopping character of the motion, while the second determines whether the usual quasi‐equilibrium description is applicable. Macroscopic diffusion is shown always to obey “rate theory”, while frequency‐dependent dielectric or anelastic loss may shown non‐equilibrium effects. In the case in which complete thermalization is slow (although directional thermalization may be fast) a succession of Lorentzian peaks is obtained instead of the single peak predicted by rate theory. Qualitative dynamic conditions are presented for slow thermalization behaviour.
The Determination of the Orientation of Micro‐Crystals Using a Back‐Reflection Kossel Technique and an Electron Probe Microanalyser
Authors: Bevis M. , Swindells N. 
Published: July 2007

AbstractThe determination of the orientation of small single crystals from back‐reflection Kossel patterns obtained by using an electron probe microanalyser is considered. A procedure for determining the indices of directions in the crystal represented by the intersection of Kossel lines is presented, and the way in which this information may be used for determining the orientation of crystals without the aid of the stereographic projection is described. Complementary procedures for determining the full orientation of small crystals and the orientation of interface planes in these crystals are also described. To illustrate these procedures the orientation relationship between annealing twins and the matrix in an f.c.c. crystal has been determined together with the orientation of the twin matrix interface planes.
Surface and Volume Diffusion in Thin Films of the System AgSe
Authors: Pines B. Ya. , Grebennik I. P. , Bazyura R. I. , Zozulya G. V. 
Published: July 2007

AbstractThe course of volume and surface diffusion in thin (10−5 to 10−6 cm) films of the system AgSe was investigated by means of electron diffraction and microscopic studies. The surface diffusion determines the growing speed of the two component region in specimens that have partly superimposed layers of components. Volume diffusion equalizes the concentration in the thickness direction of the film. The kinetics of the surface diffusion of Ag over Se could be stated by observing the displacement of the crystallisation front of amorphous selenium. The surface diffusion of Se over Ag was controlled by the appearing α‐Ag2Se diffraction lines near the edge of the two component region.
ESR Studies of Cu2+ in NH4Cl Single Crystals between 4.2 and 453 °K. I. Spin‐Hamiltonian Parameters and Lattice Constant for NH4Cl
Authors: Pilbrow J. R. , Spaeth J. M. 
Published: July 2007

AbstractESR spectra from two different Cu2+ with [100] tetragonal symmetry were observed in NH4Cl single crystals. The spin‐Hamiltonian parameters for both centres were determined in the temperature range 4.2 to 453 °K where NH4Cl has the CsCl structure. The g‐values and hyperfine constants for both centres show a marked anomaly in the vicinity of the λ‐point and significant variations over the whole temperature range. Both centres have essentially a |3 z2 – r2〉 ground state, but with evidence of vibrational admixtures of the |x2 – y2〉 state. In view of possible future calculations of the Cu2+ spin polarization and radial wave function for the ground state, the lattice parameter of NH4Cl and NH4Cl:Cu was measured in the temperature range 105 to 453 °K.
ESR Studies of Cu2+ in NH4Cl Single Crystals between 4.2 and 453 °K. II. Theoretical Analysis: Vibrational Admixtures, Spin Polarization, and 〈r−3〉 for Cu2+ Ions
Authors: Pilbrow J. R. , Spaeth J. M. 
Published: July 2007

AbstractThe temperature dependence of the spin‐Hamiltonian parameters for two Cu2+ centres in NH4Cl single crystals, which were reported in the previous paper (I), is analysed in detail. The results show that, apart from zero point vibrations, higher lattice modes also contribute to the admixture of the |x2 – y2〉 state into the |3 z2 – r2〉 ground state for these centres. For one of the centres there is also evidence that vibrations and reorientations of a single nearest neighbour NH4+ ion contribute to the admixture. From the analysis, the temperature dependence of 〈r−3〉3z2 – r2, a crystal field splitting parameter and the contact contribution to the hyperfine field at the Cu2+ nucleus is obtained. All these quantities vary strongly with temperature and show sudden changes at the λ‐point ( −30.5 °C) for NH4Cl. The temperature dependence of the contact term in the hyperfine interaction can be qualitatively understood in terms of core spin polarization by taking into account the observed changes in the radial distribution of the 3d ground state. The analysis gives further support for the models proposed for the two Cu2+ centres.
On the Theory of Electrical Resistivity of Polyvalent Metals
Authors: Bross H. , Bohn G. 
Published: July 2007

AbstractIn the case of polyvalent metals, the singularities in the transition probability determined by Bardeen can be avoided by performing the integration over the atomic polyhedron instead of the Wigner‐Seitz‐sphere. This new expression for the transition probability is used to compute the temperature‐dependence of the electrical resistivity for aluminium. Anisotropic effects due to the lattice waves are taken into account by a variational procedure. The agreement with experimental results is satisfactory.
Lattice Specific Heats of Thallium and Yttrium
Authors: Gupta R. P. 
Published: July 2007

AbstractThe lattice specific heats of thallium and yttrium are calculated using the electron gas model of Gupta and Dayal for hexagonal metals. The interactions are restricted to fourth neighbours. The force constants are determined from experimental values of the elastic constants. The θ‐T curves calculated from the computed specific heats show a fairly satisfactory agreement with the experimental values, i.e. the difference is not greater than 3% for thallium and 6% for yttrium.
The Influence of Collisions on the Franz‐Keldysh Effect
Authors: Enderlein R. 
Published: July 2007

AbstractA study is made of the effect fo electron‐phonon and electron‐impurity scattering on the field‐induced change in the optical interband absorption for photon energies near the direct band gap ℏ ω0. It is found that in the presence of collisions the exponential tail of the absorption coefficient at ω < ω0 oscillates and that the oscillations at ω > ω0 are damped. This damping seems to be in quantitative agreement with the experimental results of Hamakawa, Germano and Handler [4].
Role of Carrier Polarization in the Mechanism of the Electroluminescence of ZnSMn Films
Authors: Vlasenko N. A. , Zynio S. A. 
Published: July 2007

AbstractA polarization which remains constant over a period of time and is caused by the accumulation of carriers in deep surface traps is observed in EL ZnSMn films. The polarization characteristics (i.e., the number of polarization charges, the time‐dependence of its formation and destruction, the ionization energy of the traps, etc.) are determined in order to study the role of carrier polarization in the mechanism of EL. It is established that the polarization mainly affects the change in the internal field and therefore the impact ionization probability. Also, at the instant of voltage‐polarity reversal, the polarization charge ionization leads to an increase in the number of carriers which can accelerate. All the EL properties and features of ZnSMn films may be explained on the basis of an impactionization mechanism if the polarization effects are taken into account.
Electron Spin Resonance of Tl++ Centres in KCl Crystals
Authors: Dreybrodt W. , Silber D. 
Published: July 2007

AbstractThallium‐doped KCl crystals are X‐rayed at 77 °K. They are warmed up to 300 °K and then cooled down again to 77 °K. ESR signals showing a resolved hyperfine structure due to six chlorines are observed. These arise from a Tl++ ion on a cation lattice site. The constants of the spin‐Hamiltonian are determined. Using Watanabe's theory [1] the coefficients of the ground state LCAO function are determined from the h.f.s. constants. From these data and from data of the optical absorption spectrum of Tl++ [3] the g‐shift is calculated and compared with the experimental value.
A Model for the Lattice Dynamics of Naphthalene and Anthracene
Authors: Pawley G. S. 
Published: July 2007

AbstractThe lattice dynamics of a model for naphthalene and anthracene is presented. Intermolecular forces of the ‘6‐exp’ interatomic type are assumed, and dispersion curves are calculated. It is stressed that the Raman modes do not involve rotations about the principal inertia axes. Frequency distributions, Debye temperatures and Debye‐Waller factors are calculated, and the validity of using the last to estimate Raman frequencies is assessed. The agreement with experiment is good, except perhaps, for the elastic constants. Finally the thermal diffuse X‐ray scattering is calculated and compared with experiment. The low resolution results agree both with experiment and with the ‘difference Fourier transform’ theory. The high resolution calculation, however, explains the discrepancies between experiment and the earlier theory.
Effect of Concentration on Light Absorption and Dispersion by Impurity Centres in the Case of Weak Electron–Phonon Coupling (II)
Authors: Lubchenko A. F. , Dudkin S. I. 
Published: July 2007

AbstractThe two‐particle Green's function method is used to investigate the dependence of light absorption and dispersion due to substitutional impurity centres upon their concentration in the case of weak electron‐phonon coupling, taking into account the change of the quasi‐elastic constants due to the substitution. At low impurity concentrations the half‐width of the zero‐phonon line and the corresponding dispersion curve as well as their position in the spectrum are shown to vary linearly with concentration; at higher concentration the absorption coefficient may deviate from linearity.
Magnetic Ordering in Uranium Compounds with Crystal Structures of Anti‐Cu2Sb and PbFCl Types. Molecular Field Approximation
Authors: Przystawa J. , Suski W. 
Published: July 2007

AbstractThe eight possible types of collinear magnetic structure are determined in the molecular field approximation with the help of Smart's and Bertaut's methods. The Heisenberg isotropic model with five nearest‐neighbour exchange integrals is used. The stability conditions are presented in terms of phase diagrams.
Tilt Boundaries in Deformed Anthracene Single Crystals
Authors: Robinson P. M. , Scott H. G. 
Published: July 2007

AbstractAnthracene single crystals have been deformed by cleaving and by bending. In both cases, immobile tilt boundaries approximately perpendicular to the basal planes were observed. These boundaries were slightly asymmetric with respect to the basal planes on either side. It is believed that the boundaries consist mainly of mobile dislocations with Burgers vectors in the basal plane. The asymmetry of the boundaries is thought to be due to the incorporation of a few dislocations whose Burgers vectors lie in the other planes; these dislocations also serve to pin the boundary.
On the Electric and Thermoelectric Properties of Copper Phthalocyanine Single Crystals
Authors: Hamann C. 
Published: July 2007

AbstractComparative measurements are made on single crystals of copper phthalocyanine in order to investigate the electric, thermoelectric, and galvanomagnetic properties. A simple model is used to explain the thermoelectric measurements and the space‐charge limited current characteristics. This involves presence of electron traps of concentration of the order of 1013 to 1014 cm−3 and trap depth 0.88 eV below the conduction band. Copper phthalocyanine is an intrinsic semiconductor having an activation energy of 2.0 eV.
Effect of Pressure on the Diffusion of Fe in Ti and Ti + 10% Fe
Authors: Peart R. F. 
Published: July 2007

AbstractMeasurements have been made of the variation of the diffusion coefficient of Fe as a function of hydrostatic pressure in Ti at 902 °C and of Fe in Ti + 10% Fe at 808 °C. Hydrostatic pressures up to 4000 atm were used. For Ti + 10% Fe the diffusion coefficient decreases with pressure and corresponds to a value of 0.6 for the ratio of the activation volume to the atomic volume. For Ti the diffusion coefficient increases nonlinearly with pressure. These results are discussed in terms of diffusion due to vacancies, interstitials, and sub‐grain boundary networks.