摘要:

Electron energy-loss spectroscopy measurements have been made on amorphous diamond-like carbon films produced by condensing the plasma stream from a filtered vacuum arc. The results are compared with spectra from diamond, graphitized carbon and amorphous carbon. Although the energy-loss spectra reveal the presence of a small quantity of sp2-bonded material in the diamond-like film, the high plasmon frequency and shape of the K-edge show that the material is essentially an amorphous form of diamond. The fraction of sp2- bonded carbon was quantified and found to be of the order of 15%. It was not possible to determine if the sp2carbon was on the surface or throughout the bulk.

ISSN:0950-0839    

DOI:10.1080/09500838808214715

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The thermoelastic martensitic transformation in shape-memory alloys is studied thermodynamically. Calorimetric experiments on the Cu─Zn─A1 alloy system reveal that the transformation takes place with a practically negligible entropy production. The usual hysteretic subloop behaviour during partial cycling is obtained for the first time by calorimetry. An analysis of the measurements gives the quantitative behaviour of elastic and dissipative energies with the volume fraction of martensite.

ISSN:0950-0839    

DOI:10.1080/09500838808214716

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The radius of curvature of dislocations in the thermally activated regime of glide, and in a non-uniform stress field, is derived from two characteristic times related to kink velocity. The result is compared to experimental values of the radius of curvature at the corner of stress-induced dislocation loops in silicon.

ISSN:0950-0839    

DOI:10.1080/09500838808214717

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

It is shown that the mechanism of high-temperature superconductivity in oxygen-deficient perovskites, based on a cooperative Jahn-Teller effect for Cu2+ions, allows the dependence of the critical temperatureTcon oxygen content to be calculated. This dependence qualitatively accounts for the experimental data in the case of YBa2Cu3O2and the maximum predicted forTcis consistent with that deduced from structural data.

ISSN:0950-0839    

DOI:10.1080/09500838808214718

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We have determined the electric transport properties in the pre- and post-breakdown regime of p-germanium at low temperatures from conductivity and Hall-effect measurements. The breakdown mechanism is demonstrated to involve a mobility which depends sensitively upon the density of the mobile charge carriers.

ISSN:0950-0839    

DOI:10.1080/09500838808214719

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The temperature and time dependence of the d.c. conductivity of undoped hydrogenated amorphous silicon is presented. Measurements of the electronic transport are reported, with particular emphasis on the effects of annealing and cooling the samples. Two regimes of behaviour are observed. When samples are rapidly cooled from 200°C below a temperatureTE∼145°C a non-equilibrium dark conductivity, higher than that corresponding to slow cooling, is observed. The electronic and atomic structure then slowly relax and the time dependence of the excess conductivity is well described by a stretched exponential function. The second regime aboveTEcorresponds to a relaxation time short compared to experimental times and the conductivity is independent of which order the annealing temperature is chosen. Thus the thermal equilibrium processes observed in undoped samples are qualitatively very similar to those observed in doped samples as recently reported in the literature.

ISSN:0950-0839    

DOI:10.1080/09500838808214720

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0950-0839    

DOI:10.1080/09500838808214721

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor