bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Step Annealing Procedure for the Determination of Diffusion Coefficients in Metals by the Resistometric Method‐Application to the Diffusion of Cu in Al
Authors: Ceresara S. 
Published: July 2007

AbstractA simple experimental procedure is described which enables the resistometric determination of diffusion coefficients in metals by the employment of only one diffusion sample. Results obtained for diffusion of Cu in Al well compare with data reported in the literature.
On the Theory of Shallow Impurity States
Authors: Sak J. 
Published: July 2007

AbstractA theoretical investigation is made of the shallow states of an impurity interacting weakly with polar phonons. An effective mass equation is found containing besides usual terms corrections including the renormalization of the electron mass, deviations from the parabolic dispersion law (due to phonons), and a contact term arising from the interaction of the electron with the fluctuations of the phonon field. Physical interpretation of the contact interaction is given. Analogy between a polaron and an electronic polaron is recalled to draw some conclusions concerning electron‐electron correlation. The shift of the lowest energy level of a hydrogen‐like impurity is calculated.
Twist Boundaries and Electroluminescence
Authors: Daniels B. K. , Meadowcroft D. B. 
Published: July 2007

AbstractTwist boundaries have been introduced into needle crystals of zinc sulphide and their effects on electroluminescence investigated. Because of the very small size of the crystals a special experimental technique was developed. Within the limit of accuracy of the experimental measurements no effects of the twist boundaries could be detected. This result is examined from several points of view and further possible experiments are suggested.
The Influence of Structure on the Electroluminescence of Zinc Sulphide
Authors: Alfrey G. F. , Meadowcroft D. B. 
Published: July 2007

AbstractElectroluminescence has been measured from small regions within vapour‐grown ZnS crystals, and can be correlated with the crystal structure of the regions, since impurity content and other factors should be constant in these conditions. The emission is found to be lower for disordered structures, in contrast to previous work on phosphors. It is suggested that, at the low activator concentrations prevailing, decoration of dislocations does not occur, so that processes depending on conducting inclusions are inoperative. Scattering at the defects will, on the other hand, reduce the efficiency of impact excitation.
Electrical and Optical Properties of Sputtered In2O3 films. I. Electrical Properties and Intrinsic Absorption
Authors: Müller H. K. 
Published: July 2007

AbstractThin films of n‐conducting In2O3 are prepared by reactive sputtering. The concentration of conduction electrons is changed by a heat treatment between ne = 1017 and 1020 cm−3 (T = 300°K). Concentration and temperature dependence of the electron mobility indicate an intense scattering at charged imperfection centres which are due to a considerable intrinsic lattice disorder. The intrinsic absorption is also influenced by this disorder.
Thermoelectric Force of hot Carriers
Authors: Pozhela J. K. , Repshas K. K. 
Published: July 2007

AbstractThe thermo‐electric power of hot carriers UT due to a high electric field E is investigated. Two cases are considered: 1) weak electric field (E ≦ 103 V/cm) and 2) high electric field (E ≧ 103 V/cm). The theory is developed for both cases in the approximation of the isotropic mass and quasi‐elastic scattering. Dc pulse measurements on n‐type germanium in a weak electric field yield a quadratic dependence of UT on the electric field strength. The experimental results are found to be in a satisfactory agreement with theory. In high electric fields the microwave technique is used. It is concluded that the energy relaxation for high‐energy electrons in n‐Ge is determined mainly by acoustical modes.
The Theory of Shallow F‐Centres
Authors: Perlin Yu. E. , Gifeisman Sh. N. 
Published: July 2007

AbstractA theory of hydrogen‐like impurity centres in ionic crystals in the presence of an external magnetic or electric field is developed. The coupling to longitudinal optical phonons is taken into account, and the results are valid for arbitrary interaction strength. Feynmans path‐integral representation for the partition function of the phonon‐impurity system and a variational principle connected with a quadratic trial Lagrangian are used. A simple expression for the bound polaron ground‐state energy with a single variational parameter is derived. Formulae for the magnetic and electric susceptibilities are obtained. The electron‐phonon coupling reduces essentially these susceptibilities in comparison with the results of a hydrogenic model.
On the Theory of Thermogalvanomagnetic Phenomena in Semiconductors at High Magnetic Fields
Authors: Kalashnikov V. P. , Zlobin A. M. 
Published: July 2007

AbstractThe transverse charge and heat flows of conduction electrons interacting with optical phonons at high magnetic fields are calculated. Explicit expressions for the diagonal elements of transport coefficients are derived taking into account the two‐stage mechanism of electron‐phonon scattering at low temperatures. The temperature and field dependences of these coefficients are obtained for the various cases.
Tensile Behavior upon Ordering of Ni3Fe Single Crystals
Authors: Victoria M. , Vidoz A. E. 
Published: July 2007

AbstractThe tensile properties of ordered and disordered Ni3Fe single crystals have been investigated. Also, polycrystalline specimens have been tested to show the influence of grain size on the deformation characteristics of Ni3Fe. Measurements have been made to determine the influence of parameters such as the initial orientation of the tensile axis of single crystals, the ordered domain size, and the test temperature on the mechanical properties of Ni3Fe. Tensile axis reorientation during deformation was followed with X‐ray techniques. It was found that in ordered single crystals, the measured tensile axis rotation agrees well with the calculated values if one activated glide system is assumed. The influence of secondary slip on the tensile characteristics of ordered crystals was determined by using specimens oriented for multiple glide. It is demonstrated that the work hardening rate increases with the occurrence of secondary slip. The strain‐aging phenomena shown previously in polycrystalline Ni3Fe was found to occur also in single crystals. The nature of the observed effects in ordered Ni3Fe is interpreted in terms of the antiphase boundary tube mechanism.
On the Work Hardening of Superstructures
Authors: Vidoz A. E. 
Published: July 2007

AbstractThe mechanism for the work hardening of superstructures proposed by Vidoz and Brown is modified. It is shown that this model explains the experimental results even when only a very small increase in the forest density, possibly too small to be observed experimentally, takes place during deformation. It is suggested that this small contribution of secondary slip may be due to a latent hardening effect. Analytical expressions for the stress to move primary and conjugate dislocation in a crystal are derived. The discussion shows that the antiphase boundary tube mechanism can explain most of the available experimental results.
Effect of Absorption on Multi‐Beam Intensity Profiles of Wedge Crystals
Authors: Sheinin S. S. , Cann C. D. 
Published: July 2007

AbstractThe effects of absorption on multi‐beam intensity profiles of wedge crystals have been investigated. The fringe spacing has been shown to change appreciably when absorption is taken into account, particularly at high accelerating voltages. It has also been shown that the subsidiary fringes which occur at certain values of the deviation parameters s in theoretical profiles which neglect absorption, will in some cases disappear when absorption is taken into account. Good agreement was found between these theoretical predictions and experimental measurements of extinction distance in magnesium oxide and molybdenum.
Cyclotron Resonance of Holes in Si
Authors: Owner‐petersen M. , Samuelsen M. R. 
Published: July 2007

AbstractHole resonances are studied in 3900 Ωcm p‐type Si samples at temperatures from 1.2 to 5.0 °K. Measurements are performed at 45 GHz using magnetic inductions B up to 10 kG corresponding to a maximum value of m*/m0 = 0.62, and a few resonances not reported previously are observed. The experimental data are in reasonably good agreement with the Luttinger theory [1] of Landau levels in the valence band of semiconductors when a suitable set of band parameters are chosen. Numerical calculations of the levels and the matrix elements for transitions between the levels are carried out for B pointing in the crystallographic directions [001], [111] and [110]. The variation of the level positions and of the matrix elements as a function of the band parameters is examined in order to find the parameters providing the best fit to the experimental data.
ESR Detection of Self‐Trapped Holes in AgCl
Authors: Höhne M. , Stasiw M. 
Published: July 2007

AbstractAg2+ centres are produced in doped and appropriately treated AgCl crystals by irradiation with blue light at 20 °K. It is shown that the only purpose of the preceding treatment is to create a high concentration of electron traps. In chalcogen doped crystals (AgCl:S, Se, Te) electron traps are formed by pre‐irradiation with blue light above 120 °K; in iron doped crystals the incorporated Fe2+ ions are converted to Fe3+, acting as traps, either by irradiation at 20 °C or by annealing in chlorine gas. As the paramagnetic data of the localized Ag2+ centres are independent of the kind of the impurity, one must conclude that the hole is trapped in the undisturbed lattice.
Negative Space‐Charge Effect on Schottky Current in Thin Insulating Films
Authors: Antula J. 
Published: July 2007

AbstractA simple theory is used to describe the effect of negative space‐charge on the Schottky current in thin insulating films. The space‐charge limited current is discussed as a limiting case. The theoretical results are applied to the measured In I (\documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt U $\end{document}) Schottky characteristics of Al‐Al2O3‐Al structures. The observed negative space‐charge effect leads to a concentration of trapped electrons nt ≈︁ 3 ×1017 cm−3.
Thermally Activated Domain Wall Movement in Nickel‐Iron Films
Authors: Craik D. J. , Wood M. J. 
Published: July 2007

AbstractThe slow movement of domain walls under a steady field, due to thermal activation, has been observed in a permalloy film, and a quantitative study made over the temperature range ‐39 to +77 °C. Unlike results obtained previously in another film [8], these do not conform to the simple theory. The theory is extended to include switching by a sinusoidal field, and the ac coercivities are correlated with the dc results. It is suggested that magnetic viscosity should be more pronounced in films with high magnetization dispersions. Some criticisms of the simple theory are advanced. An estimate of the frequency factor C is made from the results on both films, which is higher than theoretical predictions.
L'activation thermique des déviations sous faibles contraintes dans les structures h.c. et c.c. Par
Authors: Escaig B. 
Published: July 2007

AbstractDuesbery et Hirsch ont suggéré récemment que dans les structures c.c. et h.c., la déviation d'une dislocation hors de son plan de dissociation, doit se produire à faible contrainte par un mécanisme de double décrochement. On montre ici que ce mécanisme doit se produire en dessous d'une contrainte ßc = R/b2, où R est l'énergie de recombinaison et b le vecteur de Burgers de la dislocation; de plus, il n'introduit aucune discontinuité de contrainte, d'énergie, ou de volume d'activation. On calcule l'énergie d'activation maximum de la déviation correspondantà une composante thermique de la contrainte nulle, pour laquelle on retrouve l'expression donnée par Duesbery et Hirsch. En tenant compte de l'interaction élastique des décrochements au moyen d'une tension de ligne qui varie logarithmiquement aves leur distance de séparation, on obtient un volume d'activation qui varie en σ−1 à faible contrainte σ.
Étude de l'écoulement plastique de monocristaux filamentaires de fer entre 300 et 4 °K Par
Authors: Conte R. , Groh P. , Escaig B. 
Published: July 2007

AbstractOn étudie du point de vue expérimental l'influence de la température et de la vitesse de traction sur la plasticité de monocristaux filamentaires de fer, dans un domaine de température allant de 4 à 300 °K. Les résultats des mesures sont comparés aux prédictions du modèle de Dorn et Rajnak (forces de Peierls) et à celles du modèle d'Escaig (dissociation‐recombinaison). Ce dernier modèle semble mieux rendre compte de l'expérience, indiquant que les “barrières de potentiel de Peierls” sont probablement dues, dans la structure cubique centrée, à un effet de dissociation des dislocations.
Quantum‐Mechanical Treatment of the Transient Processes with Three‐Magnon Non‐Linear Transitions under Perpendicular Pumping
Authors: Le Gall H. 
Published: July 2007

AbstractThe transient growth of spin‐wave populations with three‐magnon non‐linear processes under perpendicular pumping is studied. Calculations are made on the basis of second quantization of the magnetic system and the pumping microwave field, assuming that the magnons are in thermal distribution before the electromagnetic pulse is applied. General expressions describing transient evolution of the uniform mode and the parametric states are established in the case where the coincidence condition is satisfied (occurrence of the three‐magnon transitions at resonance). The stationary state of the parametric magnons is also determined. To test experimentally the validity of the theory an expression for the transient power absorbed by the crystal at the beginning of the parametric excitation of the quasiparticles is derived. Basing on experimental data, the limits of the applicability of the theory are discussed.
Couplage ferro‐antiferromagnétique et traînage magnétique dans des couches minces multiples CoCoO et NiNiO Par
Authors: Schlenker C. 
Published: July 2007

AbstractOn a étudié le couplage ferro‐antiferromagnétique sur des couches minces polycristallines, à anisotropie uniaxiale, oxydées superficiellement, du type CoCoO ou NiNiO, entre _ 190 et 20 °C. L'anisotropie unidirectionnelle s'annule à une température de transition toujours inférieure au point de Néel et liée à l'épaisseur moyenne de la couche antiferromagnétique. L'anisotropie uniaxiale n'est pas modifiée par la présence du couplage. On explique le maximum du champ coercitif et la disparition de l'hystérésis de rotation au voisinage de la température de transition en supposant que la couche antiferromagnétique “déformable” du point de vue magnétique aux basses températures, devient “rigide” aux plus hautes températures. On observe un traînage magnétique de très grande amplitude qui provient de réorientations des moments dans certains grains antiferromagnétiques et suit une loi logarithmique dans des intervalles de temps de plusieurs heures, par suite de la dispersion de la taille des grains. Les ordres de grandeur de l'anisotropie antiferromagnétique déduits de l'étude détaillée du traînage sont supéieurs à l'anisotropie magnétocristalline des oxydes à l'état massif.
Absolute Atomic Scattering Factors of Tungsten
Authors: Paakkari T. , Suortti P. 
Published: July 2007

AbstractThe atomic scattering factors f of tungsten are determined in the region sin θ/λ ≤ 1.1 Å−1from the integrated intensities of Bragg reflections. The reflections from a powder sample were measured at 300 °K with monochromatic MoKα radiation. The intensities are corrected for the effects of porosity and surface roughness, and for the contribution of thermal diffuse scattering. The intensities are put on an absolute scale with respect to the absolute value f(110) of iron. The mass absorption coefficient of tungsten for MoKα radiation is measured to be μQ = (101.8± 0.4) cm2/g. A value for the temperature parameter of BW = (0.183±0.008) Å2 is obtained by a measurement of the integrated intensity of a high‐order reflection both at 300 and 78 °K. This corresponds to the Debye temperature θM = (325 ∓ 7) °K. The experimental f‐values are compared with various theoretical calculations. It is found out that the Dirac‐Slater values are in excellent agreement with present results.
Empirical Third Neighbour LCAO Energy Bands of Silicon
Authors: Alstrup I. , Johansen K. 
Published: July 2007

AbstractA third nearest neighbour LCAO description, including overlap integrals, is constructed for the energy bands of silicon. The overlap integrals are calculated from Slater‐type atomic orbitals, the interaction integrals and the screening parameter are determined empirically by fitting the bands to recent adjusted OPW calculations. Good overall agreement is obtained. The second nearest neighbour interaction integrals obtained cannot be derived from two‐center integrals only. Previous failures to obtain reasonable bands for diamond and silicon by the empirical LCAO scheme are briefly discussed.
Stacking Faults on {110} Planes in the B.C.C. Lattice
Authors: Pegel B. 
Published: July 2007

AbstractMaximum stacking fault energies for α‐type stacking faults in the b.c.c. lattice are estimated for the group Va and VIa transition metals and iron. The half widths of glissile type split screw dislocations should be in all cases at least one total Burgers vector.
Thermal Expansion of Cubic Metals in Krebs's Model
Authors: Singh A. K. , Sharma P. K. 
Published: July 2007

AbstractA calculation of the temperature dependence of the Grüneisen parameters for copper, silver, gold, aluminium, sodium, and potassium is carried out starting from the experimental values of the pressure dependence of the elastic constants using Krebs's model for the lattice dynamics of metals. Houston's six‐term integration procedure is used in evaluating the integrals over the phonon spectrum. The calculated γ‐T curves show fairly satisfactory agreement with experiment for copper, but not for other metals.
Temperature Dependence of the Diffusion of Photoexcited Holes in AgBr
Authors: Georgiev M. , Zagorska E. , Malinowski J. 
Published: July 2007

AbstractA detection technique based on the bleaching of a thin silver deposit is used to investigate the diffusion of photoinduced holes between ‐35 and +35 °C. The apparent diffusion coefficient is found to follow an Arrhenius‐type temperature dependence exhibiting an activation energy of 0.53 eV. Following previous suggestions, it is again concluded that the holes become engaged in multiple trapping while migrating within the crystal lattice. Some trapping models are discussed.
Der Beitrag der Versetzungen zur Anisotropie des magnetischen Einmündungsgesetzes in Nickel
Authors: Holz A. , Kronmüller H. 
Published: July 2007

AbstractDas magnetische Einmündungsgesetz bei Anwesenheit von Stufenversetzungen wird in Abhängigkeit von der Magnetfeldrichtung für Nickel als numerisches Beispiel berechnet. Die Suszeptibilität läßt sich in einen streufeldfreien Anteil und einen vom Streufeld hervorgerufenen negativen Beitrag zerlegen. Numerische Rechnungen wurden für die durch Burgersvektor, Gleitebenennormalen und Versetzungslinien bestimmten Ebenen ausgeführt. Im Bereich bis 2000 Oe wird in allen drei Ebenen eine ausgeprägte Anisotropie gefunden, die im wesentlichen durch bestimmt ist. Mit großem Magnetfeld H nimmt proportional 1/H4 ab, während nur mit 1/H3 abfällt. Im Feldbereich H ≥ 4 π Is ist deshalb die Anisotropie von X vornehmlich durch bestimmt.
Behaviour of the High‐Field Domains below the Voltage of the Nucleation Threshold
Authors: Levinstein M. E. , Shur M. S. 
Published: July 2007

AbstractOn the basis of the phenomenological theory it is shown that the high‐field domain in a Gunn diode does not annihilate if the applied voltage becomes lower than the threshold for domain nucleation. The dependence of the threshold for domain annihilation on the diode parameters is obtained. It is found that the domain annihilation amplitude is equal to half of the domain amplitude when the applied voltage corresponds to that at the beginning of the region of negative differential resistivity in the diode. The results obtained are important if an additional microwave voltage is applied, for example if the diode operates in a resonator.
The Correlation Function Szz (ω) for Weakly Coupled Impurity Atom Spin in a Ferromagnetic
Authors: Krivoglaz M. A. , Kvashnina L. B. 
Published: July 2007

AbstractThe closed chain of equations for the temperature Green's functions for the z‐th component of the spin of an impurity atom in a ferromagnetic is obtained for the case of quasi‐local spin excitations in the neighbourhood of the impurity atom. The solution of this system is obtained in explicit form for the cases of high and low temperatures and of small values of the spin of the impurity atom (S = 1/2, 1, 3/2). For these cases the spectral representation Szz(ω) of the correlation function 〈Sz(t1) − Sz, Sz(t2) − Sz〉 of the impurity atom spin is determined. It is pointed out that the quasi‐local spin states can result in a modulational broadening of the line of nuclear magnetic resonance some orders of magnitude larger than the broadening due to the spin waves in the perfect crystal.
Analysis of Point Defect States in Copper II. The Effects of Stage I and Stage III Annealing on Electron‐Irradiation‐Induced Frenkel Pairs
Authors: Dworschak F. , Schuster H. , Wollenberger H. , Wurm J. 
Published: July 2007

AbstractThe point defect states before and after stage I and stage III annealing are compared by means of 80 °K damage rate measurements. The results can be interpreted most easily by vacancy migration in stage III or more artificially by the conversion of the “stage III interstitial” to a third modification. The stage I annealing results in an at least partial formation of stable di‐interstitials.
Evidence of a Doubly Ionized Native Donor in CdTe
Authors: Whelan R. C. , Shaw D. 
Published: July 2007

AbstractThe electrical conductance of CdTe has been measured in the temperature range 490 to 950 °C as a function of the ambient partial pressure of Cd, pCd. The conductance varied as p and was interpreted in terms of a doubly ionized native donor whose associated ionization energy was estimated to be ≦ 0.24 eV. The incorporation energy of the doubly ionized donor into the CdTe lattice was (1.65 ± 0.15) eV. Defect equilibrium occurred by a bulk diffusion process possessing different characteristics to radiotracer self‐diffusion processes.
Piezoresistance of Tellurium II. Experiments with Pressures Lowering Symmetry
Authors: Herrmann K. H. , Puhlmann J. 
Published: July 2007

AbstractThe eight independent piezoresistance coefficients of tellurium single crystals containing acceptors with concentrations from 5.8 × 1014 cm−3 to 4.9 × 1017 cm−3 are measured. In the extrinsic region all coefficients are independent of temperature. This contradicts a many‐valley structure of the valence band. The anisotropy of the piezoresistance effect is strongly affected by structural defects.
The Electronic Structure of CdO II. Spectral Distribution of Optical Constants
Authors: Altwein M. , Finkenrath H. , Koňák Č. , Stuke J. , Zimmerer G. 
Published: July 2007

AbstractThe reflectivity of CdO has been measured up to 13 eV on single crystals and polycrystalline material. Moreover the absorption of thin films was studied. The frequency dependence of the optical constants evaluated by Kramers‐Kronig analysis is discussed with regard to the band structure calculated by Maschke and Rössler [1]. The investigation of the shape of the intrinsic absorption edge and the measurements of the electrical conductivity on films with low electron concentration indicate the existence of an indirect gap.