bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of Boron‐Nitride Fibers
Authors: van Torne L. I.
Published: July 2007

A transmission electron microscopy and electron diffraction investigation of BN fibers 5 to 7 μm in diameter indicates that the structure can be interpreted in terms of atomic disorder over distances comparable to the atomic spacing. Thermal conductivity considerations suggest that the disorder results from the “quenching in” of thermally induced atomic vibrations.
Extension of the Howie‐Whelan Equations for Electron Diffraction to Non‐Centro Symmetrical Crystals
Authors: Gevers R. , Blank H. , Amelinckx S.
Published: July 2007

The Howie‐Whelan system of equations [2] is extended to non‐centro symmetrical crystals. This system of equations, which is valid for the Laue case, describes the scattering of electrons by a perfect crystal in the two‐beam approximation and takes anomalous absorption into account. The theory predicts that Friedel's law no longer holds for the dark field image but is still valid in the bright field. Observations on 180° walls in barium titanate support the theory. In addition the theory shows that 180° walls in inclined planes should produce α‐type fringes. This phenomenon is also observed experimentally.
Ordering of Interstitial Impurities in Niobium
Authors: van Landuyt J. , Gevers R. , Amelinckx S.
Published: July 2007

The ordering phenomenon in niobium is studied by electron microscopy and by electron diffraction. The phenomenon is found in parts of niobium foils subjected to an annealing treatment in vacuum. Domains are formed which, on the basis of the present model, are due to the ordering of interstitial oxygen atoms. The insertion of the interstitials on a superlattice in the nobium matrix causes a deformation of the latter in a 〈110〉 direction. The domain structure results from the fact that several orientations are possible for the superlattice. Further evidence for this ordering is deduced from the presence of superlattice dislocations and of supplementary spots in the diffraction patterns. The superlattice is deduced from the diffraction data and a composition Nb2O is attributed to this metallic oxide phase. The domains are revealed by fringe contrast at the boundaries and by the change in background intensity. Both contrast effects are associated with the slight deformation due to the ordering. A discussion is included of a second type of fringe pattern which is often observed in annealed niobium. Patterns of this type have previously been attributed to the presence of stacking faults; it is shown here that they are due to plate‐shaped precipitates of some oxide phase in the niobium matrix.
Remarks on the Recombination of Electrons and Donors in n‐Type Germanium
Authors: Beleznay F. , Pataki G.
Published: July 2007

The cascade theory of the recombination of electrons into ionized donors is critically examined in this paper. It is shown that in Lax's model, and also in the work of Hamann and McWhorter, the neglect of lower lying states leads to an overestimate of overestimate of the sticking probability. It is also shown, that the model proposed by Ascarelli and Rodriguez ‐ which neglects the higher excited states ‐ does not lead to the experimental value for the total capture cross‐section.
Umverteilung heißer Elektronen auf die Täler des Leitungsbandes von Silizium
Authors: Asche M. , Bondar W. M.
Published: July 2007

Es wird eine Möglichkeit zur Abschätzung der Elektronenumverteilung auf die Täler in Vieltalhalbleitern bei elektrischen Feldern gezeigt. Sie ist auf der Änderung der Besetzungszahlen der Täler bei Druck begründet. Experimente wurden an 20 Ωcm n‐Si bei 77°K durchgeführt und entsprechend ausgewertet. Die Resultate stimmen qualitativ mit den Daten aus Anisotropiemessungen der Leitfähigkeit überein.
Untersuchungen an halbleitenden Indiumoxydschichten
Authors: Groth R.
Published: July 2007

Nach dem „Sprühverfahren”︁ wurden n‐leitende Indiumoxydschichten mit Schichtdicken zwischen 0,1, und 0,5 μm auf Glasplatten hergestellt und die Herstellungsbedingungen dieser Schichten untersucht. Die Leitfähigkeit der Schichten liegt je nach Dotierung zwischen 1,5 × 102 und 4,3 × 103 Ω−1cm−1 und die Konzentration and freien Ladungsträgern zwischen 1019 und 6 × 1020 cm−3. Die Beweglichkeit der freien Ladungsträger hängt erheblich von der jeweiligen Dotierung ab und wird vermutlich durch Streuung an den Korngrenzen der mikrokristallinen Schicht bestimmt. Die Schichten sind im sichtbaren Spektralbereich absorptionsfrei und zeigen im Ultrarot wegen der hohen Konzentration freier Ladungsträger ein hohes Reflexionsvermögen.
L'approche à la saturation de l'aimantation des corps ferromagnétiques polycristallins de structure cubique
Authors: Vergne R.
Published: July 2007

L'auteur établit l'expression de la loi d'approche à la saturation de l'aimantation des corps ferromagnétique polycristallins de structure cubique sous la forme d'un développement en série qu'il pousse jusqu'au terme en H−3. Il introduit l'interaction magnétique des cristallites et tient compte de K2 dans l'expression de l'énergie magnétocristalline. Il compare ensuite quantitativement la théorie et l'expérience dans le cas du fer et du nickel.
The Influence of External Electric Fields on the Absorption of Ag+ ‐Centres in KCl (I)
Authors: Gebhardt W. , Mohler E.
Published: July 2007

A method of measuring the transverse Stark effect of point defect absorption in ionic crystals at low temperatures is described. The absorption bands of KCl: Ag+ in the UV region show an increase in the oscillator strength of about Δf/f ≈ 8 × 10−4 and a shift, predominantly to the low energy side, of about Δε ≈ 8 × 10−6 eV under external fields of 105 V/cm.
The Temperature Dependence of the F‐Centre Absorption and Emission in Five Alkali Halides
Authors: Gebhardt W. , Kühnert H.
Published: July 2007

The temperature dependence of the F‐centre absorption and emission bands in NaCl, KCl, RbCl, KBr, and KI is measured. The peak energies and half widths at T = 0°K, the effective phonon frequencies, and the parameters of the maximum shift are determined.
Trapping of Holes in Silver Bromide Single Crystals
Authors: Platikanowa W. , Malinowski J.
Published: July 2007

The reaction between a deposit of silver and neutral bromine formed by holes migrating to the surface of a silver bromide crystal is used to investigate the concentration decay of holes in the interior of the crystal. The effective lifetime of photoexcited holes in a thin surface layer is shown to be at least an order of magnitude larger than the bulk lifetime. Thermal annealing of the samples substantially increases the bulk trapping rate whilst leaving the surface rate unchanged. The observations are explained in terms of a layer of adsorbed bromine formed at the surface of the crystal during exposure. It is shown that an effective bromine acceptor is necessary for the formation of a stable surface latent image. No relation is found between the lifetimes of photoexcitedle ectrons and holes, which suggests that these carriers do not recombine with one another. The nature and concentration of the trapping centres and the effect of annealing the crystals is discussed.
Radiation Annealing in Cuprous Oxide
Authors: Vajda P.
Published: July 2007

Experimental results from high‐intensity γ‐irradiation of cuprous oxide are used to investigate the annealing of defects with increasing radiation dose. The results are analysed on the basis of the Balarin and Hauser [3] statistical model of radiation annealing, giving a square‐root relationship between the rate of change of resistivity and the resistivity change. The saturation defect density at room temperature is estimated on the basis of a model for defect creation in cuprous oxide.
NMR Evidence for Contact Hyperfine Coupling in Paramagnetic UF4
Authors: Pintar M.
Published: July 2007

The F19 NMR absorption in powdered UF4 is investigated in the temperature range 122 to 433 °K at magnetic fields between 10000 and 5000 G. The fluorine absorption pattern in this paramagnetic material with seven nonequivalent F‐sites in the unit cell is reproduced qualitatively by a sum of six asymmetric component lines (H∥ ‐– H⊥)−1/2 × (H–H⊥)−1/2, some of which are shifted in the high field direction, and some in the low field direction. The occurrence of low‐field shifted components provides evidence of contact hyperfine interaction between the magnetic electrons and the fluorine nuclei whereas the occurrence of high‐field shifted components may arise from indirect coupling through electron transfer, and indicates partial covalent bonding between the magnetic electrons and the surrounding fluorine ions. This is supported by magnetic susceptibility and EPR data.
Effect of Hydrostatic Pressure on the Elastic Behavior of Cubic Crystals
Authors: Ghate P. B.
Published: July 2007

Finite deformation theory is used to calculate the effective second order elastic constants (cik′) of a cubic crystal subjected to very high pressures. We obtain cik′ = cik + A η + B, where A and B depend on the second order and higher order elastic constants and η depends on the pressure.
Paramagnetic Resonance of Pt3+ Ions in BaTiO3 Single Crystals
Authors: Šimánek E. , Šroubek Z. , Žďánský K. , Kaczér J. , Novák L.
Published: July 2007

The paramagnetic resonance of Pt3+ ions in niobium doped BaTiO3 single crystals is investigated at a temperature of 4 °K. The hyperfine parameter A is found to be (0 ± 5) × 10−4 cm−1. The hyperfine field resulting from core polarization by the unpaired 5d‐electrons in platinum is deduced using this value.
Experimental Investigation of Some Features of Incoherent Rotation in Thin Permalloy Films
Authors: Telesnin R. V. , Ilicheva E. N. , Kolotov O. S. , Nikitina T. N. , Pogozhev V. A.
Published: July 2007

Some features of the mechanism of inhomogeneous rotation in thin permalloy films, reversed by pulse fields are investigated: switching coefficient, threshold fields, parameters of transitions to fast magnetic reversal. The behaviour of the films are also investigated for fields applied along the “hard” axis. The results are compared with static parameters of thin films: anisotropy field, angular dispersion and domain structure.
Der vektorielle Photoeffekt an Kalium
Authors: Brauer M.
Published: July 2007

An im Hochvakuum aufgedampften dicken, polykristallinen Kaliumschichten wird mit linear polarisiertem Licht im Energiebereich zwischen 2,25 und 5,20 eV die Winkelabhängigkeit der Ausbeute des äußeren Photoeffektes gemessen. Für alle Einfallswinkel Θi und für beide Orientierungen des elektrischen Vektors E ergibt sich dabei stets ein Maximum für einfallendes Licht der Energie ℏω = 3,1 eV. Der selektive Effekt Yp(ℏω, Θi) (E parallel zur Einfallsebene) ist immer größer als der normale Effekt Ys (ℏω, Θi) (E senkrecht zur Einfallsebene) und durchläuft für jede Frequenz in Abhängigkeit vom Lichteinfallswinkel einen Maximalwert, während der normale Effekt für Frequenzen in der Nähe der langwelligen Grenze mit steigendem Einfallswinkel monoton fällt; für größere Werte von ℏω weist jedoch auch der normale Effekt ein Maximum auf. Durch Bildung des Quotienten Yp/Ys erhält man den sogenannten Vektoreffekt der Ausbeute, der sowohl in Abhängigkeit von der Frequenz als auch vom Einfallswinkel einen Maximalwert durchläuft. Die experimentellen Ergebnisse werden abschließen diskutiert.
Impurity Scattering in the Theory of Interband Magneto‐Optical Effects
Authors: Korovin L. I. , Kharitonov E. V.
Published: July 2007

The quantum theory of the line‐shape of oscillatory interband magneto‐optical effects in the region of the intrinsic absorption edge in semiconductors is developed for the case of non‐stationary electron states arising from the scattering of electrons by an impurity atom with a short‐range (repulsive) potential. The peculiarity of the problem is that a first‐oder perturbation treatment of the interaction parameter is inadequate, and in order to obtain finite expressions for the function −iW = Λ + iΓ in the vicinity of resonance it is necessary to sum an infinite series which represents the individual terms of the kinetic equation. The cases of low impurity‐atom concentration and high concentration with weak interaction (when the one‐particle approximation is still valid) are considered in detail. −iW is found to depend, in general, on the concentration of charge carriers, their interaction with impurity atoms, the frequency of the light, the electron momentum, and various parameters of the band structure.
Bitter Patterns on Nickel Ferrite Single Crystals
Authors: Rosenberg M. , Tânâsoiu C. , Nowicki L.
Published: July 2007

The Bitter patterns on the (111) and (110) natural faces of nickel ferrite single crystals, grown by the flux melt method, are investigated. The internal domain structure consists of three sets of parallel domains magnetized along the [111], [111] and [111] directions and separated in each set by 180° Bloch walls and by 71° walls between sets. The complex structure of the Bitter patterns on the (111) plane is due to the tendency for domains of reverse magnetization to be formed. The magnetization process involves both displacement and rotation of the walls.
Substructure of Persistent Slip Bands in Cyclically Deformed Copper
Authors: Lukáš P. , Klesnil M. , Krejčí J. , Ryš P.
Published: July 2007

The dislocation distribution in the surface layer of cyclically deformed specimens of polycrystalline copper is studied by means of transmission electron microscopy of thin foils, both parallel and nonparallel to the surface. The distribution within the surface layer and near the persistent slip bands is found to differ considerably from that inside the specimens. The persistent slip bands consist of zones of alternately high and low dislocation density. The zones of high density link together at a particular depth below the surface. The zones of low density are assumed to serve as “channels” in which the motion of dislocations emitted from Frank‐Read sources is relatively free. The escape of these dislocations from the free surface results in surface extrusions.
Theory of Space‐Charge‐Limited Currents in Thin Semiconductor Layers
Authors: Geurst J. A.
Published: July 2007

The current flowing in a thin semiconductor layer between two knife‐like contacts located on the same side of the layer is analyzed using a model in which the thicknesses of the layer and the electrodes are taken to be negligible compared with the separation of the electrodes. Since the excess density of mobile charge in the layer is controlled by the transversal component of the electric field, side effects play a dominant part in the model. The calculated current‐voltage characteristic shows a transition from ohmic to space‐charge‐limited behaviour at increasing voltages. The space‐charge‐limited current at higher voltages is inversely proportional to the square of the electrode distance. This dependence was found experimentally by Polke, Stuke and Vinaricky. The effect of traps is taken into account by means of a simple model. If empty traps are present at zero electric field, the theory yields a threshold potential beyond which the current starts flowing.
Neutron Investigation of Temperature Effects in the Magnon Spectrum of Magnetite
Authors: Dimitrijević Ż. , Kraśnicki S. , Rżany H. , Todorović J. , Wanic A.
Published: July 2007

The diffuse magnon scattering peaks connected with τ = (111) in magnetite are examined at a number of temperatures using neutrons with λ = 1.314 Å. The decrease in magnon energies at elevated temperatures is observed and compared with the theory of Mills et al. [10]. Pronounced temperature dependent asymmetry of the magnon low energy peak is found.
Mößbaueruntersuchungen an Co57‐dotiertem AgCl
Authors: Hennig K. , Meisel W. , Schnorr H.
Published: July 2007

Mößbaueruntersuchungen bei 77, 195 und 297 °K an Co57‐dotierten AgCl‐Polykristallen lieferten folgende Ergebnisse: Die bei 77 und 195 °K auftretenden Spektren können durch Fe++, das auf Kationenplatz eingebaut und mit einer Kationenlücke assoziiert ist, gedeutet werden. Die auf reines Eisen bezogene Isomerieverschiebung beträgt (1,32 ± 0,05) mm/s bzw. (1,25 ± 0,05) mm/s und die Quadrupolaufspaltung (1,07 ± 0,07) mm/s bzw. (0,74 ± 0,07) mm/s für 77 bzw. 195 °K. Bei 297 °K, beträgt die Isomerieverschiebung (1,15 ± 0,05) mm/s, die Quadrupolaufspaltung ist kleiner als 0,3 mm/s. Das anomale Verhalten der Quadrupolaufspaltung bei 297 °K wird durch eine genügend schnelle Rotation der Kationenlücke um Fe++ gedeutet. Die Ergebnisse werden mit bekannten Werten für Co57‐dotiertes NaCl verglichen und die auftretenden starken Abweichungen diskutiert.
Wechselwirkungen und Verteilungskurven hartmagnetischer Teilchenkollektive
Authors: Henkel O.
Published: July 2007

Es wird experimentell gezeigt, daß bei hartmagnetischen Teilchenkollektiven ohne Wechselwirkung die Verteilung log‐normal ist. Wenn die ermittelten Abweichungen bei praktischen Kollektiven auf die Wechselwirkungen der Teilchen untereinander zurückgeführt werden, lassen sich Angaben über die Art und Größe der Wechselwirkungsfelder machen. In der Regel bestehen sie aus einem positiven, magnetisierungsunabhängigen und einem negativen, magnetisierungsunabhängigen Term. Bei Cu‐Ni‐Fe‐Legierungen läßt sich die Wechselwirkung in 1. Näherung sogar nur durch den magnetisierungsunabhängigen Term beschreiben.
Origin of Quadrature Flux in Magnetic Films
Authors: Harte K. J. , Cohen M. S. , Weiss G. P. , Smith D. O.
Published: July 2007

Several investigators have studied flux varying in quadrature with a small ac field applied to a magnetic film in the presence of a perpendicular dc field, i.e., the imaginary part of the susceptibility. This phenomenon has often been interpreted as arising from magnetic switching in scattered regions where the net field crosses the tip of either uniaxial, complex biaxial, or negative anisotropy astroids. The viewpoint taken here, however, is that the quadrature flux originates in local irreversible reorientations of the magnetization ripple. This model is supported by experiments in which quadrature flux was measured as a function of dc field magnitude for three different field configurations chosen so that for a given field value the ripple state was the same in the three configurations.
Changes in Ag2O Films
Authors: Rollins T. L. , Weichman F. L.
Published: July 2007

Thin films of Ag2O were deposited on a cooled substrate by cathodic sputtering of silver in a low pressure oxygen atmosphere. The effects of ageing at room temperature and the effects due to slight heating in air are studied through the changes of electrical resistance, optical absorption and photoconductivity. It is proposed that the fresh films contain a greater excess of oxygen over the stoichiometric Ag2O than the final higher resistance material. Unless mechanically disturbed, the films did not reduce to silver over periods up to one year.
Crystal Symmetry and Magnetic Structures
Authors: Verschueren M.
Published: July 2007

Symmetry considerations are used to determine the possible magnetic structures for a given crystal. The magnetic moment density is defined in two ways: (1) from the quantum mechanical definition of spin density, (2) from the classical concept of an array of magnetic moments. Since both definitions should have the same transformation properties, restrictions can be placed on the possible magnetic structures. Some applications of this theory are suggested.
Strahlungsdefekte in deuteronenbombardierten CdS‐Kristallen
Authors: Schweinberger W. , Wruck D.
Published: July 2007

An CdS‐Einkristallen wurden vor und nach einer Bestrahlung bei 150 °K mit 13,5 MeV‐Deuteronen Untersuchungen der Dunkelleitfähigkeit, der spektralen Verteilung der Photoleitfähigkeit, der Lebensdauer der Leitungselektronen und des Hafttermspektrums durchgeführt. Die Konzentration der durch Kernumwandlungen erzeugten Fremdatome Indium und Zinn wurde durch γ‐Spektroskopie ermittelt. Aus den elektrischen Messungen folgt, daß durch den Beschuß mit einer effektiven Erzeugungsrate von ca. 5 × 10−3 cm−1 Defektniveaus bei Ec – 0,10 eV, Ec –0,42 eV und Ec –0,65 eV mit Einfangquerschnitten für Elektronen von 5 × 10−15, 1 × 10−14 bzw. 5 × 10−14 cm2 gebildet werden, die bei Raumtemperatur stabil sind. Das Zentrum bei Ec –0,42 eV tritt sowohl als Haftterm als auch als Donator in Erscheinung. Das Verhalten der Lebensdauer deutet auf die Vergrößerung der Konzentration von “class II” Rekombinationszentren bei ca. Ey + 0,15 eV hin. Es wird eine Deutung hinsichtlich der Natur der strahlungserzeugten Defektniveaus vorgeschlagen.
Stacking Faults in TiC
Authors: Venables J.
Published: July 2007

TiC single crystals doped by diffusion with 100 ppm of boron have been examined by transmission electron microscopy. Stacking faults, approximately 1 μm wide, bounded by partial dislocations were observed in all doped samples. It is considered that the faults serve as nucleation sites for the “Mondrian precipitates” observed by Williams [1].
Ferroelectric Properties of Solid Solutions of Triglycine Sulfate and Fluoberyllate Crystals
Authors: Březina B. , Šafránková M. , Kvapil J.
Published: July 2007

A series of solid solutions of ferroelectric TGS and TGFBe single‐crystals are prepared by crystallization from aqueous solutions. This procedure allows the phase transition from the ferroelectric to the paraelectric state to be varied in the temperature range 48.5 to 70°C. The temperature of the phase transition is not a linear function of the composition of the mixed single‐crystals. The temperature dependence of the permittivity of solid solutions of all concentrations obeys the Curie‐Weiss law.
Theoretical Phonon Spectra and Heat Capacities of Solidified Argon and Krypton
Authors: Gupta N. P. , Dayal B.
Published: July 2007

The phonon spectra of solidified Argon and Krypton have been calculated on the basis of the Born‐Karman theory using the interatomic potential ϕ(r) = ‐Ar−6 + AB × exp (‐r/Q), and taking into account the zero‐point energy and interactions of the four nearest neighbours. The evaluation of the parameters A, B, and Q requires a knowledge of the vibration spectrum of the crystal which is itself a function of these constants. A method of iteration is therefore employed to evaluate the potential parameters, after estimating the frequency‐dependent terms using the Debye theory of specific heats. The static lattice energy is obtained by a method of successive approximations. The specific heats and (θ,T) curves show a fair agreement with the experimental results.
Magnetic Susceptibility of Iron‐Rich Face‐Centered Cubic Iron‐Palladium Alloys
Authors: Arajs S.
Published: July 2007

Mass magnetic susceptibility of f.c.c. iron‐palladium alloys containing 1.0, 3.0, 4.9, 7.9, 10.0, 11.9, and 15.3 at% palladium has been measured up to 1500 °K. These alloys and pure f.c.c. iron do not follow the Curie‐Weiss law. The 1/τT vs. 1/T plots, where τ is the magnetic susceptibility and T the absolute temperature, reveal indirectly the antiferro‐magnetic nature of iron. The antiferromagnetic interaction is gradually reduced by alloying with palladium.
Transition Radiation from Three‐Layered Foils
Authors: Steinmann W. , Wille H.
Published: July 2007

A general expression is derived for the transition radiation from a foil consisting of three different layers with arbitrary dielectric constants and thicknesses. This expression is used to calculate transition radiation from oxide‐covered Al foils. The results are compared with the experimental data of Herickhoff et al. [7]. Almost perfect agreement between theory and experiment can be achieved if the oxide layers are taken into account.
Energieverluste schneller Elektronen in Alkalihalogenidschichten und ihre Winkelabhängigkeit
Authors: Geiger J. , Odelga P. , Pfeiffer H.‐Chr.
Published: July 2007

Die Energieverlustspektren schneller Elektronen nach dem Durchgang durch Alkalihalogenidschichten wurden aufgenommen. Ein Energieverlust in jedem Spektrum stimmt mit dem Wert überein, der sich formal aus der Plasmafrequenz freier Valenzelektronen ergibt. Die experimentelle Überprüfung der Dispersionsbeziehung zeigt jedoch, daß der Betrag der betreffenden Energieverluste innerhalb der Meßgenauigkeit vom Streuwinkel unabhängig ist, im Gegensatz zu den Messungen von Sueoka [3]. Daher können diese Energieverluste nicht auf der Anregung freier Elektronen beruhen. Die Intensität der unter‐suchten Energieverluste nimmt mit steigendem Streuwinkel etwa proportional zu ϱ−2 ab.
Dissociation of Dislocations on {110} Planes in Anisotropie B.C.C. Metals
Authors: Vítek V.
Published: July 2007

The dissociation of dislocations with Burgers vectors 1/2〈111〉 and 〈100〉 on {110} planes in b.c.c. metals is studied. An analysis of the possible dissociations is carried out for eleven b.c.c. metals using anisotropic elasticity theory. For those dissociations which are found to be energetically favourable, the widths of the extended dislocations are computed as functions of the stacking fault energy.
Atomic Motion in Hydrogen‐Bond Ferroelectrics
Authors: Villain J. , Stamenković S.
Published: July 2007

Anharmonic atomic motion in ferroelectrics may, in certain cases, be described in terms of a harmonic scheme by introducing a quasi‐spin formalism. In this paper the frequency spectrum is investigated first at zero temperature, using a spin‐wave approximation, then at finite temperatures, using a molecular‐field approximation and neglecting damping and its consequences. The results are discussed with reference to neutron scattering experiments, and a brief description of the critical phenomena is given.
Minoritätsträger in CdS I. Photospannung bei optischer Anregung innerhalb und außerhalb der Eigen‐absorption als Minoritätsträgereffekt
Authors: Palz W. , Ruppel W.
Published: July 2007

Die stationäre Leerlauf‐Photospannung in den untersuchten monokristallinen CdS‐Proben wird durch Erzeugung freier Minoritätsträger d. h. Löcher hervorgerufen. Dies wird auch für Belichtung mit Wellenlängen jenseits der Absorptionskante gezeigt, indem die Photospannung mit der Tilgung der Majoritätsträger‐Photoleitung verglichen wird. Aus der Beobachtung einer reversiblen Tilgung der Photoleitung, durch Belichtung jenseits der Absorptionskante erzeugt, wird geschlossen, daß unter diesen Bedingungen freie Majoritätsträger nur durch einen Zweistufenprozeß erzeugt werden, während freie Minoritätsträger in einem Einstufenprozeß aus diskreten Termen angeregt werden können. Wenn zusätzlich zu einer Photospannung, die durch Belichtung in der Nähe der Absorptionskante erzeugt wird, eine Photospannung durch eine Belichtung mit längeren Wellen hervorgerufen wird, stimmt die Beziehung zwischen diesen Spannungen quantitativ mit einer Theorie überein, die auf der Erzeugung einer Photospannung durch freie Minoritätsträger im Photoleiter beruht. Während die stationäre Photospannung am Metall‐CdS Kontakt allein durch Berücksichtigung der Minoritätsträgererzeugung verstanden werden kann, erfordert die Erklärung des Kurzschluß‐Photostromes die Berücksichtigung der freien Majoritäts‐ sowie Minoritätsträger.
Linear Equations for the Green's Functions of Crystal Lattices. A Possibility of Approximate Calculation
Authors: Kunc K.
Published: July 2007

Consideration of translational and rotational symmetry substantially reduces the number of Green's functions (elements of reciprocal dynamical matrix), which must be computed. In the present paper a method is proposed which further reduces this number by finding a set of linear equations for the Green's functions; these sets are given for b.c.c. and s.c. lattices. A method for approximate calculation of Green's functions is also proposed.
On the Infra‐Red Absorption of Crystals Due to Lattice Vibrations
Authors: Wehner R.
Published: July 2007

The theory of the infra‐red absorption and dispersion of crystals due to lattice vibrations is reinvestigated. Dipole moments up to third order and cubic and quartic anharmonicity in the displacements of the nuclei are considered. Using Green functions and the functional method of Martin and Schwinger a dispersion formula is derived in terms of renormalized phonons. The introduction of a renormalized linear dipole moment causes the oscillator strength to become a complex function of frequency. In the case of diatomic ionic crystals the frequency shift and lifetime of the dispersion oscillator can be obtained from the measured optical parameters.
On the Angular Dependence of Sputtering and Kinetic Electron Emission of Single Crystals
Authors: Martynenko Yu. V.
Published: July 2007

The dependence of the sputtering yield K on the angle of incidence ϕ is calculated for single crystals by taking into account multiple collisions of the ions with atoms of the crystal. The secondary collisions increase the maxima of the curve K(ϕ) but do not alter the form of the minima. The effect of lattice defects on the function K(ϕ) is also considered. These defects mainly alter the minima in K(ϕ) and on the whole decrease the anisotropy of the sputtering yield. Electron emission from single crystals due to ion bombardment is treated in a similar way assuming a kinetic emission mechanism.
Jahn‐Teller Distortions and Inversion Splitting for Transition Metal Complexes and Local Centres in Crystals with Degenerate Electronic T‐terms
Authors: Bersuker I. B. , Vekhter B. G.
Published: July 2007

It is shown that the Jahn‐Teller equivalent configurations of a threefold degenerate electronic T‐term do not seem to correspond to pure tetragonal or pure trigonal distortions as expected from the work of Opik and Pryce [10]. The conclusions of the latter work appear to be valid only to first approximation. The distortions of tetragonal minima under trigonal displacements are obtained. This shows that inversion splitting does occur as predicted earlier [1], in contrary to the statements of Ham [9]. The results of the theory are in agreement with the last experiments by Sturge [8].
Some Kinetic Phenomena in Impure Ionic Semiconductors
Authors: Plâviţu C. N.
Published: July 2007

A criterion is given for finding the regions where one of the various scattering mechanisms is dominant. The phonon drag contribution to some of the kinetic coefficients is only slightly modified when ionized impurity scattering is taken into account.
Comments on Paraelectric Resonance
Authors: Sauer P. , Schirmer O. , Schneider J.
Published: July 2007

The conditions under which paraelectric resonance can be observed are investigated. Paraelectric resonance is defined as a resonant transition between energy levels formed by a site‐degenerate electric dipole in a crystal. Possible applications of the present theory may be found in systems of the type KCl:OH−. In these systems the ground state of the impurity ion has a sixfold site degeneracy which is removed by the tunnel effect and the electric field. Low temperature anomalies of the static dielectric constant caused by the tunnel effect are also discussed.
An Absolute Determination of the Extrinsic and Intrinsic Stacking Fault Energies in AgIn Alloys
Authors: Gallagher P. C. J.
Published: July 2007

Observations have been made of extrinsic‐intrinsic node pairs, and of a hitherto unreported fault pair. It is shown that a simple estimate of the ratio of extrinsic to intrinsic stacking fault energy (γe/γi) cannot be made from the inscribed radii of node pairs, and that earlier qualitative results that γe/γi > 2, or more, are invalid. The simple geometry of the new fault pair facilitates a straight forward absolute determination of both γe and γi. Contrary to published results, γe and γi have been found to be approximately equal. For the present alloys, γe/γi = 1.09 ± 0.1 (for the electron —atom ratio e/a = 1.15) and γe/γi = 1.03 ± 0.1 (for e/a = 1.23). Good absolute agreement has been obtained between γi determined from the fault pairs, and from the observation of extended three‐fold nodes. It is concluded that extrinsic faults are rarely observed because of a high impedance to their formation arising from the co‐operative glide which is necessary, but that, once formed, the extrinsic fault energy is closely the same as the intrinsic.
Colour Centres in X‐Irradiated NaCl:Ag and NaCl:(Ag + Ca) Crystals
Authors: Topa V. , Haragea S.
Published: July 2007

A study is made of colour centres induced by X‐irradiation at room temperature in NaCl:Ag and NaCl:(Ag + Ca). It is shown that the induced bands in NaCl:Ag are strongly dependent on the concentration of Ag as well as on the irradiation time and also that the B‐, C‐, and D‐bands have a complex structure. Three components of the B‐band, four of the C‐band and two of the D‐band are found at liquid nitrogen temperature. Optical bleaching in the F‐light shows that only a component of the B‐, C‐, and D‐bands is definitely electronic. It is also noted that only the optical bleaching of the F‐band in NaCl:Ag results in a simple B‐band much like that obtained by electrolytic colouring. The incorporation of both Ca and Ag in NaCl and subsequent X‐irradiation lead to very intensive B‐ and D‐bands which are shifted to shorter wavelengths compared with those bands in crystals containing only Ag. The optical bleaching experiments on these crystals suggest that colour centres containing both Ca and Ag are probably formed, as in the case of similar crystals electrolytically coloured.
Zur Theorie des Ferromagnetismus magnetisch anisotroper Schichten mit kubischer Kristallstruktur I. Berechnung der Magnetisierung und der Curietemperatur mit der Methode der Greenschen Funktionen
Authors: Brodkorb W.
Published: July 2007

Es wird eine ferromagnetische dünne Schicht betrachtet, deren Atomspins S > 1/2 in einem kubischen Gitter mit (100)‐Oberflächenorientierung angeordnet sind. Der Hamiltonoperator des Systems enthält den Zeeman‐, den Austausch‐ und magnetische Anisotropieterme. Es wird ein expliziter Ausdruck für die Magnetisierung angegeben, und dieser Ausdruck wird dazu benutzt, um die ferromagnetische und paramagnetische Curietemperatur zu berechnen. Dabei wird die Methode der Greenschen Funktionen angewendet.
Direct Measurement of the Diffusion Length of Singulet Excitons in Solid Phenanthrene
Authors: Gillus G. , Wolf H. C.
Published: July 2007

The average radial diffusion length of excitons in evaporated layers of solid phenanthrene is measured directly. Assuming surface‐quenching of the excitons, it is found, that r = 263 ± 85 Å.
Symmetry Orbitals and UV Selection Rules for the Polymethylene Chain
Authors: McCubbin W. L.
Published: July 2007

Basis functions for irreducible representations of the line group of polymethylene chain are presented. This work confirms the general features of a semi‐quantitative band structure given previously. The UV selection rules are derived and are found to support the earlier conjecture that the transition probability for optical transitions to the first unoccupied band is negligible. It is pointed out that the selection rules may also be used to predict the dichroism of the polymethylene crystal.
Structural and Magnetic Properties of Epitaxial Permalloy Films
Authors: Escudier P. , Biragnet F. , Devenyi J. , Yelon A.
Published: July 2007

A study is made of the structural and magnetic properties of (111) films of permalloy (80% Ni, 20% Fe), produced epitaxially (111) Ag on mica. The orientation of the NiFe is parallel to that of the Ag. The anisotropy field is about 2 Oe, and the coercive force is slightly less than this value. The dispersion, α90, is of the order of a degree. The films are largely uniaxial, with a superimposed triaxial component. The presence of a triaxial component is demonstrated by the slow switching properties of the permalloy films, and by their domain structures. It seems that the reversal process, away from the easy axis, is a partial rotation.
Thermally Activated Domain Wall Movement
Authors: Craik D. J. , Wood M. J.
Published: July 2007

Magnetization reversal by slow domain wall motion under constant applied field has been observed by the Faraday effect in permalloy films. A quantitative study (Craik and Wood 1965) of the dependence of wall velocity on temperature and field has been made in the temperature range −47 to +22°C. The linear relationship between the field H and the logarithm of velocity is consistent with previous work, but in addition the variation of the slope of this line with temperature is noted. The analysis of the results is based on Stacey's theory for uniform potential barriers, and an activation volume deduced which is approximately equal to the cube of the film thickness. An estimate is also made of the frequency factor incorporated in the theory, which is consistent with theoretical values. The validity of these calculations is discussed.
Influence of the Perpendicular and Parallel Anisotropy on the Ferromagnetic Properties of Thin Films
Authors: Corciovei A. , Costache G.
Published: July 2007

A calculation is given of the dependence of the spontaneous magnetization in a thin film on the temperature and the number of monoatomic layers in the film. The dependence of Curie temperature on the number of monoatomic layers is also calculated, taking into account the effects of perpendicular and parallel magnetic anisotropy. This work is an extension of a previous theoretical study by Corciovei.
Some Remarks About Electronic Correlation in Crystal Surfaces: The Ideal (100) Surface of a Semi‐Infinite Diamond‐Like Crystal
Authors: Tomášek M.
Published: July 2007

The simple qualitative method for treating electronic correlation in crystal surfaces, suggested recently by the author and by Davison and Amos, is discussed in detail. As an example, a study is made of the effect of interelectronic repulsion on the behaviour of electrons localized near an ideal (100) surface of a diamond‐like crystal. The spin‐degeneracy of the electron surface states is found to be split and possible physical consequences of this splitting are mentioned. Surface states lying in “forbidden” bands differ from volume states in their sensitivity to the magnitude of the volume state energy bands seem to have the same sensitivity to the interelectronic repulsion as the volume states.
Quantum‐Statistical Calculations on the Work Function of Metals
Authors: Dubejko M. , Olszewski S.
Published: July 2007

Work functions of metals with atomic numbers below 40 are calculated using the statistical atomic theory. Good agreement with experiment is obtained for the average value of the work function for each element. For a metallic solid solution with a small heat of mixing the expected work function is rather close to that of the component having the lowest work function and rather insensitive to changes in atomic concentrations.
Zeitabhängigkeit raumladungsbegrenzter Injektionsströme in Fe‐dotiertem p‐Silizium
Authors: Lemke H.
Published: July 2007

Es wird über Impulsmessungen raumladungsbegrenzter Ströme bei p+‐p‐p+‐Kristallen mit eindiffundierten Anreicherungskontakten berichtet. Aus der Zeitabhängigkeit des Injektionsstroms kann die Einfangwahrscheinlichkeit rc (H‐H) bestimmt werden. Bei Vorliegen einer gegenüber der thermischen Löcherkonzentration großen haftenden Raumladungskonzentration erfolgt die Haftstellenentleerung bei stark abgesenkter Löcherkonzentration, wodurch der Retrapping‐Einfluß vernachlässigbar ist. Für die zeitliche Änderung der haftenden Raumladungskonzentration ist das Verhältnis von injizierter getrappter Trägerdichte ΔH+(0) zu der im thermischen Gleichgewicht vorhandenen Zentrenbesetzung H maßgebend. Bei hoher zusätzlicher Besetzungskonzentration erfolgt die Entleerung nach einer Exponentialfunktion, wodurch eine direkte Bestimmung der Emissionswahrscheinlichkeit re ermöglicht wird. Bei kleiner injizierter Trägerdichte ist die zeitliche Anderung der haftenden Raumladung konstant und proportional zu re H. Aus den Emissionswahrscheinlichkeiten erhält man für den Wirkungsquerschnitt (Löcher) des Eisenzentrums g · Θp = 0,7 × 10−15 cm2 (g statistischer Gewichtsfaktor).
A Field Ion Microscope Study of Neutron Irradiated Tungsten
Authors: Attardo M. , Galligan J. M.
Published: July 2007

A study of the damage introduced into tungsten by fast neutrons using field ion microscopy, is described. This consisted of examining the type of damage as reflected in the vacancy content of the material and the removal of the vacancy content after various annealing treatments. Evidence is presented which shows that vacancies are removed from tungsten in stage IV. The observations also indicate the presence of depleted zones in the irradiated tungsten.
On the Mechanism of Sputtering
Authors: Lehmann Chr. , Sigmund P.
Published: July 2007

It is shown that spot patterns in single crystal sputtering do not necessarily arise as a consequence of focused collision sequences. Spots can be obtained if it is assumed that only the surface of a solid has regular structure. The spot width is determined by the energy distribution in the collision cascade and the potential barrier at the surface. The contribution of focusons to sputtering is negligible at low bombarding energies because of the small penetration depth of the ions. Recent experimental results indicate that the average pa thlength offocusons contributing to sputtering is extremely small even at high bombarding energies, so that the proposed sputtering mechanism should be dominant over the whole energy range. This result appears to be consistent with collision cascade theory if forward scattering is taken into account.
Zur Theorie des Ferromagnetismus magnetisch anisotroper Schichten mit kubischer Kristallstruktur II. Berechnung der Curietemperatur für eine Eisenschicht mit (100)‐Oberflächenorientierung
Authors: Brodkorb W. , Haubenreisser W.
Published: July 2007

Für eine Eisen‐(100)‐Schicht werden die ferro‐ und die paramagnetische Curietemperatur als Funktion der Anzahl der Netzebenen berechnet. Es wird ein Vergleich zwischen den Ergebnissen des Molekularfeld‐Modells, der Methode der Greenschen Funktion und experimentellen Daten gegeben.
Determination of the Displacement Vector at the Anti‐Phase Boundaries in Rutile by Contrast Experiments in the Electron Microscope
Authors: van Landuyt J.
Published: July 2007

Contrast experiments are used to determine by transmission electron microscopy and electron diffraction the displacement vector associated with the anti‐phase boundaries in rutile. The criteria derived elsewhere [3] for the contrast at π‐boundaries are applied, and the conditions for extinction of the contrast are also used to determine the vector. A vector of the type 1/6 〈211〉 is found, which is in disagreement with the 1/2 〈101〉 vector previously proposed [1, 2]. The method used here is general and could be used to find the displacement vector at a stacking fault or an anti‐phase boundary in other materials.
Electrical Properties of Anthracene Single Crystals at Very Low Temperatures
Authors: Thoma P. , Vaubel G.
Published: July 2007

The dark current characteristics of anthracene single crystals are measured for a wide range of field strengths up to breakdown at temperatures of 4, 77, and 293 °K. Above the trap‐filled limit the logarithmic current‐voltage characteristic has slopes of the order of 5 to 7. It is shown that this part of the characteristic can be described by a simple expression. The photovoltages under the action of uv excitation are measured and represented analytically. Using a glow‐curve method it is shown that anthracene crystals have quasicontinuous trap distributions for electrons and holes. Because of their lower concentration the distribution of electron traps is observed as a sequence of discrete trap levels.
Properties of Recrystallized Evaporated CdS Layers
Authors: Böer K. W. , Feitknecht J. W. , Kannenberg D. G.
Published: July 2007

Recrystallization of evaporated CdS layers in an environment containing N2, HCl, O2, Cu, and CdS at 630°C are investigated using electron microscopic and electron probe analysis, and show an oxygen enhanced single crystal growth with preferably (001) parallel to the substrate surface. Photoconducting layers of unusual high frequency response for modulated light excitation (35% value at about 100 KHz), low electronic noise (above 60 Hz due to density fluctuation) and high photosensitivity, at 170°K with a maximum gain factor of 108, and a “useful” light/dark current ratio (after 1 s decay) of 107 at 100 ft.‐c are described. These layers have a trap density of ≳ 3 × 1011 eV−1 cm−3 between 0.3 and 0.4 eV and show with 100 ft.‐c bias illumination at room temperature electron lifetime (30 μs) determined relaxation.
Das Ultrarotspektrum von NaNo2 zwischen 30 und 150 μm in der ferro‐ und paraelektrischen Phase
Authors: Vogt H. , Happ H.
Published: July 2007

Die folgende Arbeit befaßt sich mit dem Ultrarotspektrum des Ferroelektrikums NaNO2, dessen Phasenübergang bei 163°C ein Order‐Disorder Übergang ist. Wir haben das Reflexionsspektrum im Bereich der äußeren UR‐aktiven Gitterschwingungen (30 bis 150 μm,) gemessen, und zwar für Polarisationsrichtungen des elektrischen Feldes parallel zu den drei kristallographischen Achsen. In der ferroelektrischen Phase treten fünf Reflexionsbanden auf. Eine von diesen entspricht auf Grund der Gittersymmetrie einer reinen Translationsschwingung der Ionen, während die anderen zu Kombinationen von Translationsbewegungen und Torsionen der NO2−‐Ionen gehören. Bei Erhöhung der Kristalltemperatur von 30 bis 200°C beobachteten wir eine starke Reduktion aller Reflexionsbanden.
Études de la durée de vie et du bruit de génération recombinaison controlés par les dislocations dans le germanium
Authors: Gouskov L. , Lecoy G. , Llinares C. , Savelli M.
Published: July 2007

Une étude du bruit de génération‐recombinaison et de la durée de vie mesurée par décroissance de la photoconductivité est effectuée sur une série d'échantillons des types p et n de germanium dopé en impuretés peu profondes. Les dislocations créées à la naissance du cristal, sont représentées par un niveau accepteur situé environ à 0,15 eV au dessous du bas de la bande de conduction, jouant le rǒle de centre recombinant. La variance des porteurs et les durées de vie mesurées sont, dans le domaine 250°K à 350°K, dues aux processus du type Shockley‐Read de transitions bande à bande, par l'intermédiaire de ces niveaux de dislocations.
Effect of a DC Field on the Lattice Diffusion of Silver‐110 in Copper and Gold
Authors: Archipova N. K. , Klotsman S. M. , Timofeev A. N. , Trakhtenberg I. Sh.
Published: July 2007

A study is made of the effect of a direct current, with a density of about 100 to 150 A/mm2, on the diffusion of silver‐110 in gold (99.99%) and copper (“high purity” grade) at temperatures above 800°C. Diffusion of silver‐110 is measured by the residual activity method. The direction of the electromigration and the magnitude of the activated ion “effective charge” is clear evidence for electron drag. The “effective charge” decreases linearly with temperature increase. The temperature coefficient of the “effective charge” of silver in gold and copper is higher than the temperature coefficient of the matrix conductivity.
Theory of the Photovoltaic Effect in Semiconductors
Authors: Zuev V. A. , Litovchenko V. G.
Published: July 2007

The detailed theory of “surface photovoltage” is developed for the case of small signals in Si and Ge. In addition to the usual factors considered (such as the spreading of space charge during illumination etc.) other important effects such as the trapping of photocarriers on the surface and the photoconductivity in the space charge region are taken into consideration. Δn involves the surface trapping parameters in addition to the electron—hole pair generation rate. A convenient set of approximate equations are chosen, from the usual relations, to describe the dependence of the photo e.m.f. on temperature, surface potential, and the parameters of the local centres. It is shown that under appropriate simplifying assumptions the expressions obtained reduce to those formerly described.
Some Results Concerning the Co++ Site Symmetry in Alkali Halide Crystals
Authors: Musa M.
Published: July 2007

Spectral studies are made of the Co++ ion site symmetry in LiCl and KBr host lattices. It is found that in LiCl and KBr the Co++ ion symmetry is octahedral and tetrahedral respectively. This conclusion is supported by a comparison with CoCl2, Cs3CoCl5, and Cs2CoBr4 spectra. More detailed structures are found in the spectrum of a RbClCo(Zn)Cl2 sample as compared with those exhibited by RbClCo++ single crystals grown from melt.