摘要:

The weak-beam method of transmission electron microscopy has been applied to measure the dissociation width of superlattice dislocations in Ni3(Al,Ti) as a function of temperature. Dislocations in thin foils parallel to (111) and (010) planes were investigated. No significant variation of the distance between the unit dislocations which constitute the superlattice dislocation was found over the temperature range from 298 to around 950 K. The experimental observations are discussed in the framework of the model proposed by Brown. It is based on the transformation of geometrical antiphase boundaries (APBs) into APBs in their thermodynamic equilibrium configuration. The role of this APB-based model is examined with respect to the anomalous increase of the flow stress with increasing temperature.

ISSN:0950-0839    

DOI:10.1080/09500838908214769

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We discuss the results of an extended X-ray absorption fine-structure (EXAFS) study of chemical disorder in flash-evaporated nearly-stoichiometric amorphous Gap. The EXAFS spectra of the Kedges of both Ga and P are compared to similar data for crystalline Gap. The differences, which appear most clearly on the P edge, are analysed with a fitting procedure and are assigned to the presence of ‘wrong bonds’, namely bonds between like atoms, in the amorphous compound.

ISSN:0950-0839    

DOI:10.1080/09500838908214770

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We demonstrate the application of ultramicrotome techniques for the preparation of thin semiconductor interfaces in cross-section, for analysis by electron beam techniques. This is of significance for semiconductor device technology, since a specific area on a particular device may be examined in cross-section. High-resolution transmission electron microscopy studies of twinned structures at the interface of a 1.2 μm metal-organic chemical vapour deposited HgCdTe epilayer on {100} GaAs are reported. {100} epitaxial growth starts to dominate about 40 nm from the interface, and continues to the top surface of the epilayer. Energy-dispersive X-ray analysis shows that the mercury concentration within the epilayer increases as the interface is approached. No evidence of diffusion into the GaAs substrate was obtained.

ISSN:0950-0839    

DOI:10.1080/09500838908214771

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A thin foil of pure titanium has been implanted with increasing fluences of B+ions and the structural changes have been observed continuously viain situtransmission electron microscopy. A textured film of the orthorhombic TiB compound was formed instead of the hexagonal TiB2phase observed by other authors.

ISSN:0950-0839    

DOI:10.1080/09500838908214772

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A method of deriving the shape of pair potentials describing both the long- and short-wavelength behaviour of b.c.c. metals within the Finnis-Sinclair many-body-potential model is described. The method guarantees a fit to both the elastic constants and zone-boundary vibrational frequencies of b.c.c. metals using the five nearest-neighbour shells in the b.c.c. structure. The application of the method to niobium is briefly discussed and compared with previous work.

ISSN:0950-0839    

DOI:10.1080/09500838908214773

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The hydrostatic pressure dependence of the photoluminescence (PL) intensity from hydrogenated amorphous silicon has been measured in a diamond anvil cell at 80 K. The PL intensity is not quenched significantly by pressures up to ∼90 kbar, but in the pressure range ∼90–130 kbar quenching is observed. The luminescence displays a red shift of 1.9±0.1 meV kbar−1, with a hysteresis of ∼35meV at the highest pressures.

ISSN:0950-0839    

DOI:10.1080/09500838908214774

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Aluminium has been introduced into a-Sic: H by co-sputtering of silicon-aluminium in a gas mixture of methane-argon and its effect on the optical, electrical and opto-electronic properties of the films investigated. In the range of fractional aluminium content z up 10−2, the photoconductivity was maintained without a significant change in the optical band gap. A high value of photosensitivity (> 106) was obtained in the range of z between 10−4and 10−3. On increasing z above 10−2, the photoconductivity is quenched, being accompanied by a decrease in the optical band gap as well as by an increase in the dark d.c. conductivity.

ISSN:0950-0839    

DOI:10.1080/09500838908214775

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor