bluuebunny/crossref_metadata_2025_split huggingface dataset:
An upwind finite volume scheme and its maximum‐principle‐preserving ADI splitting for unsteady‐state advection‐diffusion equations
Authors: Wang Hong , Zhao Weidong 
Published: February 2003

AbstractWe develop an upwind finite volume (UFV) scheme for unsteady‐state advection‐diffusion partial differential equations (PDEs) in multiple space dimensions. We apply an alternating direction implicit (ADI) splitting technique to accelerate the solution process of the numerical scheme. We investigate and analyze the reason why the conventional ADI splitting does not satisfy maximum principle in the context of advection‐diffusion PDEs. Based on the analysis, we propose a new ADI splitting of the upwind finite volume scheme, the alternating‐direction implicit, upwind finite volume (ADFV) scheme. We prove that both UFV and ADFV schemes satisfy maximum principle and are unconditionally stable. We also derive their error estimates. Numerical results are presented to observe the performance of these schemes. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 211–226, 2003
Adaptive numerical solution of thick plates using first‐order shear deformation theory. Part II: Adaptivity
Authors: Ludwig M. J. , Shaw Simon , Whiteman J. R. 
Published: February 2003

AbstractThis is the second in a pair of articles concerned with the adaptive finite element solution of Riessner‐Mindlin thick plates modeled using first‐order shear deformation theory. This article is concerned with enhancing the a posteriori energy‐error estimators developed in Part I in order to accomodate transition elements in the finite element mesh. The resulting estimators are then used in an adaptive finite element model employing transition elements and the subsequent results discussed and compared with those in Part I. A major part of the article is devoted to identifying a novel patch assembly node algorithm for using the ZZ recovery‐type estimator with transition elements. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 19: 227–253, 2003.
Thermo‐ and galvanomagnetic measurements of semiconductors at ultrahigh pressure
Authors: Shchennikov Vladimir V. , Ovsyannikov Sergey V. 
Published: February 2003

AbstractThe thermoelectric power, magnetoresistance, and thermomagnetic effects were measured for Te and Se micro‐samples in the vicinity of semiconductor–metal phase transitions at high pressure. From longitudinal and transverse Nernst‐Ettingshausen effects the scattering parameterrof holes was estimated and a decrease of the effective mass of holes was found during the closing of semiconductor gap. After the high pressure treatment an inversion of the sign of parameterrcorresponding to a change of scattering mechanism was observed for the Te sample due to an increase of the density of lattice defects.
THz lasing due to resonant acceptor states in strained p‐Ge and SiGe quantum‐well structures
Authors: Kagan M. S. , Altukhov I. V. , Chirkova E. G. , Sinis V. P. , Troeger R. T. , Ray S. K. , Kolodzey J. 
Published: February 2003

AbstractAn intense THz emission was observed from strained SiGe/Si quantum‐well structures under a strong pulsed electric field. The p‐type structures were MBE‐grown on n‐type Si substrates and δ‐doped with boron. Lines with wavelengths near 100 microns were observed in the emission spectrum. The modal structure in the spectrum gave evidence for the stimulated nature of the emission. The origin of the THz emission was attributed to intra‐center optical transitions between resonant and localized boron levels similar to that in compressed p‐Ge.
Hydrostatic pressure coefficients of the valence band maximum in Ge, InSb, InAs, and GaAs
Authors: Daunov M. I. , Kamilov I. K. , Gabibov S. F. , Magomedov A. B. 
Published: February 2003

AbstractThe Hall coefficient R and specific resistance ρ have been measured in p‐InSb:Cr, with a hole concentration of about 1012 cm–3 at T = 77 K, as a function of pressure up to P = 1.5 GPa at T = 77 and 300 K. The deep acceptor level is found to be located at the distance εA2 = 0.11 eV from the top of the valence band. The pressure coefficient of the valence band maximum ∂εV/∂P was determined relative to the vacuum in semiconductors Ge, InSb, InAs, and GaAs.
Electronic and structural study of β‐FeSi2 under high pressure
Authors: Mori Y. , Ikai T. , Teranishi R. , Takarabe K. 
Published: February 2003

