摘要:

The first observations of stacking-fault tetrahedra in ion-implanted III-V compounds are reported. The structure and orientation of the stacking-fault tetrahedra are briefly described. The tetrahedra are present in the near-surface region that recrystallized during the annealing. High-resolution images suggest that the stacking-fault tetrahedra are of the vacancy type.

ISSN:0950-0839    

DOI:10.1080/09500838708205254

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The dependence of the normal-state resistivity, resistive superconducting transition (Tc, ΔTc), and of the upper critical-field slope (dHc2/dT|T=Tc) on density has been investigated for several YBa2Cu3O9-x(x⋍2.1) samples. The resistivity decreases rapidly with increasing density, whereasTcand ΔTcare rather insensitive to a change in density. dHc2/dT|Tcdepends sensitively on the preparation conditions. The implications of these results both for the evaluation of the parameters relevant to the understanding of the nature of superconductivity and for the technological applications of granular superconductors are briefly discussed.

ISSN:0950-0839    

DOI:10.1080/09500838708205255

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We show that in disordered metallic systems, spin-orbit interactions lead to the existence of two metallic phases separated in temperature. The low-temperature metallic phase arises from spin-orbit interactions. The crossover temperature is proportional to (Z-Z′)2(Zis the atomic number of the donor andZ′that of the matrix) and is expected to be observable for donors with large atomic numbers. The presence of two metallic phases implies two mobility edges, existing at different temperatures, and affecting the conductivity when the Fermi energyEFlies below the mobility edgeEcWe thus predict anomalies in the conductivity in this range of concentration, consistent with the measurements of Long and Pepper on Si:Sb.

ISSN:0950-0839    

DOI:10.1080/09500838708205256

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An analysis of extended X-ray absorption fine structure (EXAFS) measurements at the Mn K-edge of the α-crystalline and icosahedral (i) phases of MnAlSi indicates that the icosahedral cage of Mn atoms that is part of the common structural unit in both phases retains its cubic distortion in the i-phase. Neither a quasicrystalline nor a randomly connected icosahedron (icosahedral glass) model is in agreement with this experimental result. A model that is consistent with the new EXAFS results and other properties of the i-phase of MnAlSi is one in which ∼40 Å crystallites of the α-phase are oriented icosahedrally along the threefold directions of the structural unit.

ISSN:0950-0839    

DOI:10.1080/09500838708205257

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We present a simple analytical approach for determining both the mean transport energy of carriers hopping within an exponential distribution of tail states and their mean transit time in the dispersive transport regime. Good agreement with computer simulations is found.

ISSN:0950-0839    

DOI:10.1080/09500838708205258

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A recent letter by Kakalios (1987) has criticized our suggestion that the microscopic mobility of hydrogenated amorphous silicon increases under high-level double injection. In this Letter, we show that Kakalios misinterpreted our model and misrepresented our data.

ISSN:0950-0839    

DOI:10.1080/09500838708205259

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor