摘要:

AbstractThe method developed in Parts I, II for calculating the polarization energy of crystals by point defects self‐consistently with their electronic structure is extended. (i) Along with the initial (e.g. ground) state the final (e.g. excited) electronic state of the crystal containing the defect and the corresponding vertical transition energy is considered. (ii) The uncompensated charge density simulating the defect and its neighbourhood is treated now by a set of non‐point charges. (iii) The polarization potential is calculated. This generalized method may be useful for self‐consistent calculations of a wide class of actual point defects in ionic s

ISSN:0370-1972    

DOI:10.1002/pssb.2221370125

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe multimode Jahn‐Teller effect for the tetrahedral2T2term coupled with E and T2vibrations is discussed taking into account the spin—orbit interaction. Harmonic vibrations are considered at the trigonal minimum point of the lowest sheet of the adiabatic potential. Using the Green's function method the redetermined projected densities of states are obtained. The one‐phonon sideband of the2E →2T2transition is expressed in terms of projected densities and compared with the experimental data for2E →2T2luminescence of

ISSN:0370-1972    

DOI:10.1002/pssb.2221370126

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe temperature dependence of Mössbauer quadrupole splitting of57Fe2+in GeFe2O4is theoretically analysed by taking into account the effect of orbit—lattice interactions from 77 to 1000 K. It shows a good agreement between theoretical and experimental results, brings consistency between Mössbauer and magnetic susceptibility measurements, and emphasizes the importance of the dynamic crystal field approach over a wide range of temperatu

ISSN:0370-1972    

DOI:10.1002/pssb.2221370127

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractData on position and lifetime of the photoluminescence band in Cd1−xMnxTe and Zn1−xMnxTe are reported for different manganese concentrationsx. The luminescence is due to intraatomic transitions within the manganese ions. The blue shift at low temperatures shows the typical behavior of an exchange dependent parameter. The lifetimes are in the microsecond range. At low temperatures the decay is dominated by the radiative lifetime with weak temperature dependence. In Zn1−xMnxTe the lifetime varies with manganese concentration, whereas in Cd1−xMnxTe the concentration dependence is insign

ISSN:0370-1972    

DOI:10.1002/pssb.2221370128

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe damping properties of surface phonon‐polaritons, especially long‐range surface phonon‐polaritons in bilayer systems are analysed. An analytic expression is derived for the damping function by means of a perturbative method. The different behaviour of the damping properties of surface phonon‐polaritons for various physically different bilayer systems are discussed. It is shown that not all possible cases yield long‐range surface phonon‐polaritons. In some cases one or two modes show the behaviour of long‐range surface phonon‐polaritons. In special cases, there two longe‐range surface phonon‐polariton modes exist, one of these shows in a small frequency range a significantly increased propagation length. The propagation properties are analyzed numerically in dependence of frequency and of the thicknesses of the two layers of the bilayer system. Dispersion curves, the electromagnetic fields, the energy flow, the power flow, and the propagation length of the surface phonon‐polaritons are given in graphic

ISSN:0370-1972    

DOI:10.1002/pssb.2221370129

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA detailed investigation is made of the Ga3 luminescence spectrum observed in gallium doped silicon after electron irradiation and annealing at ≈ 250 °C. The spectrum exhibits exciton singlet—triplet pair no‐phonon transitions at 0.9291 or 0.9272 eV, respectively, and quasi‐localized modes of vibration energy 10.3, 24.4, and 56.9 meV along with combination modes and lattice phonon bands. An additional higher energy no‐phonon transition is due to an excited exciton state at excess energy of 3.8 meV thermalizing with the singlet—triplet states. The isotropic Zeeman splitting of the triplet (g= 2.00 ± 0.05) shows that the orbital momentum of the excitonic hole is entirely quenched. This and the low thermal dissociation energy of the exciton (16 meV) are used to deduce a strong hole binding energy (≈ 226 meV) whereas the 16 meV energy is attributed to the electron localization. The low electron binding energy is consistent with uniaxial stress measurements which are quantitatively explainable in terms of effective‐mass valley—orbit electron states. This defect represents the first example of a luminescent center in silicon which under uniaxial stress exhibits the whole multiplicity of valley—orbit‐states. The valley—orbit nature of the electron and the quenching of the hole orbital momentum render a symmetry classification

ISSN:0370-1972    

DOI:10.1002/pssb.2221370130

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Ga2 spectrum with its no‐phonon transitions at 1.0472 eV (triplet) and 1.0501 eV (singlet) is studied as a function of temperature and in magnetic and uniaxial stress fields. Like in the case of Ga3, this singlet—triplet pair exciton emission is accompanied by thermalizing higher energy singlet lines s (+2.9 meV), s*(+3.8 meV), and s**(+4.7 meV). Localized vibrational mode replicas of the triplet/singlet are observed with ħω = 11.0 meV and ħω = 18.8 meV, along with lattice modes and combination lines. Zeeman measurements indicate that the center belongs to the rhombic I (C2v) point group symmetry, and the triplet transition splits asgx= 2.7,gy= 2.1, andgz= 1.6. The effectiveg‐value of the exciton,geff= 2.13, is consistent with thermal data suggesting the hole to be the tightly bound particle (≈100 meV) whereas the electron is bound by only ≈23 meV. Uniaxial stress measurements can be explained in terms of valley—orbit interactions by the weakly bound “pseudo‐donor” electron. Finally, the gallium related centers Ga 1, Ga2,

ISSN:0370-1972    

DOI:10.1002/pssb.2221370131

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe possibility of a negative momentum relaxation rate by absorption of polar optical phonons in a non‐degenerate semiconductor is examined. Charge density wave propagation is predicted as a result of this. The wave sets up an average dc field in which the electrons respond in such a way that a dc current independent of the external field flows. This implies that a persistent current could flow in the soli

ISSN:0370-1972    

DOI:10.1002/pssb.2221370132

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractBased on the one‐electron version of the Kubo formula and assuming only the elastic scattering of carriers on static impurities the quantum oscillations of the transport coefficients are evaluated of two‐dimensional electron systems in weak/intermediate magnetic fields. The changes in the oscillating pattern due to the variation of the magnetic field, the carrier density, and the temperature are investigated. Numerical examples give results in qualitative agreement with recent experimental d

ISSN:0370-1972    

DOI:10.1002/pssb.2221370133

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Poole‐Frenkel effect is often observed in the field‐dependent properties of amorphous materials. Experimentally, it is frequently found that the slopes of log σ versusE1/2plots differ from that predicted by the Poole‐Frenkel equation and several theorems have been postulated to explain this discrepancy. Recently, Török used the concept of multiple ionisation to account for such discrepancies. In this paper some of the arguments presented by Török and others is examined in more detail, and the Poole‐Frenkel effect is discussed for two limiting cases. The situation when the free carrier density (n) in the case of an n‐type material containing both donor (Nd) and acceptor (Na) impurities, is of the same order of magnitude asNawhere the two approximations are invalid, is more closely examined. It is shown that by assuming a field dependent value ofn, a transition region situated between the two approximations is evident. It is also shown that by considering basic parameters such as temperature, and acceptor densities, a Poole‐Frenkel plot is obtained which is very sensitive to variations in temperature and

ISSN:0370-1972    

DOI:10.1002/pssb.2221370134

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY