bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Acceptor States of Hydrogen in Silicon
Authors: Gutsev G. L. , Myakenkaya G. S. 
Published: July 2007

AbstractVarious vacancy complexes are considered in crystalline silicon containing from one to four hydrogen atoms and possessing acceptor levels in the band gap. Their geometrical and electronic structure are calculated by the discrete variational Xα‐method in the cluster approach. It is concluded that for the creation of such acceptor states in the band gap of silicon it is necessary to use some appropriate experimental conditions.
EPR of Lithium‐Induced Silicon‐5dn Pairs in Silicon
Authors: Höhne M. 
Published: July 2007

AbstractA platinum‐analogue to the lithium‐induced silicon‐gold pair, previously investigated, is now detected by EPR. The results underline the close similarity of platinum‐ and gold‐related defects in silicon and suggest a remark concerning the absence of an EPR‐proof of the isolated gold defect, contrary to the platinum defect.
Dependence of Tc on the Hole Concentration in the High‐Tc Superconductors Bi1.5Pb0.5Sr2Ca1−xGdxCu2O8+z
Authors: Kiemel R. , Wischert W. , Kemmler‐Sack S. 
Published: July 2007

AbstractSubstitution of Gd for Ca in the high‐Tc superconductor Bi1.5Pb0.5Sr2Ca1−xGdxCu2O8+z (0 ≦ x ≦ 1.0) is accompanied by a decrease in hole concentration with increasing x. Nevertheless, Tc ≈︁ 90 K remains nearly constant in the interval 0 ≦ x ≦ 0.25. Compounds with x = 0.35 and 0.5 are still superconducting; the increased width of the transition points on a percolation of superconductivity. Compounds with x ≧ 0.75 are semiconductors. The presence of variable range hopping in the insulating regime strongly suggests that the metal—insulator transition is of Anderson type.
Interband Critical Point Parameters Determined by Ellipsometry in CdxHg1−xSe
Authors: Kumazaki K. , Viña L. , Umbach C. , Cardona M. 
Published: July 2007

AbstractThe dielectric function of CdxHg1−xSe crystals, with x = 0 to 0.30, is measured by ellipsometry at room temperature between 1.8 and 5.5 eV. The E1 and E1 + Δ1 gaps and the Δ1 spin—orbit splitting show a upwards quadratic dependence on composition. The broadening of the observed structures increases with x due to alloying effects and disorder or to the difference in chemical activity of the surfaces. The results are discussed in comparison with those obtained for ZnxHg1−xSe and CdxHg1−xTe.
Phonon Localization in Disordered Systems Application of a Probabilistically‐Based Self‐Consistent Theory
Authors: Böttger H. , Theuerkauf M. 
Published: July 2007

AbstractThe probabilistically based self‐consistent theory of localization proposed by Abou‐Chacra et al. and simplified by Logan and Wolynes is extended to phonon localization. For systems with mass disorder, results are derived for the mobility edges and the extent of the localization domain.
A Study for Critical Behaviour of Ferromagnetic Thin Films
Authors: Hai T. , Li Z. Y. 
Published: July 2007

AbstractThe critical behavior of ferromagnetic thin film with two surfaces is investigated by the use of effective field theory with correlations. Surface magnetic order phase is found under certain conditions. The effects of couplings at surface, couplings between surface and nearest neighbouring layer, film thickness, and concentration of magnetic atoms at surface on surface magnetism are discussed.
Mean‐Field Solution of Strongly Correlated Systems Using Hubbard Atomic Operators. Hubbard Model with Infinite U
Authors: Kotrla M. , Drchal V. 
Published: July 2007

AbstractThe hierarchy of equations of motion for double‐time Green functions for Hubbard atomic operators is solved using moment‐conserving decoupling. The lowest order gives a new type of meanfield solution which depends on nonlocal correlation functions. The case of Hubbard model with infinite Coulomb interaction is studied and magnetic properties of the mean‐field solution are investigated employing an additional approximation for correlation functions.
Magnetization Processes of the Rare‐Earth and Fe Sublattices in R2Fe14B (R = Tb, Dy, Ho, Er, and Tm)
Authors: Zhao Tiesong , Fan Zhongzhi , Jin Hanmin 
Published: July 2007

AbstractThe magnetization processes of the rare‐earth and Fe sublattices in R2Fe14B compounds (R = Tb, Dy, Ho, Er, and Tm) along the principal crystal axes at 0 K in fields up to 200 kOe are analysed. The analysis based on the classical three‐sublattice model reproduces fairly well the magnetization processes which are predicted by the analysis based on the crystalline electric field model. The noncollinearity between the magnetic moments of the rare‐earth and Fe sublattices is striking during the magnetization processes, and the Sucksmith‐Thompson method widely used for the evaluation of the magnetocrystalline anisotropy constants cannot be used for the R2Fe14B compound system.
Critical Behaviour of the Magnetic Resonance in KNixMn1−xF3
Authors: Skrzypek D. 
Published: July 2007

AbstractA series of KNixMn1−xF3 (0.3 < x < 0.8) with cubic structure is examined by electron paramagnetic resonance in the region of the magnetic phase transition. The broadening of the linewidth ΔB and the shift of the resonance field Br at a fixed frequency are caused by the onset of magnetic ordering. This work proves Huber's theory that the effects observed near magnetic phase transitions in antiferromagnets depend on the symmetry of the system examined.
Optical Properties and Nature of Coordination of Cu+ Ions in Calcium Metaphosphate Glass
Authors: Debnath R. , Chaudhury J. , Bera S. Chandra 
Published: July 2007

AbstractAbsorption, emission, and excitation spectra of copper(I) ions in calcium metaphosphate glass are investigated. Analysis of the absorption spectrum in the light of ligand field theory reveals that the oxygen coordination surrounding the ion in glass is grossly a trigonally distorted octahedron. A chemical model for the copper(I) ion site in glass is proposed and the mode of distortions that brings about strong trigonal fields at the central ion is discussed. The lowest triplet (3Eg) in the system is identified from emission and lifetime measurements. The observed duality of the triplet emission and its excitation dependence are ascribed to the existence of two relatively predominant slightly different copper(I) sites under the same gross coordination field structure of the glass.
Rearrangement Features of the Vibrational Spectra of TlInS2xSe2(1−x) and TlGaxIn1−xSe2 Solid Solutions
Authors: Sardarly R. M. , Aliev R. A. , Kerimova E. M. , Bakhyshov N. A. , Sadykhov I. Sh. 
Published: July 2007

AbstractTlInS2xSe2(1−x) (0 ≦ x ≦ 0.25) and TlGaxIn1−xSe2 (0 ≦ x ≦ 0.3) solid solutions are studied by the methods of long‐wave infrared (IR) spectroscopy. The domain of existence of an experimentally unobserved tetragonal modification of TlInS2xSe2(1−x) and TlGaxIn1−xSe2 solid solutions at (0.3)0.25 ≦ x ≦ 1 is described and the frequencies of the IR‐active phonons of a tetragonal modification of TlInS2 and TlGaSe2 of A2u and Eu symmetries are determined by a virtual‐crystal approximation in an isodisplacement model without adjustable parameters for intermediate compositions in the case of many oscillators.
The Behaviour of the Hydrogen‐Localized Vibrational Mode in Proton‐Implanted GaAs
Authors: Wang L. P. , Zhang L. Z. , Zhu W. X. , Lu X. T. , Qin G. G. 
Published: July 2007

AbstractA hydrogen‐induced infrared absorption band located around 1835.4 cm−1 is observed in protonimplanted GaAs single crystal at 4.2 K and identified as a hydrogen localized vibrational mode (LVM). The dependence of absorption intensity, linewidth, and frequency of the hydrogen LVM on temperature is presented for the first time. Both, the linewidth and frequency shift due to temperature variation are much larger than those of the hydrogen‐vibration in GaAs observed by Cleriaud et al. A structure model for hydrogen LVM in proton‐implanted GaAs is suggested.
Gapless State in CuFeS2
Authors: Mikhailovskii A. P. , Polubotko A. M. , Prochukhan V. D. , Rud Yu. V. 
Published: July 2007

AbstractA theoretical group analysis of the CuFeS2 structure is made in the presence of magnetic order. It is shown that in such a structure a gapless state may obtained at a point P of the Brillouin zone of chalcopyrite. The existence of ferron states is pointed out. A construction is made of a ferron state corresponding to the specified irreducible representation of the wave vector group of point P of the Brillouin zone. As a result of the analysis the conclusion is made that CuFeS2 refers to gapless magnetic semiconductors where the gapless state is materialized at the boundary of the Brillouin zone and corresponds to a special case of spatial symmetry. In addition, the gapless state appears to be implemented not in usual but in ferron bands. The existence of a ferron hole is predicted. It is pointed out that the gapless state in CuFeS2 corresponds to the first type gapless state according to the character of the temperature dependence of concentration.
Magnetic Susceptibility of an Ising Ferromagnet with Biquadratic Exchange and Uniaxial Anisotropy
Authors: Iwashita T. , Uryǔ N. 
Published: July 2007

AbstractFor the Ising ferromagnets with S = 1, S = 3/2, S = 5/2, the magnetic susceptibility λ is calculated with the use of the pair model approximation. Assuming the bilinear and biquadratic exchange interactions (J and J′) between nearest‐neighbouring pair of spins and the uniaxial single‐ionic anisotropy D‐term for each spin, the behaviours of χ as a function of these exchange parameters and the uniaxial anisotropy parameter are investigated for four cases of the Ising spin system with the above spin values.
Entropy Optimization in Texture Goniometry. II. Practical Applications
Authors: Schaeben H. , Siemes H. , Auerbach S. 
Published: July 2007

AbstractPursuing the approach of finite series expansion methods to the texture problem of recovering an orientation density function (ODF) from its pole density functions (PDF) measured in X‐ray or neutron diffraction experiments, the mathematical model of entropy maximization is applied to pole figure data and numerical results are presented. It is shown that this model as well as its results compare favorably with other methods of ODF restoration because it can yield a solution free of artifacts, also ghosts, if this is at all theoretically possible.
A Study of Manganese Oxides by EXAFS Spectroscopy
Authors: Mande C. , Deshpande A. P. 
Published: July 2007

AbstractThe experimental data of the EXAFS associated with the K absorption discontinuity of manganese are analysed in four manganese oxides, viz. MnO, Mn3O4, Mn2O3 and MnO2 using the graphical method originally proposed by Lytle, Sayers and Stern and recently modified by Deshpande, Sapre and Mande. It is observed that the backscattering parameter β1 decreases nonlinearly with the increase in the O: Mn ratio. A relationship of this kind can be useful in obtaining information about the content of the ligand atoms attached to the metal atom in compounds.
Femtosecond Studies of Transient Nonlinearities in Wide‐Gap II‐VI Semiconductor Compounds
Authors: Rudolph W. , Puls J. , Henneberger F. , Lap D. 
Published: July 2007

AbstractFemtosecond light pulses are a convenient tool to excite and measure various optical nonlinearities with temporal resolution, where today these pulses are available in a broad energy and spectral range. Systematic studies are made of femtosecond transients of wide‐gap II‐VI semiconductor compounds for below‐gap, near exciton‐resonant, and above gap excitation, with pump probe and transient grating techniques. By these means gap‐shrinkage, intraband relaxation and carrier diffusion could be observed with fs resolution. Possibilities are discussed to utilize the nonlinearities for fs pulse shaping and diagnostics.
Absorption and Optical Gain Spectra and Band Gap Renormalization of Highly Excited Quantum Well Systems
Authors: Ell C. , Haug H. 
Published: July 2007

AbstractOptical spectra of highly excited quantum well systems are calculated. Many‐body effects are included within the random phase approximation (RPA). In order to describe a realistic semiconductor quantum well system, finite barrier heights, a thickness‐dependent Coulomb potential and several subbands are taken into account. Furthermore, for quantum well systems like InP/InGaAs or GaAlAs/GaAs, light and heavy hole subbands are included within an effective mass approximation. The renormalization of the band gaps of the allowed transitions are discussed and compared with experimental data of Lach et al. In the range of very high densities deviations between experiment and theory are found, which are probably due to increased intersubband scattering.
Quasi‐Two‐Dimensional Screening of the Electron‐Hole Interaction in Modulation‐Doped Quantum Wells
Authors: Wendler L. , Bechstedt F. , Fiedler M. 
Published: July 2007

AbstractThe screening of the electron‐hole interaction is studied for n‐type modulation‐doped double heterostructures including the effects of size quantization and spatial dispersion accompanying the presence of free carriers. Two different screening models are studied and compared. The resulting screcned potentials are applied to estimate the exciton binding energies by means of a variational procedure. The results are discussed in dependence on the sheet carrier concentration and the well width.
Optical Nonlinearities of GaAs‐Based Epitaxial Structures for All‐Optical Switching
Authors: Oudar J. L. , Sfez B. , Kuszelewicz R. , Michel J. C. , Azoulay R. 
Published: July 2007

AbstractAn experimental study is made of GaAs/AlGaAs monolithic bistable etalons fabricated by metalorganic vapor‐phase epitaxy. Optical bistability is observed in the reflective mode, with a minimum threshold power of less than 3 mW and a switching contrast as high as 30: 1, with a cavity resonator designed to achieve simultaneously a high finesse and a high reflectivity contrast. The dispersive optical nonlinearity of the multiple quantum well active medium is measured as a function of the intracavity intensity, and a strong saturation behavior is observed. The origin of this saturation and its implication on the design of future devices is discussed briefly.
Theoretical and Experimental Results on Coulomb Effects in Semiconductor Quantum Dots
Authors: Hu Y. Z. , Koch S. W. , Lindberg M. , Peyghambarian N. 
Published: July 2007

AbstractRecent theoretical and experimental studies of semiconductor quantum dots are summarized. The one and two electron hole‐pair states are investigated and the effects of quantum confinement and Coulomb interaction are discussed. Besides intrinsic quantum dots, also the effects of trapped carriers and surface polarizations are analyzed. The nonlinear properties are studied by computing the pump‐induced absorption changes (differential transmission spectra). Good agreement with nanosecond and femtosecond hole‐burning experiments is found.
Nonlinearities of CuCl Microcrystals
Authors: Gilliot P. , Hönerlage B. , Levy R. , Grun J. B. 
Published: July 2007

AbstractUsing a “pump and probe” technique, a strong blue shift and a bleaching is measured of the Z3 excitonic absorption line of CuCl microcrystallites embedded in glass. These effects are attributed to exciton exciton‐interactions. They show a response time shorter than the nanosecond. This seems to be mainly due to a fast non‐radiative decay of the excitonic population, leading to a heating‐up of the microcrystals.
Optical Spectroscopy on One‐Dimensional Compound Semiconductor Structures
Authors: Forchel A. , Maile B. E. , Leier H. , Mayer G. , Germann R. 
Published: July 2007

AbstractThe emission of compound semiconductor wires is investigated. Two types of structures are studied. Open wires defined by electron beam lithography and dry etching show a strong reduction of the quantum efficiency due to sidewall recombination if the quantum size range is approached without any indication of lateral quantization. Overgrown etched structures in contrast show a reduced influence of the etched sidewalls on the quantum efficiency and for a lateral width of the order 50 nm indicate the onset of lateral quantization. Buried quantum wires are fabricated by implantation induced disorder. The evaluation of the wire spectra for different widths down to 40 nm indicates the formation of a significant lateral confinement potential in the structures. Using cw and ps spectroscopy carrier capture into the wires and band filling effects are investigated.
Computation of the Structure Factors of the Peculiar Metals Sb, Bi, Ga, and Sn Using Lebowitz's Solution of Hard‐Sphere Mixtures
Authors: Rao R. V. Gopala , Satpathy A. 
Published: July 2007

AbstractThe peculiar metals Bi, Sb, Ga, and Sn, which show a subsidary right‐hand shoulder in the structure factor at or near the melting point, are studied through Lebowitz's solution of hard‐sphere mixtures by assuming the liquids to be a mixture of two types of species of different diameters. The agreement between theoretical and experimental structure factors throughout the whole range of momentum space is excellent. It is found that metalloids like Bi and Sb can be treated as simple hard‐sphere mixtures of two different species while in the case of metals like Ga and Sn a square well attractive tail is used as a perturbation of the hard‐sphere mixture.
Crystal Field and Metamagnetic Behavior of Rare‐Earth Orthoaluminates: DyAlO3
Authors: Kolmakova N. P. , Krynetskii I. B. , Lukina M. M. , Mukhin A. A. 
Published: July 2007

AbstractThe 15 crystal field parameters of a Cs‐symmetry Hamiltonian are determined for the Dy3+ ion in DyAlO3 by fitting the temperature dependences of susceptibility along the three crystal axes, Stark splittings, and the g‐tensor to the values observed. Metamagnetic transitions are investigated for various directions of the field in the ab plane between T = 1.52 and TN = 3.52 K. The metamagnetic behavior of DyAlO3 is in accordance with the character of the Dy3+ ground state, determined by our crystal field data.
Magnetic Properties of Single Crystals of Bismuth Telluride Doped with 0.2 at% Lead and Its Thermoelectric Power
Authors: Biswas S. , Bhattacharya R. 
Published: July 2007

AbstractAt temperatures above 200 K the diamagnetic susceptibility of Bi2 Te3 doped with 0.2 at% Pb decreases with rising temperature which cannot be accounted for by the change in the diamagnetic contribution of the free carriers present in the substance. It is shown that this decrease can be accounted for if χL (diamagnetic contribution of core and valence electrons) decreases with temperature. The thermoelectric power is measured to determine the effective mass of carriers.
Magnetopolaron in a Quantum Well. LO‐Phonon Confinement Effects
Authors: Rücker H. , Mora‐Ramos M. , Comas F. 
Published: July 2007

AbstractMagnetopolarons in a polar‐crystal slab are studied considering electron coupling with confined LO‐Phonons. The electron self‐energy is calculated by using the standard perturbation theory treatment. Screening effects are included within the static Thomas‐Fermi approximation. It is demonstrated that phonon confinement lowers the polaron effects. Special attention is paid to the magnetophonon resonance. Phonon dispersion is shown to be important for the interpretation of the interpretation of the pinning of the transition frequencies for high magnetic fields to values much lower than the Brillouin zone center longitudinal optical phonon frequency ω0.
Optical Properties of Gold in the Nonequilibrium Thermalized Stage
Authors: Wenschuh U. , Heiner E. 
Published: July 2007

AbstractBasing on a recent paper and a linear response theory for highly excited systems far from equilibrium the macroscopic dielectric function (MDF) is evaluated for highly excited noble metal layers by means of the density–density Green's function in RPA with a crude consideration of the band structure of the metal. The evaluation of the time evolution of the directly measurable reflectivity and absorption is added. The results of a model calculation for gold are compared with the results of new time‐resolved pump‐probe‐experiments.
Electric Quadrupole Interaction of 181Ta in Hf2Fe Remeasured
Authors: Akselrod Z. Z. , Komissarova B. A. , Kryukova L. N. , Ryasnyi G. K. , Shpinkova L. G. , Sorokin A. A. 
Published: July 2007

AbstractThe time‐differential perturbed angular correlation (TDPAC) of the 133–482 keV γ‐ray cascade in 181Ta in the intermetallic compound Hf2Fe is measured in the temperature range 78 to 903 K. At 78 K the following parameters of the electric field gradient (EFG) at the two unequivalent Hf sites are obtained: V = (1.91 ± 0.14) × 1022 V/m2, η(1) = 0.505(7); V = (1.05 ± 0.2) × 1021 V/m2, η(2) = 0 (fixed parameter). Discontinuities in the temperature dependence of the EFG parameters at T ≈︁ 600 K are observed as well as an indication at the possible existence of the third Hf site above 600 K.
Theory of Silicon Vacancy in Vitreous Silica
Authors: Dianov E. M. , Sokolov V. O. , Sulimov V. B. 
Published: July 2007

AbstractElectronic properties of a silicon vacancy in solid silicon dioxide are investigated by a semiempirical method, MINDO/3, in a cluster approach. Charge states of the vacancies V, V, V, V, V are considered with taking into account the relaxation of the oxygen atoms of the first co‐ordination sphere of the defects.
Super Hyperfine Structure in the EPR Spectrum of Divalent Manganese in Single Crystal Zinc Selenide
Authors: Marshall S. A. , Yoder‐Short D. R. , Yu C. , Zhang Y. N. , Furdyna J. K. 
Published: July 2007

AbstractThe EPR spectrum of divalent manganese in single crystals of zinc selenide having the zinc blende modification is reinvestigated. In addition to the fine structure and self‐hyperfine structure spectra, the super‐hyperfine structure spectrum due to interactions with host ion nuclei of the first three neighboring shells is observed. A list of spectral parameters deduced from data taken at 4.2 K is given.
Angular Distribution of Elastically Reflected Electrons from Au
Authors: Ding Z.‐J. , Yoshikawa H. , Shimizu R. 
Published: July 2007

AbstractThe angular distributions of elastically reflected electrons from an evaporated gold film surface are measured at primary energies 400, 600, and 800 eV for different angles of incidence between 0° and 75°, and the influence of 2 keV Ar+ ion bombardment is investigated. By means of Monte Carlo simulations the theoretical distributions incorporating multiple scattering are also derived and compared with the experiment. The results reveal that the angular dependency of elastically reflected electrons for polycrystalline Au is dominated by the atomic differential cross sections for elastic scattering.
Tin and Iron Impurity Atom States in Modified As2Se3 Films
Authors: Turaev E. Yu. , Seregin P. P. , Nasredinov F. S. 
Published: July 2007

AbstractElectrical and optical properties of amorphous As2Se3 films modified by tin (a non‐transition metal) and iron (a transition metal) as well as the state of the modifying impurity atoms are investigated. Tin is found electrically inactive in the modified films like in vitreous As2Se3. Iron in the modified films is shown to form donor centers with the ionized and neutral states corresponding to the Fe3+ and Fe2+ ions, respectively. A conclusion is made that an electrical activity of impurities in the chalcogenide semiconductors modified films results from the chemical nature of modifiers whereas the rf co‐sputtering technique provides their high concentration only.