摘要:

AbstractLocalised vibrational modes (LVMs) associated with DX centers in AlxGa1−xAs and n‐type AlxGa1−xAs are worked out from a molecular model, introducing the relaxation. Preliminary studies indicate that some of the basic features observed from deep level transient spectroscopy (DLTS) can be viewed from the present calcula

ISSN:0370-1972    

DOI:10.1002/pssb.2221870106

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractReflectivity spectra of CuAlS2, CuAlSe2, and CuGaSe2crystals have been investigated in the wave number range 50 to 600 cm−1for the polarizationsE‖candE⊥c. The fundamental phonon parameters, the limiting dielectric constants ε∞and εSand the reflectivity spectra contours have been calculated by using classical dispersion relations for bothE‖candE‖cconfigurations. 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

ISSN:0370-1972    

DOI:10.1002/pssb.2221870107

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe dependence of the photoionization cross‐section on photon energy is calculated for shallow donors in finite‐barrier GaAs/Ga1−xAlxAs quantum wells as well as the binding energy as a function of well width. The effect of a magnetic field is also consi

ISSN:0370-1972    

DOI:10.1002/pssb.2221870108

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThin chromium films of thickness ranging from 25 to 80 nm are prepared by thermal evaporation under a vacuum of 1.33 × 10−3Pa. 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 pathl0, carrier concentrationnc, relaxation time τ, and Fermi energyEF. The optical constants,nandk, 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 ofnc, σs,l0, and τ obtained electrically are found to match with those obtained opti

ISSN:0370-1972    

DOI:10.1002/pssb.2221870109

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

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 experimentall

ISSN:0370-1972    

DOI:10.1002/pssb.2221870110

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

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 × 10−8and 10−5ω−1cm−1for 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 10−10Ω−1cm−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 × 105V/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 heterostructur

ISSN:0370-1972    

DOI:10.1002/pssb.2221870111

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractUsing a simplified parabolic band model approach within the framework of the envelope function approximation, the influence of in‐plane magnetic fields on the electronic and optical properties of type‐I superlattices is studied. The results are in qualitative agreement with experimental facts previously reported, as well as with previous theoretical results obtained using more elaborated and toilsome methods. Furthermore, this approach allows to advance, in a great extent, in the analytical treatment of interband transitions, leading straightforwardly to some general conclusions. The not well understood case of high magnetic field effects (magnetic length comparable with the superlattice period) is studied in detail. There strong variations of the interband transition strengths as function of the cyclotron orbit center position are found, a fact which is directly connected with the broadening and final saturation of the magneto‐absorption spectrum with increasing fields. A consistent explanation of such strong variations is given in terms of magnetic subband m

ISSN:0370-1972    

DOI:10.1002/pssb.2221870112

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe electronic structure of the layered compound RuCl3is studied by means of X‐ray photoelectron spectroscopy and angle‐resolved ultraviolet photoelectron spectroscopy. The energy distribution curves are measured along different azimuthal directions ΓM, ΓM′, and ΓK in the Brillouin zone. The experimental valence bands of RuCl3consisting of an uppermost non‐dispersive band of d symmetry at about 2 eV above the top of the valence p band, and two dispersive bands of p symmetry are studied by application of theE(k‖) method. The nature of the valence bands of RuCl3, are discussed in relation to the electronic structure of the metal RuO2owing to their similar X‐ray photoel

ISSN:0370-1972    

DOI:10.1002/pssb.2221870113

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe optical absorption edge of CuGa(SxSe1−x)2single 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 forx= 0, −5.2 eV forx= 0.5, and −4.4 eV forx= 1. From changes in the light transmission characteristic of the samples under pressure, structural first‐order phase transitions

ISSN:0370-1972    

DOI:10.1002/pssb.2221870114

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

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 Tl2Pb2Se3and 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 Tl2Pb2Se3in the liquid (Tl1/2Pb1/2)‐Se system. The delocalized electron analysis using both susceptibility and conductivity data suggests that the bonding nature of liquid Ti2Pb2Se3is rather ionic. The radial distribution study by neutron diffraction also exhibits that the first peak position of g(r) for liquid Tl2Pb2Se3is 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 compositio

ISSN:0370-1972    

DOI:10.1002/pssb.2221870115

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY