bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic Properties of the Three‐Dimensional Ising Model with an Interface Amorphization
Authors: Benyoussef A. , Amraoui Y. El , Kenz A. El , Saber M. 
Published: July 2007

AbstractA three‐dimensional ferromagnetic Ising model with an interface amorphization is investigated with the use of the effective field theory. Phase diagrams and reduced magnetization curves of interface and bulks are studied. We obtain a number of characteristic behaviours such as the possibility of reentrant phenomena and a large depression of interface magnetization.
Pyroelectric Effect, Optical Birefringence, and Non‐Linear Dielectric Constant in Betaine Arsenate
Authors: Lacèrda‐Aroso M. T. , Ribeiro J. L. , Chaves M. R. , Almeida A. , Vieira L. G. , Klöpperpieper A. , Albers J. 
Published: July 2007

AbstractDetailed measurements of the pyroelectric coefficient and optical birefringence in betaine arsenate, in a temperature range centred at the ferroelectric phase transition (Tc2 ≈ 121 K) are reported. The critical behaviour of the spontaneous polarization is analyzed from these data and a cross‐over between two different critical regimes is evidenced. Results of linear and non‐linear dielectric constant measured along [001] are also reported.
Localization Properties of 1D Disordered Systems in the Presence of An Electric Field
Authors: Brezini A. , Sebbani M. , Depollier C. 
Published: July 2007

AbstractA Kronig‐Penney model with a constant electric field is used to examine the transmission properties of electrons in one‐dimensional disordered systems. Disorder is introduced into the system by assuming that the strengths of the δ‐function potential are random variables uniformly distributed. In particular the cases where the strength varies from 0 to W (barriers) and from −W to 0 (wells) are considered. Extensive results are presented and compared to other theories.
Hydrogen Chemisorption on Supported Semiconductor Films
Authors: Sun Qiang , Xie Jianjun , Zhang Tag 
Published: July 2007

AbstractHydrogen chemisorption on metal supported semiconductor ZnO films is studied by using the Green function method and complex‐energy‐plane integration approach. The Anderson‐Newns model is used to calculate the chemisorption energy ΔE and the adatom charge transfer Δq. The variations of the adatom state level Ead and the corresponding localized adatom density of states (LDOS) with increasing ZnO film thickness are investigated. It is found that the hydrogen chemisorption energy and the adatom charge transfer depend on both the thickness of the ZnO film and the species of the metal support. The calculations show that ten layers of ZnO film can mirror the chemisorption properties of bulk ZnO. The adatom state level Ead which corresponds to a peak in Ldos, is found shifting upwards to a constant value as the ZnO layer number N increases from 1 to 10.
Pressure Dependent Properties of Boron Phosphide
Authors: Badi N. , Amrane N. , Abid H. , Driz M. , Soudini B. , Khelifa B. , Aourag H. 
Published: July 2007

AbstractAn adjusted local pseudopotential method is used to obtain the electronic band structure of boron phosphide under pressure. The electronic charge density distributions are computed at several points of the valence and conduction band edges. These charge densities are used to study the modification of the bonding and electronic properties of the compound with respect to different volumes ranging from 0.75 V0 to V0.
EPR Study of Low Symmetry Mn2+ Centers in LiNbO3. Superposition Model and Crystal Field Analysis of the Zero‐Field Splitting Parameters
Authors: Yeom T. H. , Choh S. H. , Chang Y. M. , Rudowicz C. 
Published: July 2007

AbstractX‐band EPR spectra of Mn2+ : LiNbO3 single crystals at room temperature are analyzed with a spin‐Hamiltonian of C3 symmetry. Experimental data are interpreted using the superposition model in a twofold way. Firstly, the zero‐field splitting (ZFS) parameters b, b, b and b4−3 are predicted. While the results for b are not conclusive, those for the major fourth‐order ZFS term |v| = [(b)2 + (b4−3)2]1/2 indicate better agreement with experiment, assuming Mn2+ at the Nb site. Secondly, crystal field (CF) parameters are obtained from the superposition model using two sets of available structural data. Diagonalization of the CF Hamiltonian within the whole 3d5 configuration yields the theoretical ZF splittings. The results for Mn2+ at the Nb site agree better with the experimental data than those for Mn2+ at the Li site. Hence the superposition model analyses of the observed EPR spectra indicate that the spectra can be most likely attributed to Mn2+ ions at Nb sites. The ways to reconcile this conclusion with the opposite one from the low temperature ENDOR study are discussed.
Magnetoresistance and Hall Effect of Ferromagnetic Amorphous Alloys (Fe100‐xMnx)75P15C10
Authors: Bärner K. , Heinemann K. , Medvedeva I. V. 
Published: July 2007

AbstractThe Hall effect ϱH and the magnetoresistance Δϱ/ϱ of ferromagnetic amorphous ribbons of (Fe100−xMnx)75P15C10 are measured for 0 ≦ x ≦ 30, 77 K < T < 300 K, 0 < B0 < 0.4 T, and 0 < p < 2 × 108 Pa. Both transport properties are determined by the number and distribution of spin scattering centers, some of which can be reoriented in external magnetic fields.
Electron Transport in Vapor Deposited Molecular Glasses
Authors: Borsenberger P. M. , Detty M. R. , Magin E. H. 
Published: July 2007

AbstractElectron mobilities are measured in a series of vapor deposited l,‐l‐dioxo‐4‐(dicyanomethylidene)thiopyran glasses. The results are described within the framework of a formalism based on disorder, due to Bässler and coworkers. The formalism is based on the assumption that charge transport occurs by hopping through a manifold of localized states with superimposed energetic and positional disorder. The key parameters of the formalism are σ, the energy width of the hopping site manifold, μ0, a prefactor mobility, and Σ, a parameter that describes the degree of positional disorder. Experimental values of σ are approximately 0.123 eV for all compounds. The width of the hopping site manifold can be described by arguments based on dipolar disorder, if it is assumed that the hopping site energies are determined by group dipole moments associated with the cyano and sulfone functionalities. The prefactor mobilities are between 1 and 4 × 10 −2 cm2/Vs. A comparison of these results with literature values for molecular glasses suggests that the prefactor mobilities may be dependent upon the dipole moment. Values of the positional disorder parameter Σ are approximately 2.0 and attributed to packing constraints.
Analysis of Hydrogen in Aerosol Particles of a‐Si: H Forming during the Pyrolysis of Silane
Authors: Onischuk A. A. , Strunin V. P. , Ushakova M. A. , Panfilov V. N. 
Published: July 2007

AbstractThe hydrogen content in aerosol particles of a‐Si: H, forming during pyrolysis of silane, is studied by means of the methods of hydrogen evolution and IR spectroscopy. The conclusion is drawn that the evolution peaks at 650,730, and 750 to 850 K correspond to hydrogen present in the dihydride groups of polysilane chains, the monohydride groups of the clustered phase, and the monohydride groups of the dilute phase, respectively. In the IR spectra the monohydride groups of the clustered phase cause absorption near 2000 cm‐−1 and the monohydride groups of the dilute phase near 2100 cm‐−1. Under low silane conversion the main fraction of hydrogen is contained in (SiH2)n, under conversion more than 50% in monohydride groups.
Laser‐Induced Coloration and Discoloration Processes in Alkali Halides
Authors: Bichevin V. , Käämbre H. 
Published: July 2007

AbstractThe coloration kinetics of KCI, KBr, KI, and NaCl crystals under XeCl excimer laser irradiation (hv = 4.02 eV) at room temperature as well as laser‐induced discoloration of preliminarily X‐ray coloured crystals, including samples with M and R centres are studied. It can be concluded from the results that the achieved colour centre concentrations are determined by a dynamical equilibrium between laser two‐quantum coloration and a concomitant one‐quantum bleaching of the created centres. Most probably the bleaching proceeds via the laser‐light‐induced destruction of the F centre complementaries, V centres and annihilation of some produced mobile products (H interstitials?) with F centres. The X‐ray‐created F centres seem to bleach more rapidly than the laser‐created ones.
Solid Solubility of Cu in Al under Pressure and Elastic Moduli
Authors: Soma T. , Ishizuka M. , Kagaya H.‐Matsuo 
Published: July 2007

AbstractThe solid solubility of Cu in Al under pressure is studied using the microscopic electronic theory. An increase of the solubility up to 10 at% Cu in Al is predicted under a pressure of 10 GPa. The obtained results for the lattice constant, the heat of solution, the pressure‐volume relation, and elastic moduli in the Al‐Cu system are presented theoretically.
Electronic Properties of Quasi‐One‐Dimensional Chains at Zero Temperature and T ≠ 0 K
Authors: Schulte J. , Böhm M. C. 
Published: July 2007

AbstractThe electronic properties of quasi‐one‐dimensional (1D) organic/organomctallic chains in the metallic phase are discussed in the theoretical framework of an analytic many‐body description. The dynamics of the charge and spin degrees of freedom are quantified by the respective mean‐square deviations (i.e. fluctuations). The conditions leading to a simultaneous and nonsimultaneous occurrence of charge and spin fluctuations are discussed. By means of the electronic charge fluctuations the probabilities Pi(n) to find n = 0, 1, 2 electrons at the i‐th lattice site are calculated. These elements are input parameters for the determination of the magnetic susceptibility, Knight shift, and electronic effective mass in the correlated ground state at T = 0 K and T ≠ 0 K. The material parameters are enhanced due to many‐particle interactions.
Semiconducting Properties of Hexagonal Chromium, Molybdenum, and Tungsten Disilicides
Authors: Filonov A. B. , Tralle I. E. , Dorozhkin N. N. , Migas D. B. , Shaposhnikov V. L. , Petrov G. V. , Anishchik V. M. , Borisenko V. E. 
Published: July 2007

AbstractSelf‐consistent electronic property simulation of hexagonal CrSi2, MoSi2, and WSi2 is performed within the local density approximation using the semirelativistic linear muffin‐tin orbital method. They are deduced to be narrow‐gap semiconductors with indirect band gaps of 0.29,0.07, and 0.07 eV, respectively. The effective masses of holes and electrons in the disilicides are of the same order. They are close to the free electron mass in CrSi2 and there is a certain reduction of the appropriate values from chromium to tungsten disilicides. Carrier mobility calculations show that the scattering on acoustic phonons is dominant for the disilicides. The hole mobilities at 300 K are 42, 190, and 209 cm2/V s for CrSi2, MoSi2, and WSi2, respectively.
Application of Lattice Inversion Method to Embedded‐Atom Method
Authors: Xie Qian , Huang Meichun 
Published: July 2007

AbstractA model for the embedded‐atom method with the use of the lattice inversion method is presented. The lattice sums of electron density and pair potential are assumed to be exponential functions of the lattice parameter. The individual functions of potential and density are inverted from the corresponding lattice sums by using the lattice inversion method. The model parameters are explicitly written by five physical inputs, i.e. the equilibrium lattice constant, the bulk modulus, the Voigt average shear modulus, the sublimation energy, and the unrelaxed vacancy‐formation energy. As applications, the 〈100〉 uniaxial stress strain curves in the absence of lateral contraction and shear‐mode failure for Cu, Ag, Au, Ni, Pd, and Pt are calculated. The predictions of tensile strengths and failure strains by the present method are found smaller than those by the pair‐potential model. The results are in agreement with first‐principles calculation of Esposito et al. for Cu and with empirical calculations of Milstein for Ni.
Density of States of Disordered Coupled Peierls Chains
Authors: Mertsching J. 
Published: July 2007

AbstractThe electron density of states of coupled bond‐disordered Peierls chains is approximately calculated in two and three dimensions, regarding nearest‐neighbour chains to be independently disordered. Both the bond disorder due to lattice fluctuations and the chain coupling contribute to the tail states within the one‐dimensional gap. The results are discussed for trans‐polyacetylene.
MFRG‐DPIR Study of the Ising Model: Spin‐3/2 with Random and Spin‐5/2 with Fixed Transverse Field
Authors: Song W. J. , Yanc C. Z. 
Published: July 2007

AbstractThe phase diagram and other critical properties of the Ising model of spin‐3/2 in a random transverse field (RTIM) and spin‐5/2 in a transverse field (TIM) are investigated within the approximate scheme which is combined by mean‐field renormalization group theory (MFRG) with the discretized pathintegral representation (DPIR).
Thermoluminescence and Phosphorescence of VUV‐ and X‐Irradiated CaO Monocrystals at Low Temperatures
Authors: Dolgov S. A. , Kärner T. , Maaroos A. , Savikiiina T. I. , Vasilchenko E. A. 
Published: July 2007

AbstractThermoluminescence (TL) of CaO and CaO‐Bi monocrystals VUV‐irradiated at 80 K or X‐irradiated at 4.2 K is reported. Varying the energy of VUV‐irradiation, the TL creation spectra (TLCS) of various peaks are derived. From the analysis of these spectra it is concluded that in the excitation spectrum of CaO indirect transitions may play an important role already from Eexc = 6.5 eV. Long‐lived phosphorescence, as well as low‐temperature TL peaks at 20, 37, and ≈ 50 K of X‐irradiated CaO and CaO‐Bi monocrystals at LHeT are observed. The observed phosphorescence is interpreted as a tunneling recombination between holes and electrons, trapped, respectively, by cation vacancies (V centers) and unidentified donor centers, thermal destruction of which takes place at ≈50 K.
Ionization of Interstitial Iron Atoms in β‐Rhombohedral Boron
Authors: Kuhlmann U. , Werheit H. , Pelloth J. , Keune W. , Lundström T. 
Published: July 2007

AbstractMössbauer spectra of β‐rhombohedral boron with interstitially distributed iron atoms up to 3.33 at% are presented. Taking into account that the six D sites in the unit cell are saturated by two Fe atoms, the distribution of the Fe atoms on A and D sites proved to be simply statistical. At lower Fe contents single iron atoms on A sites are ionized to Fe3+, while towards higher Fe contents a rapidly increasing share of Fe2+ ions is found. On D sites the ionization of single Fe atoms is 2+, but it changes to 3+, when two Fe atoms are accommodated in the D sites of one unit cell. The isomer shift of the Mössbauer doublets yields an estimation of the electron transfer to the boron framework. Transition from p‐ to n‐type takes place, when six electrons per unit cell are transferred from the iron ions to the boron framework. This number corresponds to the sum of the unoccupied sites in the upper valence band and the possible electron traps generated by an electron–phonon interaction in the B12 icosahedra.
Infrared Vibrational Modes and Anisotropy of the Effective Ionic Charge in CuAlSe2, CuAlS2, and CuGaSe2 Crystals
Authors: Andriesh A. M. , Syrbu N. N. , Iovu M. S. , Tazlavan V. E. 
Published: July 2007

AbstractReflectivity spectra of CuAlS2, CuAlSe2, and CuGaSe2 crystals have been investigated in the wave number range 50 to 600 cm−1 for the polarizations E ‖ c and E ⊥ c. The fundamental phonon parameters, the limiting dielectric constants ε∞ and εS and the reflectivity spectra contours have been calculated by using classical dispersion relations for both E ‖ c and E ‖ c configurations. The Szigeti effective charges and the relative ion charges of Cu, Al, Ga, Se, S anions and cations have been calculated in dependence on the incident light polarization.
A New Approach to the Correlation of the Electrical Properties with Interband and Intraband Transitions of Thin Cr Films
Authors: Fouad S. S. , Ammar A. H. , El‐Fazary M. H. 
Published: July 2007

AbstractThin chromium films of thickness ranging from 25 to 80 nm are prepared by thermal evaporation under a vacuum of 1.33 × 10−3 Pa. The electrical resistivity was inversely proportional to the thickness of the film. The analysis of the electrical resistivity is treated in the frame of the effective mean free path theory of size effect developed by Pichard et al. Such analysis allows the determination of the mean free path l0, carrier concentration nc, relaxation time τ, and Fermi energy EF. The optical constants, n and k, of chromium thin films are determined in the spectral range of 200 to 25000 nm. The obtained results agree with the optical conductivities predicted theoretically by Moruzzi et al. In addition, the values of nc, σs, l0, and τ obtained electrically are found to match with those obtained optically.
Damping of Surface Plasmon–Phonon Polaritons
Authors: Barlas T. R. , Dmitruk N. L. 
Published: July 2007

AbstractThe influence of the bulk damping in polar crystals on the elementary properties of surface polaritons (SP) of a mixed plasmon–phonon type is studied theoretically. Two different methods for the calculation of SP damping are used. These methods are shown to give the same results. Definite combinations of the plasmon and phonon damping constants are found to lead to a minimum in the damping and a maximum in the planar propagation length versus wave vector dependences. An increase in the SP energy dissipation due to an increase in the damping constants of elementary excitations in a crystal and the SP scattering by surface roughness give rise to a reduction of the SP frequency, but the shape of the dispersion curve changes differently, what can be distinguished experimentally.
Electronic Transport through Silicon (a‐Si:H) Barriers in Hydrogenated Amorphous Germanium (a‐Ge:H)
Authors: Drüsedau Thilo P. 
Published: July 2007

AbstractFilms of a‐Ge:H containing single and double barriers of a‐Si:H with a total thickness of 10 nm are prepared by rf PCVD from germane and silane, respectively. The current–voltage characteristics of the sandwich structures are smooth and do not show any irregularities. The differential conductivity σ(E) of the structures is nearly step‐like with values of 3 × 10−8 and 10−5 ω−1 cm−1 for external fields below 200 and above 1000 V/cm, respectively. The ohmic conductivity (at lower fields) of the ultrathin a‐Si:H barriers is identical to bulk a‐Si:H and is 10−10 Ω−1 cm−1. This implies a discontinuity of the conduction band edge at the a‐Si:H/a‐Ge:H interface of 0.3 eV. For low fields and below 240 K, there is ohmic hopping with an activation energy of 0.3 eV. The internal field in the barrier reaches very large values of 4 × 105 V/cm. For the first time, the observation of a vanishing and a negative differential resistivity of the a‐Si:H barriers even at room temperature is reported. It is concluded that there is no real quantum confinement in heterostructures based on amorphous semiconductors.
Hydrostatic Deformation Potentials and Phase Transitions in CuGa(SxSe1−x)2 Alloys at High Pressure
Authors: González J. , Calderón E. , Capet F. 
Published: July 2007

AbstractThe optical absorption edge of CuGa(SxSe1−x)2 single crystals is measured as a function of hydrostatic pressure, covering the full stability range (0 to 30GPa) of the chalcopyrile phase. For 0 ⩽ x ⩽ 1, a linear increase of the direct energy gap with pressure is found. The corresponding gap deformation potential is calculated to be −4.5 eV for x = 0, −5.2 eV for x = 0.5, and −4.4 eV for x = 1. From changes in the light transmission characteristic of the samples under pressure, structural first‐order phase transitions are observed.
Electronic and Structural Properties of the Liquid (Tl1/2Pb1/2)‐Se System
Authors: Usuki T. , Itoh K. , Aita S. , Kameda Y. , Uemura O. 
Published: July 2007

AbstractThe electrical conductivity, magnetic susceptibility, and thermoelectric power in the liquid (Tl1/2Pb1/2) Se system are measured over wide temperature and composition ranges. It is observed that the electrical conductivity in the system sharply falls near the stoichiometric composition of Tl2Pb2Se3 and the magnetic susceptibility has a diamagnetic maximum at this composition, where the thermoelectric power changes its sign. In addition, the DTA investigation shows that the liquidus temperature of the system has a maximum around this composition. These results suggest that a short‐range order appears around the composition of Tl2Pb2Se3 in the liquid (Tl1/2Pb1/2)‐Se system. The delocalized electron analysis using both susceptibility and conductivity data suggests that the bonding nature of liquid Ti2Pb2Se3 is rather ionic. The radial distribution study by neutron diffraction also exhibits that the first peak position of g(r) for liquid Tl2Pb2Se3 is located near the ionic bond distance of metal and chalcogen atoms. On the other hand, covalent Se‐ Se bonds are formed in the Se‐rich composition range.
On the Phenomenological Theory of the Coherent Photogalvanic Effect in Glass
Authors: Sokolov V. O. , Sulimov V. B. 
Published: July 2007

AbstractIn connection with the charge‐separation model of photoinduced second‐harmonic generation in optical fibres based on the coherent photogalvanic effect the tensorial properties of the coherent photocurrent in glass are studied using a phenomenological approach with the randomness of the glass taken into account. Since the most general expression is used for the coherent photocurrent, this approach is valid for any microscopic model of the coherent photogalvanic effect. The dependence of the photocurrent on the polarization of fundamental and second‐harmonic waves is obtained. Directional photoionization of localized states is studied explicitly in connection with experiments with circularly polarized waves performed recently.
Device Structures and Characteristics of Laser Diodes with ZnMgSSe Cladding Layers
Authors: Ohata T. , Itoh S. , Nakayama N. , Matsumoto S. , Nakano K. , Ozawa M. , Okuyama H. , Tomiya S. , Ikeda M. , Ishibashi A. 
Published: July 2007

AbstractZnSe based laser diodes exhibit best initial performances such as low threshold current with ZnCdSe/ZnSSe/ZnMgSSe SCH‐SQW structure. The device lifetime is improved with the ZnCdSe/ZnSSe/ZnMgSSe SCH‐MQW structure. Laser emission of 471 nm wavelength is obtained under pulsed injection at room temperature with ZnSe/ZnMgSSe DH structure.
MBE of ZnSe Alloys to Achieve Room Temperature CW Laser Diodes
Authors: Han Jung , Gunshor R. L. , Nurmikko A. V. 
Published: July 2007

AbstractIssues related to the growth and characterizations of II–VI blue‐green laser diodes are reviewed. The development of the Zn(Se, Te) graded contact scheme to p‐ZnSe is found to be effective in supporting the room‐temperature CW operation of green (508 nm) laser diodes with a threshold voltage of 5.8 V. Compositional control of the ZnMgSSe cladding layers and the reduction of nonradiative point defects in the ZnCdSe quantum wells will be discussed. The observation of persistent photoconductivity in nitrogen‐doped p‐ZnMgSSe at low temperature is reported. The increase of conductivity after illumination appears due to a metastable population of holes which are in thermodynamic equilibrium with hydrogenic acceptors having reduced activation energy. The experimental evidence suggests the presence of a DX‐like behavior for holes.