摘要:

AbstractTransparente CdAl2S4‐ und CdAl2Se4‐Einkristalle wurden durch chemischen Transport über die Gasphase in Größn bis zu 15 × 4 × 1 mm3(CdAl2S4) bzw. 10 mm Kantenlänge (CdAl2Se4) gezüchtet. Die Stöchiometrie der Kristalle wurde mittels Elektronenstrahl‐Mikrosonde überprüft. Strukturelle Untersuchungen nach der Rietveld‐Methode lieferten eine gute Übereinstimmung der gefundenen mit bekannten Strukturdaten. Aus Transmissions‐ und Reflektionsmessungen wurde der Bandabstand unter Annahme einea direkten Halbleiters bestimmt zu:Eg=3.82eV (RT),Eg= 3.94 eV (85 K) für CdAl2S4undEg= 2.95 eV (RT),Eg= 3.07

ISSN:0232-1300    

DOI:10.1002/crat.2170320202

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170320203

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAn attempt to identify the polarity of (0001) polar surface of GaN bulk single crystals grown by high nitrogen pressure solution method has been made using Auger electron spectroscopy (AES). AES concentration depth profiles of the top layer in (0001) direction starting from both (0001) faces of the sample have been measured. Distinct difference in the Ga concentration at the sample surface of both faces has been observed. The dependence of Ga eoncentration on depth is also different for both faces of the sample.

ISSN:0232-1300    

DOI:10.1002/crat.2170320204

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170320205

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCuxAg1–xGaS2large‐scale blocks were obtained by two‐temperature synthesis method with the following crystallization of the melt. It was established, that crystal lattice parameters are changed according with Vegard's law, and microhardness have an extremum on the base DTA measurements state diagram of AgGaS2CuGaS2system was built up. The composition dependence of band gap has nonlinear be

ISSN:0232-1300    

DOI:10.1002/crat.2170320206

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe wafer processing of Indium Phosphide (InP) is so important that it is getting more and more attentions. Lapping is a basic step just following the ingot cutting. In this paper, the influences of various processing parameters on the lapped wafer quality and lapping rate have been checked, the double‐crystal X‐ray diffraction results about lapped wafers also were presented here. According to the experimental results, the optimum lapping conditions have been obtai

ISSN:0232-1300    

DOI:10.1002/crat.2170320207

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPb‐doped Bi2Se3crystals were prepared from starting elements Bi, Se and Pb of 5N purity in the concentration intervalcpb= 0 – 4 × 1025Pb atoms m−3by a modified Bridgman method. The measured values of the transmittance and reflectance were used to determine the dependence of the absorption coefficientKon the photon energy for crystals with various values ofcpb and to prove the shift of the short‐wavelength absorption edge withcpb. On the basis of the assumption of the validity of the “single valley” model, which can describe the lowest conductivity band of Bi2Se3, and using the values of the freecarrier effective mass in the directions perpendicular and parallel to the trigonal axiscwe determined the value of the reduced Fermi energy η 300 K for crystals with various values ofcpb. Using the value of η, we calculated the dependence of the Seebeck coefficient oncpb and compared it with the experimentally determined values. The comparison has shown that the increasing content of Pb atoms in the Bi2Se3lattice leads to a suppression of the role of the mechanism of scattering by ionised impurities; at higher concentrations of Pb in the crystal the mechanism of scattering of free carriers by acoustic phonons becomes dominant. Further, the ideas on the nature of the point defects in the Bi2Se3(Pb) crystals are presented and the “anomalous” dependence of the free‐electron concentration oncpb is qualita

ISSN:0232-1300    

DOI:10.1002/crat.2170320208

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThermodynamic conditions and energy considerations for the formation of hollow cores at the emergence points of monolayer cleavage steps associated with screw dislocations on the cleaved {100} faces of LAP single crystals are discussed. Analysis of the formation of hollow cores and the change of the curvature of steps in the vicinity of their origins reveals that dislocations responsible for the origin of hollow cores have stress fields due to trapped mother liquor of different supersaturations. The results also show that (1) the radius of a hollow core is inversely proportional to the one‐third power of the interface supersaturation while the volume of hollow corés increases exponentially with their radius, and that (2) the strain energy associated with a dislocation is responsible for the formation of an equilibrium hollow core of a particular depth at the origins of cleavage steps associated with dislocatio

ISSN:0232-1300    

DOI:10.1002/crat.2170320209

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNew tail‐to‐tail twins with alkyl or perfluorinated spacers were synthesized. The mesomorphic properties were studied by polarizing microscopy and X‐ray diffraction measurements. It was found that the smectic C phase is a Sc2phase with alternating tilt and an intercalated structure. The alternating tilt gives rise to an unusual schlieren texture which exhibits not only singularities with the strengths= ±1 but also those withs= ±1/2 and

ISSN:0232-1300    

DOI:10.1002/crat.2170320210

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA novel method, molecular vibration approach is presented and used to evaluate polarizabilities, polarizability anisotropies and diamagnetic susceptabilities of Azo Benzene liquid crystal compound. In this approach vibrational frequencies are used to calculate the force constants, mean amplitude of vibrations and bond polarizabilities. In addition, the variation of order parameter with temperature is also studied. The results are compared and discussed with the literature values.

ISSN:0232-1300    

DOI:10.1002/crat.2170320211

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY