bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical and Electrical Properties of of Ruthenium‐Doped TiO2
Authors: Triggs P. , Lévy F. 
Published: July 2007

AbstractOptical absorption spectra and electrical resistivity measurements are given of ruthenium‐doped TiO2. The effect on the system of doping with shallow donors (Ta, Nb) and of reducing in vacuum and in hydrogen is investigated. The results are discussed in view of recent EPR, Mössbauer, and thermogravimetric measurements. Fully oxidised Ru‐doped TiO2 shows an absorption band which is attributed to acceptor transitions of the Ru4+ ion. Absorption bands are observed in reduced and donor‐doped TiO2 which can be assigned to donor transitions of Ru3+ and Ru2+ ions. It is deduced that both treatments lead to reduction of Ru4+ to Ru3+ and Ru2+ before the appearance of free carriers, although differences exist between the effect of doping, of reducing in vacuum, and of reducing in hydrogen. An energy level scheme for the different valence states of Ru in TiO2 is proposed.
Dynamics of Paraelectric and Ferroelectric SbSI
Authors: Rao K. R. , Chaplot S. L. 
Published: July 2007

AbstractThe lattice dynamics of paraelectric and ferroelectric phases of SbSI is studied using a realistic interatomic force model comprising Coulombic and short range interactions, with covalency included between SbS pairs. Characteristic of highly anisotropic systems, the transverse acoustic modes along 〈100〉 and 〈001〉 directions exhibit anisotropy with respect to the TA modes along 〈010〉. This feature explains the nature of diffuse scattering seen earlier in X‐ray measurements. Comparison of optical data made with the results of this study indicates that experimental phonon frequencies and the LO–TO splittings are in reasonable agreement with calculated results. One can refine the calculations by suitable choice of covalent potential parameters and least‐squares‐fitting procedure; however, this has to await further optical and neutron experimental work.
Low‐Frequency Light Scattering in Superionic Glasses (AgI)x (Ag2O1B2O3)1−x
Authors: Fontana A. , Mariotto G. , Rocca F. 
Published: July 2007

AbstractLight scattering measurements are made on superionic glasses (AgI)x(Ag2OnB2O3) 1−x from 2 to 400 cm−1 and in the temperature range 80 to 400 K. The data show the existence of a strong low frequency scattering which has a Lorentzian shape centered at zero frequency. A model is adopted from disordered crystals which treats such scattering as being due to the jumping of Ag ions. The fitting parameters are related to the probability of jump of the diffusing particles in various sites. An order of magnitude calculation relates the quantities obtained by the model with the completely independent measurements of conductivity and tracer diffusion; satisfactory agreement is found.
A MREI Model for Zincblence‐Like Phonons in CdGa2(SxSe1−x)4 Mixed Crystals
Authors: Parisini A. , Lottici P. P. 
Published: July 2007

AbstractResults are given of the Raman scattering measurements on the composition dependence of the optical phonon frequencies in the pseudoternary defect chalcopyrite mixed crystals CdGa2(SxSe1−x)4 over all the composition range. The mode behaviour of all Raman features is tracked and a MREI (modified random element isodisplacement) model to reproduce the concentration dependence of the highest frequency polar zincblende‐like modes is presented.
Soliton Excitations in Terms of Pseudo‐Riemannian Manifolds
Authors: Wiatrowski G. 
Published: July 2007

AbstractAdvantages are shown of description of one‐dimensional ferromagnetic soliton excitations in an anisotropic medium in terms of a pseudo‐Riemannian manifold. The soliton appears then as a solution of a linear equation of motion of the Schrödinger type in an isotropic curved space of observations equipped with a pseudo‐Riemannian metric. Physically this describes, in particular, the temporal fluctuations of the system, and the change of the exchange interactions as well as predicts the superposition of solitons. The approach enables a consistent explanation of the decay of soliton and space deformation as well.
Optical Properties of NiAl Intermetallic Compounds during Concentration and Temperature B.C.C.–F.C.T. Transitions
Authors: Sasovskaya I. I. , Korabel V. P. , Shreder E. I. 
Published: July 2007

AbstractOptical constants in the spectral interval ħω = 0.07 to 4.7 eV are measured to investigate the electronic structure of the b.c.c. β′‐phase (type B2) of NiAl compounds over the entire range of the β′‐phase and especially at the boundary of the β′‐phase, when the latter changes into a lowersymmetry f.c.t. (type LI0) phase. The behaviour of the special features of the optical absorption can be explained, if it is assumed that with the growth of Ni content the Ni d‐band terminates on EF, so that EF is at the small density‐of‐states peak. This is the cause of the structural instability of NiAl compounds in the vicinity of 60 at% Ni. Following the b.c.c.‐f.c.t. martensite transformation the higher‐energy (ħω > 3.5 eV) optical absorption structures due to electron transitions not including EF, are conserved, while the low‐energy structures (ħω < 3.5 eV) disappear and a new absorption band emerges in their place in the infrared region of the spectrum at ≈ 0.8 eV. These changes are analyzed using a Jahn‐Teller type effect model for the suppression of degeneracy of some electron energy bands at EF. Optical data are in agreement with the similar model of peak N (EF) in the b.c.c. phase and N (EF) minimum in the f.c.t. phase, proposed earlier.
A Comparison of the C KVV Auger Spectra of NbC and NbN0.7C0.3
Authors: Shitlga Yu. M. , Gutsev G. L. , Rubtsov V. I. 
Published: July 2007

AbstractThe C KVV Auger spectra of NbC and NbN0.7C0.3 are obtained and compared with each other. It is concluded that essential local redistributions of the electronic density may occur under alloying of NbC and NbN. In particular, the negative charge on carbon atoms in the alloy NbN0.7C0.3 increases as compared to that of NbC.
Theory of Vibrational Relaxation of R 2★ Centres in Rare‐Gas Solids. Application to Ne 2★
Authors: Selg M. 
Published: July 2007

AbstractA tunnel mechanism of vibrational relaxation is proposed for a class of emission centres which are characterized by a weak coupling to the crystalline environment and have vibrational quanta considerably exceeding phonon energies. For such kind of centres, e.g. for R centres in solidified rare gases, a new relaxation channel, connected with the anharmonicity of vibrations, appears. The theory is applied to the centre Ne in solid Ne: a direct calculation of the probabilities of vibrational transitions is carried out.
The Non‐Equilibrium Electron Distribution Function in the Electrical Resistance Problem for Potassium Metal Influence of N‐ and U‐Processes
Authors: Zhernov A. P. , Pashaev Kh. M. , Aliev A. M. 
Published: July 2007

AbstractThe angular and energy structures of the nonequilibrium electron distribution function for potassium at low temperatures are investigated. It is shown that the peculiarities in the δfk structure due to U‐processes are largely suppressed by interference between normal and U‐processes. Hence at the umklapp process freezing temperatures the value of resistivity is affected not only by U‐transitions from “hot spots” but equally by diffuse N‐transitions. The solution of Boltzmann equation by quadrature formulas is discussed.
Cadmium Concentration Dependence of Mobility in Cadmium‐Doped Lead Telluride
Authors: Rustom‐Dalouche R. , Rolland S. , Granger R. , Pelletier C. M. 
Published: July 2007

AbstractLead telluride doped with cadmium is grown in a two temperature furnace. The cadmium content is controlled through cadmium vapor pressure. Electronic concentration and Hall mobility are measured for cadmium concentrations up to 1.65 × 1021 cm−3 at 77 and 300 K. Mobility variations are fairly explained by a model taking into account dispersion on acoustic and optical phonons, and neutral impurities.
Pressure‐Induced Phase Transition in RbH
Authors: Bashkin I. O. , Ponyatovskii E. G. , Dergachev Yu. M. 
Published: July 2007

AbstractMeasurements of the RbH volume in dependence on pressure up to 35 kbar are carried out in the temperature range 290 to 525 K. The bulk modulus of the initial RbH phase is equal to 136 kbar at room temperature. A phase transition with a jump of volume of 8.5% is found in RbH at about 17 kbar. The T–P phase diagram of RbH is plotted. The results obtained are in accord with the previously stated idea of the crystallochemical similarity of alkali hydrides and alkali halides.
Vibrational Modes in Bi12GeO20 and Bi12SiO20 Crystals
Authors: Wojdowski W. 
Published: July 2007

AbstractAn interpretation of the Raman and infrared phonon spectra in Bi12GeO20 and Bi12SiO20 crystals is proposed. Some quasi‐molecular units are distinguished due to the presence of heavy bismuth atoms in the crystal lattice. The frequencies of motion and the force constants of the tetrahedral GeO4 and SiO4 units are determined. Moreover, the frequencies of the stretching modes of A and F symmetry of the BiO bonds are considered and the stretching force constants for the BiO bonds are calculated. The results are in good agreement with the Raman and infrared data obtained in the recent works.
A Parametric Study of Crystal Stability and Surface Energy for Diamond Cubic Structures
Authors: Takai T. , Halicioğ;lu T. , Tiller W. A. 
Published: July 2007

AbstractIn computer simulation calculations, a necessary and sufficient condition for the prediction of relative stability between various crystal structures is a potential energy function that includes a three‐body contribution as well as the usual two‐body contribution. The order of structural stability with increasing three‐body strength parameter, Z*, is h.c.p. → is h.c.p. → f.c.c. → β‐tin → diamond → graphite and structural transformations from diamond → β‐tin and from graphite → diamond are predicted to occur at high pressure. For the diamond structure, marked contraction of the first surface layer spacing is predicted for the (100), (110), and (111) planes with dimer formation on the (100). The reduced surface tension, σ*, decreases with increase of Z* for all three planes and falls in the expected experimental range.
Annihilation of Frenkel Pairs in B.C.C. Metals (α‐Iron). III. The Case of a Hydrostatically Compressed Lattice
Authors: Ratishvili I. G. 
Published: July 2007

AbstractA model describing the Frenkel pair annihilation process in a free b.c.c. lattice is extended to the case of the lattice subjected to external stresses. It is assumed that new conditions of the annealing can be considered in the calculations by a relevant modification of the field of potential barriers dividing the different positions of the Frenkel pair components.
ESR and Optical Absorption Study of the Tl0 (1) Center in NaCl. A Stable Laser‐Active Type Defect
Authors: Nistor S. V. , Heynderickx I. , Goovaerts E. , Bouwen A. , Schoemaker D. 
Published: July 2007

AbstractThe properties are given of the laser‐active type Tl0(l) center in NaCl as derived from an ESR and optical study. The higher thermal and optical stability of this center in NaCl compared to KCl, RbCl, and KBr suggests that it could be a candidate for a viable laser‐active system. The procedure for optimal production of Tl0(l) in NaCl is distinctly different from that known for this center in the other hosts. Optical absorption bands at 470 and 1060 nm, both possessing σ‐character, are attributed to the Tl0(l) center in NaCl and correspond to the so‐called “F‐like” and the pump laser transitions, respectively, of Tl0(l) in the other hosts.
Free Carrier Dynamics and Energy Transfer to the Si Lattice during Pico and Nanosecond Nd Laser Pulse Irradiation
Authors: Baeri P. , Harith M. A. , Russo G. , Rimini E. , Giulietti A. , Vaselli M. 
Published: July 2007

AbstractTransmission experiments of Nd: YAG laser pulse of 25 ps and 30 ns duration through 100 μm thick silicon single crystal allow the determination of the free carrier absorption cross section, σFC = 5 × 10−18 cm2, and of the Auger decay constant, γ3 = 8 × 10−31 cm6 s−1. These two parameters are used in the numerical solution of a set of coupled differential equations which describe the space and time evolution of carrier concentration, carrier energy, and lattice temperature. A comparison with time resolved reflectivity data reported in literature, allows the determination of the energy relaxation time constant, τe ≈︁ 1 ps. The validity of the thermal model used to describe laser annealing in the nanosecond regime is also discussed and justified.
A Model for Band‐Gap Shrinkage in Semiconductors with Application to Silicon
Authors: Landsberg P. T. , Neugroschel A. , Lindholm F. A. , Sah C. T. 
Published: July 2007

AbstractA model for band‐gap shrinkage in semiconductors is developed and applied to silicon. A survey of earlier experiments, and of new ones obtained by the authors, gives agreement between the model and experiments on n‐ and p‐type silicon which is good as far as transport measurements in the ≈︁ 300 K range by various authors are concerned. In fact, the discrepancies between theory and experiment are no worse than the discrepancies between the experimental results of various authors. It also gives a good account of recent optical determinations of the band‐gap shrinkage at 5 K. The model is based on Debye screening and, apart from effective masses, temperature, dielectric constant, and carrier concentrations, which must enter any theory of gap shrinkage in some form, it is parameter‐free. The model gives in Gaussian units ΔEg =126,6(m*/m)1/2 ×(ϵ/10)−3/2(n/1018)1/6 meV in the degenerate limit.
New Experimental Evidence Concerning the Nature of L, M, and N Lines in ZnSe:Co
Authors: Sokolov V. I. , Surkova T. P. , Kulakov M. P. , Fadeev A. V. 
Published: July 2007

AbstractThe absorption and electroabsorption spectra of ZnSe:Co in the region of the L, M, and N lines are investigated. The experimental data indicate that these lines arise from transitions to excited states of d7 configuration. The electroabsorption spectrum exhibits new α°, β°, γ°, δ°, and ϵ° lines that have intense LO phonon replicas. These lines result from the formation of donor excitons according to the scheme d7 + hω → [d6e]. The d7 configuration ground state 4A2 is separated from the bottom of the conduction band by 2.565 eV assuming a hydrogen‐like electron binding energy.
Direct Observation of Bound Excitons in the Spectra of Resonance Secondary Emission of LiH:Mg Crystals
Authors: Pilipenko G. I. , Plekhanov V. G. , Tyutyunnik V. I. , Tyutyunnik O. I. , Gavrilov F. F. 
Published: July 2007

AbstractAn experimental study is made of resonant secondary emission, reflection, and excitation spectra which indicate the existence of bound excitons in LiHMg crystals. The spectroscopic properties of the bound exciton are studied by selectively excited luminescence and resonant Raman scattering. The resonance energy of the bound exciton is estimated to be 4.842 eV. For the first time, the transformation of resonant Raman scattering into luminescence is found when the incident photon energy is above the resonance.
ESR of Isolated Mn2+ Centers in Alkali Chlorides
Authors: De Keersgieter A. , Callens F. , Baroen M. , Matthys P. , Boesman E. 
Published: July 2007

AbstractThe ESR spectra of isolated Mn2+ centers in NaCl and KCl single crystals, formed by a high uniaxial stress, are observed at room temperature. The formation mechanism of these impurity centers with cubic symmetry is discussed. From the analysis of the spectra it is concluded that these Mn2+ centers are identical with centers, formed by heating unstressed NaCl:Mn2+ and KCl:Mn2+. Similarities and differences with uniaxially stressed alkali chlorides, doped with V2+ ions, are also analysed.
Site Selective Spectroscopy of ZnS:Tm3+ Crystals
Authors: Zimmermann H. , Boyn R. 
Published: July 2007

AbstractThe method of site selective excitation spectroscopy is applied to Tm3+ ions in ZnS crystals containing various codopants. By dye‐laser 4f–4f excitation at helium and neon temperatures it is possible to separate three different sites, for which 4f–4f emission, excitation, and absorption spectra are determined in the range of several free‐ion transitions. Energy spectra are deduced from these data, and some considerations are made about the nature of the sites observed.
MNDO Calculation on Molecular Clusters Chosen to Model the Bonding of Oxygen in Silicon
Authors: Ying Xie , Snyder L. , Sahu S. N. , Corbett J. W. 
Published: July 2007

AbstractMNDO (Modified Neglect of Diatomic Overlap) method cluster computations are carried out in studies of the bonding state and behavior of oxygen in a silicon lattice. These studies are compared with similar ab‐initio work. The MNDO studies find the most stable bonding state for oxygen to be a pyramidal ylid structure. The mixing of 3s with 3p orbitals in the lone pair of the trivalent silicon in the pyramidal ylid is believed to stabilize this structure. This point remains to be explored in ab‐initio computations where C2v symmetry is assumed. Since these MNDO calculations find the observed puckered bond‐centered interstitial oxygen configuration to be less stable than the pyramidal ylid structure, it is concluded that the present MNDO parameters may not be optimum for silicon.
Pairs of F‐Centres and F− Impurities in KCl Studied by ENDOR
Authors: Söthe H. , Studzinski P. , Spaeth J.‐M. 
Published: July 2007

AbstractBy optical bleaching of F‐centres in KCl doped with KF at −60 °C about half of the F‐centres can be converted into room temperature stable pairs of F‐centres and F− impurity ions, which have a single optical absorption band peaking at a 5% lower energy than the F‐centre. With electron nuclear double resonance (ENDOR) could be shown that the F− impurity resides in a [200] next‐nearest position and not in a [110] nearest halogen position. The K+ ion between the anion vacancy and the F− ion is displaced by ≈︁ 11% towards F−. Its superhyperfine constants show a strong temperature dependence.
Electron–Electron Interaction and Isotope Effects in Superconducting Metal–Hydrogen (Deuterium) Systems Like PdHx(Dx)
Authors: Drechsler S.‐L. , Zhernov A. P. 
Published: July 2007

AbstractUsing various experimental and theoretical data the origin of the inverse isotope effect (IIE) for the superconducting transition temperature Tc of the PdH(D) system is analyzed on the basis of a solution of the Berk‐Schrieffer equations. It is found that the IIE can be described at weak or intermediate anharmonicity of the electron–optical phonon interaction β = (λ/ −1≈︁to 0.14, standard or slightly enhanced values of Coulomb pseudopotential μ', and weak spin fluctuations λsp ≈︁ 0.05 to 0.1. The importance of the electron‐electron interaction in determining the superconducting properties of non‐stoichiometric PdHx(Dx) and some other hydrides (deuterides) is emphasized.
Phonon Structure (α2F(Ω)) of Superconducting V3Si Monocrystals by Tunneling Measurements
Authors: Schumann J. , Otschik P. 
Published: July 2007

AbstractOn the surface of single phase V3Si single crystals, tunnel junctions with different superconducting electrodes are prepared, which have reproducible and stable characteristics. In the second derivative of the (U)‐characteristics well defined extrema in the energy range of phonon excitations 15 meV ≦ E ≦ 50 meV may be detected. The general capability of the tunnel element on V3Si for phonon investigations is proved by the detection of phonon structures of the Pb and In top electrodes. By detailed investigations in the temperature range of T ≦ Tc (V3Si) and T ≦ Tc (V3Si) it is verified, that the structures found in tunnel characteristics are caused by phonon induced effects in V3Si. The solution of the Eliashberg equation, obtained by means of experimental tunneling data, yielded for the electron‐phonon coupling constant λ = 2 ∫ α2(Ω) F(Ω) dΩ/Ω ≈ 1. This allows the conclusion to classify V3Si as a superconductor with strong electron‐phonon interaction.
161Dy Mössbauer Effect in Dy2Fe14B
Authors: Gubbens P. C. M. , Van Der Kraan A. M. , Buschow K. H. J. 
Published: July 2007

AbstractThe 161Dy Mössbauer effect is measured in the tetragonal compound Dy2Fe14B at various temperatures between 4.2 and 300 K. The spectra are analysed in terms of two subspectra associated with the two crystallographic Dy sites in the structure of Dy2Fe14B. It is found that the crystal field split ground state corresponds to Jz = −15/2 for both the types of sites. The results of bulk magnetization measurements and the temperature variation of hyperfine field and quadrupole splitting are used to derive values of the magnetic coupling constant between the Fe moments (JFeFe) and the rare earth and iron moments (JFeR).
Wannier‐Mott Exciton States in Two‐Layer Periodic Structures
Authors: Pokatilov E. P. , Beril S. I. , Fomin V. M. , Pogorilko G. A. 
Published: July 2007

AbstractA theoretical research of Wannier‐Mott exciton states in two‐layers periodic structures is carried out. The potentials of the electron‐hole interaction and the self‐action are found on the basis of exact solution of the Poisson equation with account of the anisotropy of dielectric constants of these structures. It is shown that the self‐action effect influences essentially the exciton energy spectra, leading to the renormalization of the energy band gap. Analytical results are obtained for the limiting case of thin‐layer period structures.
Planar Channeling Radiation of Positrons and Electrons at Moderate Energies in Simple Crystals
Authors: Dedkov G. V. , Shidov E. Kh. 
Published: July 2007

AbstractA theoretical calculation of the positron and electron Kumakhov radiation peak energies at planar channeling in simple crystals (diamond, silicon, and germanium) is made. The particle energies are in the range 28 to 56 MeV. The calculation is based on a potential model, proposed earlier. A detailed comparison with experiments and other theoretical models is given.
Optically Detected Cyclotron Resonance in AgBr
Authors: Booth I. J. , Schwerdtfeger C. F. 
Published: July 2007

AbstractOptically detected magnetic resonance (ODMR) studies reveal cyclotron resonance of electrons and holes in AgBr as well as a number of paramagnetic resonances already observed by other workers. Cyclotron resonance signals are observed in the recombination radiation from excitons bound to iodine isoelectronic impurities. Asymmetry of the electron‐cyclotron resonance gives a measure of the nonparabolicity of the conduction band which results in an energy dependent effective mass. The enhanced trapping of electrons on iodine centres by interaction with LO phonons is discussed.
Order Parameter Functional Method in the Theory of Atomic Ordering
Authors: Gusev A. I. , Rempel A. A. 
Published: July 2007

AbstractAn order parameter functional method is proposed which permits the description of structural order‐disorder‐type phase transitions and combines features of the cluster variation method and static concentration waves method. The method proposed is employed to describe the atomic ordering in a nonstoichiometric niobium carbide.
Semiclassical Theory of Dechanneling and the Diffusion Coefficients
Authors: Nitta H. 
Published: July 2007

AbstractA new expression of the “local diffusion coefficient” for dechanneling theory is derived within a framework of the semiclassical approximation. By making use of the present result, the diffusion coefficient for nuclear contribution is calculated in detail. It is shown that the nuclear diffusion coefficient can be approximately represented in the form Dn=DK‐o+DL where Dk‐o and DL are the Kitagawa‐Ohtsuki's formula and the Lindhard's formula, respectively. These conclusions correspond to Matsunami‐Howe's proposal and Fuschini‐Uguzzoni's computer simulation.