AbstractHigh‐pressure X‐ray and optical studies of β‐FeSi2 were carried out up to 60.7 GPa and 5 GPa, respectively. The bulk modulus was determined to be (243.46 ± 7.14) GPa by the Birch‐Murnaghan equation. A new phase appeared at about 20 GPa. The pressure coefficient of the direct bandgap was determined to be +15.9 meV/GPa by the high‐pressure optical absorption experiment. Consequently the deformation potential for the direct bandgap was determined to be –3.87 eV. The deformation potential for the direct gap at the Y point was obtained to be –2.4 eV using a FLAPW (full‐potential linearized augmented plane wave) method.
The effect of pressure on the radiative efficiency of InAs based light emitting diodes
Authors: Choulis S. A. , Andreev A. , Merrick M. , Jin S. , Clarke D. G. , Murdin B. N. , Adams A. R. , Krier A. , Sherstnev V. V. 
Published: February 2003

AbstractThe spontaneous emission of 3.3 μm light emitting diodes (LEDs) and lasers based on InAs alloys were studied as a function of hydrostatic pressure. An increase in light output with increasing pressure has been observed, with a general comparison of the performances of type I and type II structures given in terms of the radiative and non‐radiative processes involved. The experimental results provide evidence that the so‐called CHSH Auger process is insignificant in these devices. However, Auger recombination mechanisms are still shown to dominate the response of these type II LEDs in contrast to type I lasers where competing radiative processes appear more significant.
Anomalous pressure dependence of acoustic phonons of AgGaSe2 investigated by inelastic neutron scattering to 4.3 GPa
Authors: Klotz S. , Derollez P. , Fouret R. , Braden M. , Hennion B. , Hubert Ch. , Meducin F. , Łażewski J. , Gonzalez J. 
Published: February 2003

AbstractThe pressure dependence of the transverse acoustic (TA) phonons along [100] and [001] and the low‐frequency optical Λ3 modes of AgGaSe2 has been measured at pressures to 4.3 GPa by inelastic neutron scattering. We find an exceptionally strong frequency decrease of the TA modes with Grüneisen parameters as low as –10 for wave vectors close to the zone centre. The associated elastic coefficient C44 decreases by ∼50% between 0 and 2.6 GPa. The softening also affects the optical modes to a less extent. These lattice dynamical anomalies seem to be related to a continuous structural phase transition located at ∼2.6 GPa. Single crystal X‐ray diffraction results are consistent with a monoclinic lattice of the high pressure phase which can be regarded as a slightly distorted chalcopyrite structure, similar to AgGaS2.
High pressure structural phase transitions in IV–VI semiconductors
Authors: Ahuja Rajeev 
Published: February 2003

AbstractWe have studied high pressure structural phase transitions in lead chalcogenides by means of first principles total energy calculations within the generalized gradient approximation (GGA) using the full potential linear‐muffin‐tin‐orbital (FPLMTO) method. These compounds are stable in the NaCl‐type structure at ambient conditions and transform to the CsCl‐type of structure under high pressure through an intermediate phase. The experimental data suggests that this intermediate phase could be either the TlI‐type phase or the GeS‐type phase. However this data was not enough to solve the full structural refinement. So we have performed fully relaxed total energy calculations to get the full structure of this intermediate phase. Our calculated transition pressures are in very good agreement with experiment.
The effect of anisotropic intermolecular interactions on the pressure response of polymeric fullerenes
Authors: Arvanitidis J. , Assimopoulos S. , Papagelis K. , Ves S. , Prassides K. , Iwasa Y. , Kourouklis G.A. 
Published: February 2003

AbstractHigh pressure Raman scattering was used to probe the pressure response of the two‐dimensional tetragonal and rhombohedral C60 polymers. The phonon frequencies as a function of pressure for the various Raman modes of the polymeric phases show a slope change near ∼4 GPa. As pressure increases above 4 GPa, the pressure coefficients for the majority of the modes exhibit reversible change to lower values. These changes may be attributed to a possible structural modification of the polymers from their initial state, which is characterized by highly anisotropic intermolecular interactions (strong in‐plane covalent bonds and weak out‐of‐plane van der Waals interactions), to a more isotropic one upon application of the external pressure. This behavior is a common theme of other fullerene materials displaying bonding anisotropy.
Thermoactivated conductivity in p‐GaAs/Al0.5Ga0.5As below 5 K under combined influence of illumination and uniaxial stress
Authors: Kraak W. , Minina N. Ya. , Ilievsky A. A. , Sorensen C. B. , Berman I. V. 
Published: February 2003

AbstractStrongly thermoactivated negative photoconductivity in p‐GaAs/Al0.5Ga0.5As doped with Be is observed under the combined influence of illumination by a red light emitting diode and uniaxial compression at liquid helium temperatures. The effect can be described in a model with deep donor‐like traps at the heterointerface below the Fermi level, if a barrier between the ground and excited donor‐like states EB = 6 meV is introduced. The barrier does not depend on uniaxial stress that governs the strong resistivity on temperature dependence mainly by the reduction of 2D hole concentration and 2D hole mobility both in dark and under illumination.
Reliable non‐linear elastic constants
Authors: Dunstan D. J. , Bosher S. H. B. 
Published: February 2003

AbstractThe values given in the literature for the third‐order elastic constants cIJK of the standard semiconductors have long been suspect. We have applied modern statistical analysis to the raw data from which the databook cIJK were obtained, and we give revised values with reliable error estimates for Si, Ge and GaAs. The databook cIJK are appropriate for an expansion of the elastic energy of a body as a Taylor series in Lagrangian strain ηIJ, but there are formidable mathematical difficulties in using Lagrangian strain in the analysis of physical problems. To facilitate such analysis, we introduce effective second‐order elastic constants for materials under finite strain. From these, strain, stress and pressure derivatives are readily calculated. The pressure derivatives are given for Si, Ge and GaAs. Using the stress derivatives, the relationships between physical observables such as acoustic velocities and the databook cIJK can be obtained by simple algebra.
High‐pressure photoluminescence study of the electronic structure of InP/GaP quantum dots
Authors: Kristukat C. , Goñi A.R. , Hatami F. , Dreßler S. , Masselink W.T. , Thomsen C. 
Published: February 2003

AbstractThe electronic subband structure of self‐assembled InP/GaP quantum dots (QDs) has been investigated by means of photoluminescence (PL) measurements as a function of hydrostatic pressure up to 8 GPa and temperature. At ambient pressure the PL emission of the sample arises from direct optical transitions between the lowest electron and hole Γ‐point states confined in the QDs. At a very low pressure of about 0.15 GPa, the Γ–X conduction band crossover occurs, after which the PL emission of the dots becomes roughly 20 times weaker in intensity and its energy exhibits the slight redshift typical of indirect recombination processes from the conduction band X valleys. Our results indicate a type‐I band alignment for the strained InP/GaP dot structure at low pressure and yield a value of 300 ± 30 meV for the valence‐band offset.
Correlation between lasing properties and band alignment of edge emitting lasers with (Ga,In)(N,As)/Ga(N,As) active regions
Authors: Grüning H. , Klar P. J. , Heimbrodt W. , Weiser G. , Koch J. , Nau S. , Stolz W. , Fehse R. , Adams A. R. , Ramakrishnan A. , Ebbinghaus G. 
Published: February 2003

AbstractWe have investigated the optical properties of edge‐emitting laser structures containing three Ga0.7In0.3N0.005As0.995 quantum wells embedded in GaNxAs1–x barriers grown by metal‐organic vapour‐phase epitaxy. In a series of three samples the nitrogen content x of the barrier was varied from 0% to 3%. We studied the optical transitionsand the threshold of these laser structures by using pressure‐dependent photomodulated reflectance (PR) up to 20 kbar at room temperature. Additionally we measured the pressure dependence of the lasing energy and the threshold current of the corresponding laser structures as function of hydrostatic pressure. Due to the large red‐shift of the Ga(N,As) band gap with increasing N of about 150 meV per percent N, the variation of x leads to a considerable change of the carrier confinementof holes and, in particularly, of electrons. The strong increase of the threshold current of the laser device with pressure suggests a swiftly increasing threshold carrier density due to the increasing effective mass and non‐parabolicity.an enlarged carrier density at threshold Comparing the pressure dependence of the lasing energy and the conduction band edge furthersupports this conclusion.
Pressure dependence of optical phonons in ZnCdSe alloys
Authors: Camacho J. , Loa I. , Cantarero A. , Syassen K. , Hernández‐Calderón I. , González L. 
Published: February 2003

AbstractWe report on resonant Raman scattering measurements under hydrostatic pressure and at low temperature on two ZnxCd1–xSe alloy films, which were grown by different epitaxial techniques on GaAs. This ternary alloy exhibits an intermediate (I) mode between the typical transverse (TO) and longitudinal optical (LO) modes of the zinc‐blende structure. The shift of the vibrational frequencies of the three modes with pressure is analyzed. The Grüneisen parameters of these three optical modes are determined. Moreover, overtones of the LO modes as well as TO + nLO and I + nLO zone‐center phonon combinations are observed.
Ab initio study of BAs under pressure
Authors: Herrera‐Cabrera M. J. , Rodríguez‐Hernández P. , Muñoz A. 
Published: February 2003

AbstractWe use an ab initio total energy pseudopotential technique within the Density Functional Theory in the local‐density approximation to determine the vibrational normal modes (phonons) defined within the first Brillouin Zone of BAs. We also study the effects of hydrostatic pressure on these phonons and the mode Grüneisen parameters using the response‐function formalism for the computation. There is a very good agreement between the transversal optical phonon frequency at the Γ point calculated on this way and that with the frozen phonon technique. We also study the electronic band structure, the band‐gap pressure dependence and the generalized stability criteria.
Theoretical study of ZnS under high pressure
Authors: López‐Solano J. , Mujica A. , Rodríguez‐Hernández P. , Muñoz A. 
Published: February 2003

AbstractThe structural phase transformations under pressure of ZnS are studied within the density functional formalism, using the local density approximation and pseudopotential scheme. We show results in agreement with the well‐established zinc‐blende and NaCl phases present at low pressures, and also confirm a recently proposed Cmcm structure found experimentally by Desgreniers et al. [Phys. Rev. B 61, 8726 (2000)] to be more stable than NaCl at pressures higher than 65 GPa.
First‐principles study of phonon‐mode softening under pressure: the case of GaN and AlN
Authors: Wagner J.‐M. , Bechstedt F. 
Published: February 2003

AbstractThe origin of the mode softening under pressure of the low‐frequency E2 phonon of GaN and AlN is investigated by first‐principles density‐functional calculations. Using the eigenvectors of these modes as obtained from diagonalizing a dynamical matrix which is calculated using density‐functional perturbation theory, a frozen‐phonon calculation shows that the softening is mainly caused by an increased destabilization due to the Ewald energy, which is nearly counterbalanced by the other contributions to the total energy in the case of AlN, but only partially so for GaN.
Wavelength dependence of the modal refractive index in 1.3 μm InGaAsP, AlGaInAs and GaInNAs lasers using high pressure
Authors: Jin S. R. , Sweeney S. J. , Adams A. R. , Higashi T. , Riechert H. , Thijs P. J. A. 
Published: February 2003

AbstractWe report the variation of the modal refractive index at threshold with lasing wavelength in 1.3 μm InGaAsP, AlGaInAs and GaInNAs multiple quantum well lasers by measuring mode spectra under pressure up to 15 kbar. It is shown that the decrease of index with lasing wavelength is about 4% on average in the pressure range studied. We also find that the modal refractive index reduces with increasing injection current and is very sensitive to the injection current around laser threshold.
Pressure dependence of photoluminescence spectra of self‐assembled InAs/GaAs quantum dots
Authors: Manjón F.J. , Goñi A.R. , Syassen K. , Heinrichsdorff F. , Thomsen C. 
Published: February 2003

AbstractPhotoluminescence (PL) measurements have been performed in InAs/GaAs self‐assembled quantum dots (QDs) under high excitation conditions at low temperatures and under high hydrostatic pressures up to 10 GPa. Mechanically polished samples for high pressure experiments exhibited PL emission from the QD ground state but not from the excited states. Instead, a new broad band is observed in the energy range of the first excited state, which is tentatively attributed to emission from smaller dots formed during the mechanical thinning of the sample. With increasing pressure we found a similar blue shift for the PL maxima of the QD ground state (65 meV/GPa) and of the new broad band (69 meV/GPa). These pressure coefficients are 20% and 40% lower than those reported for dots of less than half the height as in our case and for the wetting layer, respectively. Our results point to a systematic reduction of the pressure coefficient of the InAs QDs with the increase of the dot height.
Raman scattering under pressure and the phase transition in ε‐GaSe
Authors: Kulibekov A. M. , Olijnyk H. P. , Jephcoat A. P. , Salaeva Z. Y. , Onari S. , Allakhverdiev K. R. 
Published: February 2003

AbstractRaman scattering in ε‐GaSe has been investigated at room temperature in a diamond anvil cell by using helium gas as a pressure transmitting medium. The first observation of the solid–solid phase transition under pressure from a hexagonal structure at ambient pressure to a NaCl‐type at around 29.2 GPa is reported. A photoinduced change in the pressurised crystal was observed. The transition under pressure was found to be irreversible at room temperature. It was shown that the pressurised form of ε‐GaSe at ambient conditions most probably belongs to the γ‐type as characterised by an increased intensity of the Raman modes at 234 cm–1 and 250 cm–1.
Pressure induced phase transitions of BNs
Authors: Shirai K. , Fujita H. , Katayama‐Yoshida H. 
Published: February 2003

AbstractPhase stability and phase transitions of boron nitride polymorphoic modifications have been re‐examined by using a first‐principles pseudopotential method based on the local‐density approximation. In order to study systematically, the graphite–diamond transition is also examined. The present result again confirms that the dense form is more stable than the layered form. However, this might not be conclusive, because the accuracy of the used exchange‐correlation functionals has yet been established.
Electrical resistivity of Cu doped As–Se glasses at high pressure
Authors: Ramesh K. , Ramesh Rao N. , Sangunni K. S. , Gopal E. S. R. 
Published: February 2003

AbstractElectrical resistivity measurements have been performed on CuxAs40Se60–x glasses with x between 0 and 28 at% of Cu. The resistivity of these glasses continuously decreases and saturates at higher quasi‐hydrostatic pressures. The pressure derivative of the electrical resistivity shows distinct changes as a function of composition; a large change for the initial addition of Cu (≤ 10 at% Cu) and levelling off for higher content of Cu. To understand this, Differential Scanning Calorimetric (DSC) and thermal crystallization studies have been carried out on all these glasses. Thermal crystallization of As–Se glasses with 5 and 10 at% Cu results in crystalline Cu3AsSe4 and As2Se3 phases, whereas glasses with 15 and 20 at% of Cu crystallize into Cu3AsSe4 phase only. Glasses with 25 and 28 at% of Cu yield a new binary Cu2As3 and the ternary Cu3AsSe4 phase. These structural differences arising as a function of composition are reflected in the pressure derivative of the resistivity of the glasses.
High‐pressure studies of the recombination processes, threshold currents, and lasing wavelengths in InAs/GaInAs quantum dot lasers
Authors: Marko I.P. , Andreev A.D. , Adams A.R. , Krebs R. , Reithmaier J.P. , Forchel A. 
Published: February 2003

AbstractThe threshold current of broad area GRINSCH InAs quantum dot (QD) lasers has been measured as a function of hydrostatic pressure in the range of 0–12 kbar. The laser emission photon energy, Elaser, increases linearly with pressure, p, at 10.1 meV/kbar and 8.3 meV/kbar for 980 nm and 1.3 μm QD lasers, respectively. For the 980 nm QD lasers the threshold current increases with pressure at a rate proportional to the square of the photon energy, E2laser. However, the threshold current of the 1.3 μm QD laser decreases by 26% over a 12 kbar pressure range, demonstrating the importance of the Auger recombination in 1.3 μm QD lasers. The results are discussed in the framework of a theoretical model based on the electronic structure and radiative recombination calculations carried out using an 8 × 8 k · p Hamiltonian.
Proceedings of the Tenth International Conference on High Pressure Semiconductor Physics (HPSP‐X)
Authors: Murdin Ben 
Published: February 2003

AbstractThe Tenth International Conference on High Pressure Semiconductor Physics (HPSP‐X) was held as a satellite meeting of the International Conference on the Physics of Semiconductors in Guildford from 5 to 8 August 2002. It brought together scientists and engineers who use high pressure to study the science and technology of semiconductors. The HPSP‐X conference reviewed the latest issues and developments in the physics of both bulk and low‐dimensional semiconductor materials and devices under pressure. It covered all aspects of fundamental and applied high‐pressure semiconductor research, including experimental and theoretical investigations under isotropic or anisotropic stress conditions. Topics such as electronic structures, vibrational and optical properties, transport phenomena, defect states, phase transitions, and novel materials or structures are included in this issue.Following the meetings HPSP‐VII in Schwäbisch Gmünd, phys. stat. sol. (b) 198, No. 1 (1996); HPSP‐VIII in Thessaloniki, phys. stat. sol. (b) 211, No. 1 (1998), and HPSP‐IX in Sapporo, phys. stat. sol. (b) 223, No. 1/2 (2001), the proceedings of this successful conference series are published in physica status solidi for the fourth time.