摘要:

A quantum‐mechanical calculation of the conduction cyclotron mass in GaAs‐(Ga,Al)As superlattices in an in‐plane magnetic field is performed. Calculation is carried out in the envelope function approximation using the parabolic and nonparabolic models for the conduction band. The cyclotron mass is studied as a function of the Al concentrationxin the barrier for different magnetic fields. A discussion of the influence of nonparabolicity on thexdependence of the cyclotron mass and a comparison with previously reported experimental data are presented. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359540

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Transport positron‐atom elastic scattering cross sections have been computed for kinetic energies in the range 500–4000 eV. The phase shifts have been calculated by numerically solving the Dirac equation for a central electrostatic field up to a large radius in which the atomic potentials are negligible. Atomic potentials were that of Hartree–Fock forZ≤18 and of Dirac–Hartree–Fock–Slater forZ≳18. An analytical expression depending on three parameters, obtained by fitting the numerical results, is proposed for the energetic range examined to calculate transport cross sections for positron‐atom elastic scattering in the atomic number range 1–92. The accuracy of the given expression for energies lower than 500 eV and greater than 4000 eV has been discussed by comparison with other tabulations. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358697

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Formation of defects during Zn diffusion into undoped and semi‐insulating Fe‐doped InP single crystals at 700 °C was observed by transmission electron microscopy for various diffusion conditions. Agglomerates of predominantly perfect interstitial‐type dislocation loops, dislocations, and small indium precipitates inside voids are observed in the Zn‐diffused crystal region. In addition, large planar arrays of precipitates are formed by climbing dislocations. From these observations it is concluded that the incorporation of Zn on In sublattice sites creates a supersaturation of In self‐interstitials which is relieved by dislocation loop formation leading to a supersaturation of P vacancies and void formation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358698

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A technique forinsituobservation of chemical‐vapor deposition (CVD) is demonstrated. An environmental transmission electron microscope with 3.8 A˚ resolution was used for real‐time,insituobservation of Al CVD onto SiO2from trimethylamine alane (TMAA). Nominal TMAA pressures from 50 to 400 mTorr and substrate temperatures from 50 to 200 °C were investigated for deposition onto both TiCl4pretreated and untreated surfaces. For deposition onto untreated surfaces, low nucleation densities and polycrystalline, dendritelike growth were observed for all deposition temperatures with deposition commencing at about 150 °C. Deposition on TiCl4‐treated surfaces resulted in polycrystalline films with grain sizes of a few nm and lower‐temperature (100 °C) growth. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358699

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.359612

出版商:AIP    

年代:1995

数据来源: AIP