bluuebunny/crossref_metadata_2025_split huggingface dataset:
The absorption spectra of Y3Fe5O12 and Y3Ga5O12:Fe3+ to 5.5 eV
Authors: Scott G. B. , Page J. L. 
Published: July 2007

AbstractThe absorption spectrum of Y3Fe6012 (YIG) is obtained to 40000 cm−1 and analysed by Gaussian fitting to the spectrum of ε0 obtained from the absorption data and the known refractive index behaviour. The energies of the major components agree well with those obtained in Y3Ga5O12:Fe3+. Comparison of the spectra of Y3Fe0.09Ga5.O12 and YIG indicates that all transitions below 35000 cm−1 involve Fe3+ pairs and that the first charge transfer transition between the oxygen 2p band and the iron d‐like bands occurs at 35600 and 37400 cm−1 in YIG and Y3Fe0.09Ga4.91O12 respectively with an oscillator strength of approximately 0.1. An assignment is forwarded for the pair bands in terms of intersublattice Fe3+ charge transfer transitions with reasonable agreement between the expected and observed energies and intensities. An example of the use of the density of states plot, obtained from the analysis, to explain the features of impurity absorption spectra in YIG is given for YIG:Si.
Effect of stress on the raman spectra of Mg2Si and Mg2Sn
Authors: Onaki S. , Cardona M. , Schnherr E. , Stetter W. 
Published: July 2007

AbstractThe effect of uniaxial stress along [100] and [111] on the Raman‐active phonon of Mg2Sn is reported. The effect of a [111] stress on the corresponding phonon of Mg2Si and on the Fröhlichinteraction‐induced LO and 2LO lines of this material is also presented together with complementary measurements of the 2LO line under pure hydrostatic stress. The results are discussed in terms of anharmonic force constants and compared with similar results reported earlier for the F2g phonons of germanium and silicon.
Crystallographic aspects of elastic dispersion in body‐centered cubic transition metals
Authors: Parikh P. , Hay D. R. 
Published: July 2007

AbstractElastic dispersion in the transverse mode in body centered cubic transition metals is described in terms of local lattice dilation and non‐homogenous deformation. The model considers three types of bonding forces. One derives from local lattice dilation with respect to nearest neighbor and next nearest neighbor reference volumes and two derive from angular distortions of the nearest and next nearest neighbors. Elastic dispersion equations are developed and dispersion curves obtained for V, Nb, Ta, Cr, Mo, W, and Fe. Good agreement with experimental data is obtained for these metals except in the region of Kohn and other anomalies and negative dispersion in Nb is interpreted as a result of increasing contribution from local lattice dilatation at higher frequencies.
On the theory of phonon‐modulated electronic transport in off‐diagonal random alloys
Authors: Kolley E. , Kolley W. 
Published: July 2007

AbstractThe theory of the electric conductivity including electron‐phonon interaction is extended to off‐diagonal random alloys. The functional‐derivative technique is used to show the equivalence of the statically approximated tight‐binding model to a generalized stochastic model. Vertex corrections are evaluated by solving Bethe‐Salpeter‐type equations within a modified CPA for the additive limit.
Investigation on the far‐infrared response of DKDP by asymmetric fourier spectroscopy
Authors: Happ H. , Rother G. 
Published: July 2007

AbstractThe complex amplitude reflection coefficient of K(H1−xDx)2PO4, x = 0.86, is measured with E ∥ c and E ⟂ c between 15 and 360 cm1 at room temperature and between 15 and 130 cm−1 at three lower temperatures using an asymmetric Fourier spectrometer. The spectra of both ε′(ω) and ε″(ω) derived thereof are presented. For E ∥ c the ferroelectric mode at room temperature is seen below ω ≈ 30 cm1 and can be described by a Debye formula with ωr = 1/τ  3.12 cm1. For E ⟂ c there is also a low frequency mode due to deuteron motion which can be described by an overdamped oscillator at ω0 = 22 cm1.
Photo and dark conductivity of doped amorphous silicon
Authors: Rehm W. , Fischer R. , Stuke J. , Wagner H. 
Published: July 2007

AbstractThe photo and dark conductivity of boron‐ and phosphorus‐doped amorphous silicon is measured in the temperature range from 100 to 400 K, for various doping levels. Increasing doping generally decreases the activation energy of dark conductivity, down to 0.2 eV, and also decreases the σ0‐value (extrapolation of dark conductivity forT→ ∞). This lowering of σ0is explained by a temperature shift of the Fermi level plus a change in the conduction mechanism. The activation energy of photoconductivity is also lowered, at least by phosphorus doping, which is understood by an influence of doping on the tailing of the bands.
Temperature dependence of the A1 and E optical phonons in BaTiO3
Authors: Scalabrin A. , Chaves A. S. , Shim D. S. , Porto S. P. S. 
Published: July 2007

AbstractMeasurements of all A1 and E transverse and longitudinal phonons in BaTiO3 are reported in the temperature range 10 to 132 °C where the crystal is in the tetragonal phase. A least squares fitting of the spectral shapes is done and the resulting temperature dependence of the frequencies, linewidths and coupling parameters is presented. The temperature dependence of the phonon and electron contribution to the dielectric constant, ε, in the c‐ and α‐axes is determined and compared to the capacitance measurements. It is found that the dielectric constant discrepancy is highly anisotropic.
Residual resistivity of noble metals
Authors: Singh N. , Singh J. , Prakash S. 
Published: July 2007

AbstractThe residual resistivities of noble metals are investigated by alloying 1 at% of monovalent and divalent elements. The form factors due to Singh and Prakash and Moriarty are used for noble metals and the generalized pseudopotential form factors of Veljkovic and Slavic are used for the other elements. The second‐order perturbation theory is applied to include the lattice distortion effects and the results are compared with available experimental values. The agreement is reasonable for some alloys while it is not so for others.
Thermally modulated ultraviolet absorption spectra of CaF:Ce3+ crystals
Authors: Loh E. , Samoggia G. , Reguzzoni E. , Nosenzo L. 
Published: July 2007

AbstractThe thermally modulated absorption spectra (TMA) of Ce3+ in CaF2, crystals at 90 K show the zero‐phonon and vibronics of the 4f → 5d ∣ε〉 transitions. They are more distinctive than that in the conventional absorption spectra. In TMA, the absence of the overlapping background in the composite band between ≈32000 and ≈34000 cm−l enables one to compare the band widths of various orders of vibronics readily and hence to reveal the possible presence of the weak and/or broad 4f → 5d ∣θ〉 absorption at ≈33100 cm−l.
Corrections of the long beating length in quantum modulated electron beams
Authors: Hora H. 
Published: July 2007

AbstractThe quantum mechanical modulation of electron beams crossing a laser beam within a solid, results in an experimental long beating wavelength. The values calculated from a nonrelativistic or from a relativistic theory differ remarkably. A full agreement is reached, if the relativistic dielectric correction of Varshalovich and Dyakonov is included in the relativistic expression for the long beating lengths. The agreement with the Dirac theory is checked and the velocity of the electrons has to be used as given from the relativistic kinetic energy.
Electrical resistivity recovery of cobalt after low‐temperature electron irradiation
Authors: Dander W. , Schaefer H. E. 
Published: July 2007

AbstractAfter electron irradiation at 4.2 K with different doses the annealing behaviour of the electrical resistivity of Co is studied between 15 and 550 K. Two stages at 65 and 300 K show a dose‐dependent temperature shift which may be attributed to the free migration of defects. As the annealing spectrum is found to be rather complex the influence of impurity atoms on the annealing of the radiation‐induced defects cannot be excluded.
Light scattering and spin diffusion in doped semiconductors
Authors: Vasconcellos A. R. , Luzzi R. 
Published: July 2007

AbstractInelastic scattering of light by single‐particle spin‐flip electron excitations and paramagnetic spin‐waves in semiconductor magneto‐plasmas is considered. The generalized Landau quasiparticle picture is used to calculate the Raman cross section. Particular attention is given to n‐doped GaAs for carrier concentrations in the metallic region (rn = 1.6). Scattering of the carriers with lattice vibrations is considered to discuss the spin‐diffusion coefficient, in uniform quasi‐equilibrium conditions, as a function of the magnetic field and the electron effective temperature. Spin‐flip magneto‐Raman investigations in doped semiconductors can produce valuable information on the “hot metallic electron liquid” and its interactions.
Optical properties and plasmon dispersion in epitaxial (SN)x by electron energy loss spectroscopy
Authors: Stolz H. J. , Petri E. , Otto A. 
Published: July 2007

AbstractWavevector dependent electron energy loss spectra of epitaxial films of (SN)x between 0 to 30 eV up to wave vector transfers of 1 Å+1 are measured for k parallel and perpendicular to the chain axis. The optical constants ϵ1, ϵ2 and the reflectivity R are derived by a Kramers‐Kronig analysis for zero wavevector. Peak positions in R agree with optical measurements. A change in the dispersion of the bulk plasmon of the conduction electrons is attributed to the interference with free‐electron‐like single particle excitations.
Formation and properties of the impurity band in n‐ZnSe
Authors: Nedeoglo D. D. 
Published: July 2007

AbstractThe Hall effect, conductivity, mobility, and magnetoresistance of low‐resistivity n‐ZnSe crystals in the temperature range from 4.2 to 300 K are investigated. At room temperature, the electron concentration of the samples investigated is 2 × 1016 to 5 × 1017 cm―3. The maximum electron mobility observed at 60 K is equal to U = 2200 cm2/Vs. Following experimental results are obtained: a maximum on the temperature dependence of Hall cofficient, the negative magneto‐resistance in the helium temperatures range described by Toyozawa's theory and discussed assuming the existence of an impurity band in the samples investigated. A model of the impurity band formation in n‐ZnSe is proposed and its basic parameters are determined.
Lattice dynamics and thermal properties of simple metals based on model pseudopotential calculations
Authors: Prasad B. , Srivastava R. S. 
Published: July 2007

AbstractThe phonon frequencies and Grüneisen parameters are calculated for different values of the phonon wave vector in the three principal symmetry directions for b.c.c. rubidium and cesium using a new form of the local model potential proposed by Krasko and Gurskii. The average values of the Grüneisen parameter γM are also calculated for different temperatures and the results are compared with available experimental and theoretical results.
A simple explanation for the “4kF anomaly” in TTF‐TCNQ
Authors: Phillips J. C. 
Published: July 2007

AbstractIn addition to a Peierls charge density wave with q = 2kF an additional scattering anomaly with q = 4kF is observed by X‐ray scattering. The anomalous temperature dependence of the 4kF anomaly can be explained by impurity ordering stabilized by condensation of Peierls CDW.
Simultaneous Kinetics of Drops and Excitons in Silicon during the Drop Formation
Authors: Collet J. , Barrau J. , Brousseau M. , Maaref H. 
Published: July 2007

AbstractUsing an homogeneous excitation, the simultaneous kinetics of drop and exciton luminescence are measured during the initial regime of drop formation in silicon. Theoretical simulations of the exciton density developped, do not fit well the experimental lineshapes. From an analysis of the experimental curves, it is suggested that a coalescing effect of drops must be taken into account to improve the fit of the experimental kinetics by the theoretical model.
The Critical Voltage Effect in Transmission Electron Microscopy. VIII. The Qualitative Influence of Non‐Systematic Reflections on the Critical Voltage
Authors: David M. , Gevers R. 
Published: July 2007

AbstractThe linear second order critical voltage effect often still occurs when also non‐systematic reflections are excited. However, the critical voltage Vc will in general be different from the purely systematic value V. A simple formula is given to derive a quick estimate for the critical voltage shift, from the structure of the dispersion surface (calculated at V) for the zone considered. This estimate can be useful to guide experiments and exact numerical calculations.
Effective Pair Potential and Thermodynamical Properties of Liquid Gallium
Authors: Badiali J. P. , Defrain A. , Dupont M. , Regnaut C. 
Published: July 2007

AbstractThe thermodynamic properties of liquid gallium are investigated from an effective pair interaction between ions, which explains the properties of the crystalline phases at 0 K for this metal. The results of pseudopotential theory are used and the thermodynamic perturbation method associated with the Gibbs‐Bogoliubov inequality. Computed values agree with the experimental data for volume, compressibility, latent heat, and auto‐diffusion coefficient. Some particularities are predicted of gallium such as low melting point and the fact that the liquid is more compact than the stable crystalline phase.
Phonon Contributions to the Anomalous Specific Heat of Triglycine Sulfate near Tc
Authors: Winterfeldt V. , Schaack G. 
Published: July 2007

AbstractThe ferroelectrics of the triglycine sulfate (TGS) family demonstrate an anomalous contribution to the specific heat near Tc whose peak height can not be accounted for in the usual mean field approximation. It is shown for TGS that this anomaly is due to temperature dependent frequencies of optical phonons near the phase transition temperature.
Influence of Random Electric Fields on the Polarization of Deep Centre Electroabsorption
Authors: Georgobiani A. N. , Ozerov Yu. V. , Strumban E. E. , Vinogradov V. S. 
Published: July 2007

AbstractDeep centres of zinc sulfide single crystals doped with indium to different concentrations are investigated by impurity electroabsorption (IEA) and luminescence. The phenomenon of IEA sign reversal with change of light polarization direction relative to the modulating electric field from the parallel to the perpendicular direction is experimentally observed. An explanation of this effect is proposed assuming a strong EA dependence on the angle between the acting electric field and the light polarization in a crystal with random electric fields.
The Electron‐Two Short‐Wavelength Phonon Scattering in Non‐Polar Semiconductors
Authors: Kubakaddi S. S. , Krishnamurthy B. S. 
Published: July 2007

AbstractThe transport properties are calculated in n‐silicon with the electric field along the 〈111〉 direction, taking into account the electron‐two (short wavelength)‐phonon mechanism besides the usual one‐phonon mechanisms. The variation of warm electron coefficient and zero field mobility with lattice temperature are in good agreement with experimental observations in a wide range of temperature. However, the disagreement noticed in the variation of drift velocity with the electric field in the high field region requires the inclusion of non‐parabolicity of the conduction electrons in the calculation.
Resonant Acceptor Level in Zero‐Gap Semiconductors. Single and Multiple Scattering Effects
Authors: Bastard G. 
Published: July 2007

AbstractA theory of a resonant acceptor level in zero gap semiconductors is developed taking into account the multiple scattering processes. It is shown that the results accounting only for contribution proportional to the impurity concentration describe properly the evolution of the activation energy in Hg1—xCdxTe alloys. However, it is necessary to include the multiple scattering effects to obtain reliable expressions of the density of states and the conductivity. Analytical expressions are obtained and discussed. Comparison with experimental data is made when possible.
Optical and Modulated Absorption Spectra in the Band Gap Region of Amorphous Vanadium Zinc Borate Semiconductors
Authors: Koffyberg F. P. 
Published: July 2007

AbstractThe optical absorption spectra of V2O5—B2O3—ZnO semiconducting glasses, prepared by rf sputtering, indicate that the interband transitions are direct forbidden; for glasses with 50% to 90% V2O5 the optical band gap ranges from 2.51 to 2.31 eV at 100 K. Below the absorption edge the spectra exhibit an Urbach tail. The shapes of the electro‐ and thermomodulation spectra agree qualitatively with theoretical predictions based on the Franz‐Keldysh effect. From a quantitative analysis of the electromodulation spectra in the Urbach tail region a reduced effective mass of 10 mo is derived and band gap values which are 0.2 eV larger than the values obtained from the absorption spectra.
Electron–Phonon Interaction in a Superlattice
Authors: Shmelev G. M. , Chaikovskii I. A. , Pavlovich V. V. , Epshtein E. M. 
Published: July 2007

AbstractThe peculiarities of the phonon spectrum in semiconductors with superlattice are investigated. The dispersion equation is solved for the case of high temperatures: 2Δ ≪ kT (2Δ is the miniband width, T the absolute temperature). The influence of electron‐phonon interaction on the effects under consideration is taken into account.
Moments of Electroabsorption of Jahn‐Teller Impurity Centres
Authors: Perlin Yu. E. , Tsukerblat B. S. , Dod T. Singh 
Published: July 2007

AbstractThe linear and quadratic electroabsorption in the wide electron‐vibrational bands of the cubic centres are studied theoretically on the basis of the matrix formalism of the method of moments. The formulae for the field‐induced changes of the first three moments are derived, and it is shown that the dichroism effect of the electroabsorption allows to determine both the symmetry of the impurity centres and the parameters of Jahn‐Teller interaction.
Dynamic Theory of Conversion Electron Mössbauer Spectroscopy
Authors: Chugunova G. P. , Mitin A. V. 
Published: July 2007

AbstractThe dynamic theory of the conversion electron Mössbauer spectroscopy (CEMS) is considered with the help of the electron–nuclear density matrix. The cross section of the Mössbauer conversion process, electron and conversion linewidths are calculated. As an application of the developed theory, the ultrasonic modulation by Rayleigh waves and the γ‐ray magnetic resonance effect are investigated. The possibility of the CEMS application for surface phenomena is discussed.
A Theory of the Hall Effect in the Hopping Region in Disordered Systems. II. Random Resistor Network and Hall Effect
Authors: Böttger H. , Bryksin V. V. 
Published: July 2007

AbstractLinearizing the rate equation for the diagonal elements of the density matrix with respect to the electrical and magnetic field the basic equations for the Hall effect in the hopping region are derived. The equations hold for ordered as well as for disordered systems. The problem of solving these equations is shown to be equivalent to an investigation of a random resistor network with capacitors and extrinsic currents. For some special cases the Hall mobility is calculated by these equations.
Finite Dislocation Elements in Finite Media. II. Trapezoidal Splitting of Partial Dislocations in Thin Foils
Authors: Korner A. , Karnthaler H. P. , Kirchner H. O. K. 
Published: July 2007

AbstractPartial dislocations in thin foils split trapezoidally. In numerical calculations the presence of the surface and the elastic anisotropy of the medium is taken into account. In Cu–10 at% Al this tendency for nonparallel orientation of the partials is stronger than in silver. The computation is done on the force level by adjusting the geometry of the arrangement till forces and moments are zero. Deviations from isotropic fitting are considerable. The tendency of screw dislocations to cross slip at surfaces is confirmed.
Magneto‐Optical Investigation of the Ground State of the Indirect Free Exciton in Si and Gap
Authors: Donecker J. , Kluge J. 
Published: July 2007

AbstractMeasurements are made of the magnetic circular dichroism (MCD) at the indirect absorption edge of intrinsic Si and GaP at low temperatures and at magnetic fields up to 5 T. By comparison with wavelength modulated spectra it is concluded that the thresholds of the indirect absorption edge for σ+‐ and σ−‐ light are rigidly shifted against each other by the magnetic field. The direction of this shift is connected with the type of assisting phonons. This effect can be explained by the splitting of the 1s ground state of the indirect exciton using group theoretical arguments and can be used to estimate hole g‐values.
A Model for Vacancies in Simple Metals Including an Ionic Potential in the Self‐Consistent Density Calculation
Authors: Perrot F. 
Published: July 2007

AbstractA calculation is made of the vacancy formation energies for Li, Na, K, and Al in the density functional formalism. The difference between the formation energy and the binding energy results from two self‐consistent calculations, one for the perfect lattice with N atoms and one for the defect lattice with N − 1 atoms in the same volume. In both the calculations, the effect of ions is self‐consistently included as a spherically averaged superposition of pseudopotentials. The results improve the “semilinear screening” values due to Evans and Finnis, but remain too large compared with experiment.
Pseudopotential Theory and the Problem of Covalent Bonding. II. Crystals of Si, Ge, and α‐Sn as‐Ordered Systems
Authors: Makhnovetskii A. B. , Krasko G. L. 
Published: July 2007

AbstractA recently developed theory of the covalent bonding using the Brillouin‐ Wigner perturbation series is applied to the analyses of the static stability of Si, Ge, and α‐Sn crystals with diamond lattice. The model proposed considers the latter as an ordered superstructure arising from the b.c.c. disordered solid solution of the element atoms with vacancies. The calculations of lattice stability are performed firstly for pairwise interaction (second order pseudopotential perturbation theory) and secondly for covalency effects. It is the latter that stabilizes the diamond lattice for the three elements. The spatial covalent charge distribution ϱcov(r) is calculated along the [100], [110] and [111] directions and in (110) plane of the b.c.c. lattice. ϱcov(r) is shown to have pronounced maxima just in the points where Phillips' “bonding charges” are localized, but being of a more complicated structure with deep holes in the “empty” sites.
Theory of Two‐Photon Absorption by Surface Polaritons
Authors: Nkoma J. S. 
Published: July 2007

AbstractIt is shown theoretically that observation of surface polaritons by two photon absorption (TPA) is possible. The expression for the TPA coefficient is calculated by using surface polariton response functions, and is found to have a Lorentzian shape. As a result of the TPA, a surface polariton beam grows and its intensity is related to the TPA coefficient. The photon component of the generated surface polariton beam can be detected by a prism‐coupling method. Results applicable to GaP are shown.