摘要:

Dislocation structure and planar faults have been examined in MoSi2single crystals deformed at high temperatures. Pure stacking faults were found in a crystal deformed at 900°C. The formation of the stacking fault is closely related to the phase stability of the C11band C40 ordered structures. Profuse stacking faults with increasing deformation temperature assist the ductility improvement of the MoSi2above about 1200°C. The critical resolved shear stress for {110}(331) and {013}(331) slip is determined in the temperature range 1000 to 1500°C.

ISSN:0950-0839    

DOI:10.1080/09500838908206338

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Transmission electron microscope observations have been made of dislocations in Ga0·7Al0·3As after indentation of (001) surfaces at room temperature. Using two-beam imaging, in bright-field and weak-beam imaging, dissociated dislocations with extended stacking faults were observed both in the [110] and [110] directions. This is different from GaAs in which dissociated dislocations are seen in only one of these directions. These results are compared with published work on indented GaAs and considered in the light of possible mechanisms.

ISSN:0950-0839    

DOI:10.1080/09500838908206339

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The topotaxial phase transition, which is induced by gold-ion bombardment, from α-Al2O3, to γ-Al2O3has been observed. The formation of γ-Al2O3has been confirmed by transmission electron microscopy and X-ray diffraction. Between the γ-Al2O3phase and original matrix structure of α-Al2O3there is a topotaxial relation of (11l)γ//(0001)α and [110]γ//[0001]α, but the matrix is amorphous. We discuss the crystal structure of the γ-Al2O3phase and a mechanism for the topotaxial phase transition with the amorphous matrix.

ISSN:0950-0839    

DOI:10.1080/09500838908206340

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Starting from variablep-vectors half-stars which verify Hadwiger's theorem, the cut-projection method is used here. The strip of projection is projected on a rotatory subspace and a variable tiling is obtained. Two outstanding examples are developed. The first, a continuous evolution from a two-dimensional octagonal quasilattice to two square lattices 45° rotated in between. The second is a continuous evolution from a three-dimensional Penrose tiling to an f.c.c. vertex lattice. Physical applications to quasicrystal-crystal transitions are pointed out.

ISSN:0950-0839    

DOI:10.1080/09500838908206341

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Anodic alumina films prepared in phosphoric, oxalic, sulphuric and chromic acids have been examined using magic-angle spinning nuclear magnetic resonance. Whilst only hexacoordinated aluminium is observed in films formed in chromic acid, tetra-, penta- and hexacoordination is observed in films formed in oxalic and sulphuric acid and tetra- and pentacoordination in the film formed in phosphoric acid. The data generally suggest an inhomogeneous film material with aluminium present both within microcrystalline and within more disordered film regions. The variation of aluminium coordination appears to be related to the presence of OH within the alumina material, with an increase of anodizing temperature favouring the development of hexacoordination.

ISSN:0950-0839    

DOI:10.1080/09500838908206342

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The drift mobility in a-Si p+–i–n+junctions under forward bias has been studied by the voltage pulse technique as a function of d.c. bias. This technique shows a dependence of the drift mobility on d.c. voltage and forward bias current. These results do not agree with recent laser-induced time of flight (TOF) measurements by Goldie, Le Comber and Spear. The voltage pulse technique has been criticised by Goldieet al.as giving incorrect results owing to an increase in capacitance under forward bias. In this Letter we consider more carefully the question of theRCtime constant under forward bias conditions and find that C does not change. Both the voltage pulse and laser-induced TOF techniques employed under forward bias are discussed in an attempt to reconcile the different results.

ISSN:0950-0839    

DOI:10.1080/09500838908206343

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Cathodoluminescence of various semiconducting materials with different surface treatments has been investigated as a function of election beam voltage at low injection levels. A correlation was found between the surface recombination velocity and beam voltage at which the cathodoluminescence is a maximum.

ISSN:0950-0839    

DOI:10.1080/09500838908206344

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor