摘要:

AbstractThis study is embedded in the broader context of reactive metal overlayers and passivation on GaAs. High resolution synchrotron‐radiation photoemission experiments for Ti coverages on Se‐reacted GaAs (110) surfaces show that, contrary to clean Ti‐reacted GaAs (110) interface, there is no initial disruption (submonolayer reaction) of the surface involving both Ga and As atoms during early stage of interface formation. However, a delayed Ti involved reaction appears at a trigger coverage of about 1 ML involving only As atoms from the prereacted AsSe interface configuration continued by Stranski‐Krastanov growth mode. A second reacted phase starts to form two GaTi involved configurations replacing GaSe bonds near a Ti coverage of 4 ML. The preferential chemical trapping of Ti by Se atoms is associated with a smaller interface thickness very likely<10 ML instead of 50 ML in the case of clean Ti/GaAs (110) interface caused by mo

ISSN:0232-1300    

DOI:10.1002/crat.2170320302

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170320303

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractEffect of neutron irradiation (E= 2 MeV, ϕ ≤ 1015n/cm2) and subsequent annealing (T≤ 700 °C,t= 30 min) on the intensity of the copper‐related peaked athvm =1.01 eV emission band inn‐type GaAs (n0= 2 × 1018cm−3) is studied. A strong irradiation‐induced increase of the above emission intensity was observed testifying about the irradiation‐stimulated growth in the concentration of copper‐related 1.01 eV radiative centres (CuGaVAspairs). A model is presented to e

ISSN:0232-1300    

DOI:10.1002/crat.2170320304

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractX‐ray powder diffraction data were obtained for Cu3In5Se9and Cu3Te9, which were found to crystallize in orthorhombic and tetragonal systems, respectively. The electrical resistivities and Hall mobilities of these compounds were investigated in the temperature range 35–475 K. Cu3In5Se9, was identified to ben‐type with a room temperature resistivity of 3 × 103Ω·cm which decreases with increasing temperature. ForT350 K onset of intrinsic conduction yielding a band gap energy of 0.99eV were detected. The neutral impurity scattering was found to dominate at low temperatures, while in the high temperature region thermally activated mobility was observed. Cu3In5Te9exhibitsp‐type conduction with a room temperature resistivity of 8.5 × 10−3Ω·cm decreasing sharply above 400 K and yielding an impurity ionization energy of 0.13 eV. The temperature dependence of mobility indicates the presence of lattice and ionized impuritiy scattering mechanisms above and below 160

ISSN:0232-1300    

DOI:10.1002/crat.2170320305

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractIn cholesteric liquid crystals the application of an electric field parallel to the helix axis can change the wavelength of selective reflection. For decreasing pitch of the studied mixtures, the colour shift becomes more stable against the field‐induced transformation of the initial Grandjean structure into a confocal texture. In compounds with a low crossover frequency, a field induced increase of the pitch was observed at the switching between low and high frequency fields. The investigations allow new conclusions on the origin of the colour shif

ISSN:0232-1300    

DOI:10.1002/crat.2170320306

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNdxY1‐xAl3(BO3)4(NYAB) single crystal was grown by the flux method using K2CO3MoO3as a solvent. By x‐ray projection topography, the defects on a (0001) slice of the NYAB crystal are investigated. It is found that the main grown‐in defects in NYAB crystal are growth bands, growth sector boundaries and inclusions. The formation of defects is discussed and methods to reduce the defects are p

ISSN:0232-1300    

DOI:10.1002/crat.2170320307

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe effect of the pulling rate and of the furnace configuration on the interface shape in semitransparent crystals grown by the vertical Bridgman method are studied by finite—element analysi

ISSN:0232-1300    

DOI:10.1002/crat.2170320308

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAl‐1 wt% Si and Al‐1 wt% Si‐0.1 wt% Zr–0.1 wt% Ti alloys were used to trace the effect of Zr and Ti additions on the behaviour of the steady state creep. After solid solution treatment specimens of both alloys were aged at 623, 673, 723 and 773 K and creep tests were performed at room temperature by applying stresses of 60.0, 62.4, 64.7 and 67.1 MPa. The results showed a sound stabilization effect of Zr and Ti on the ageing characterstics of binary Al‐1 wt% Si alloy. Values of the applied stress sensitivity parameter, m, obtained were in the range of (20–34) for AlSi alloy and (14–19) for AlSiZrTi alloy. Time to rupture was found to be strongly increased by Zr and Ti additions. The activation energies of the precipitation process involved were found to be 81.9 kJ/mole and 33.7 kJ/mole of the AlSi and AlSi

ISSN:0232-1300    

DOI:10.1002/crat.2170320309

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractA series of nickel‐molibdenum catalysts supported on alumina modified with sulfate and phosphate ions was studied. The studies involved texture evaluation measurements through N2adsorption isotherms. Besides, IR spectroscopic and derivatographic studies were carried out. Results of the studies enable us to conclude that modification of the alumina support with the above ions leads to a significant decrease in its surface area and pore volume. Modification does not result in a change of the type of pores of the support, but in the change of their size dimention. The pores present on the surface of the catalyst have the shape of “ink‐bottles”. Modification with phosphate ions improves the thermal stability of the catalyst, whereas sulfate ions present on the surface of the catalyst undergo decomposition upon heating of the sample. Phosphate ions inhibit formation of aluminum molybdate, and instead form polymeric layer structures of phosphate on the surface of catalysts. Sulfate ions occur in the form of surface aluminum

ISSN:0232-1300    

DOI:10.1002/crat.2170320310

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSingle crystals of solid solutions of tin sulphoselenide have been grown in the same ampoule. Specific conditions for growing single crystals of SnSSe have also been identified. A study of microstructures on the growth surfaces responds to the mechanism of growth of these crystals. The dependence of electrical resistivity, Hall mobility and carrier concentration with the values of the configuration parameter 2 has been studied.

ISSN:0232-1300    

DOI:10.1002/crat.2170320311

出版商:WILEY‐VCH Verlag    

年代:1997

数据来源: WILEY