摘要:

Two samples of nominal 20-period Ge0.20Si0.80(5nm)/Si(25nm) and Ge0.5Si0-5(5nm)/Si(25nm) strained-layer superlattices (SLSs) were studied by the double-crystal X-ray diffraction method. It is convenient to define the perpendicular strains relative to the average crystal. Computer simulations of the rocking curves were performed using a kinematical step model. An excellent agreement between the measured and simulated satellite patterns is achieved. The dependence of the sensitivity of the rocking curves to the structural parameters of the SLS, such as the alloying concentration x and the layer thicknesses and theLcomponent of the reflectiong = (HKL), are clearly demonstrated.

ISSN:0950-0839    

DOI:10.1080/09500839308240484

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Planar decagonal-phase precipitates were observed in icosahedral Al—Pd—Mn quasicrystals and analysed by conventional and high-resolution transmission electron microscopy, Z-contrast imaging, electron-energy-loss spectroscopy and energy-dispersive X-ray analysis. The habit plane normal vector is parallel to the tenfold axis of the decagonal phase, which in turn is parallel to a fivefold direction of the quasicrystalline matrix. At the periphery *of the precipitates, dislocation-like structures occur. For the first time a complete six-dimensional analysis of the direction of the strain field vectors was achieved.

ISSN:0950-0839    

DOI:10.1080/09500839308240485

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The structures of thin films of RbAg4I5and CsAg4Br3-xI2+x, vacuum deposited on thin carbon supports, were investigated in a scanning transmission electron microscope. It has been found that a phase with a high ionic conductivity (solid electrolyte) formed in annealed films is very sensitive to electron irradiation. The use of a focused electron beam is demonstrated to produce directly features in films of the solid electrolytes.

ISSN:0950-0839    

DOI:10.1080/09500839308240486

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The decagonal phase of compositions Al68Cu11Co21and Al69Cu8Co23was studied by transmission and scanning electron microscopy. The electron diffraction patterns exhibited sharp reflections at positions in reciprocal space where, at higher Cu contents, only very weak diffuse intensity occurs. This is discussed in terms of superlattice ordering in the decagonal phase.

ISSN:0950-0839    

DOI:10.1080/09500839308240487

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Platelets of the Al—Pd—Mn decagonal phase have been observed to grow in epitaxy on the icosahedral modification of the same system. A resulting strain field in the icosahedral phase has been characterized using high-resolution electron microscopy. It appears that one fivefold axis is preserved, in coincidence with the tenfold axis of the decagonal phase. In the particular case of a thin icosahedral-phase domain squeezed in between two decagonal-phase platelets, the strain field can be qualitatively analysed in terms of combined phason–phonon strain fields.

ISSN:0950-0839    

DOI:10.1080/09500839308240488

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Structural transformations resulting from phason instabilities in icosahedral Al–Cu–Fe have been studied by powder X-ray diffraction. Three approximant phases, the modulated icosahedral phase and a state with substantial phason disorder are located in the phase diagram. Diffraction scans of the transformations are modelled using a projection of a distorted cubic six-dimensional lattice.

ISSN:0950-0839    

DOI:10.1080/09500839308240489

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

By using a high-temperature deformation method, two kinds of defect have been introduced into the Al70Co15Ni15decagonal phase. They are firstly high–density stacking faults with fault planes perpendicular to the tenfold axis, and displacement vectors R lying in the fault planes and parallel to a twofold axis A2D and secondly high–density dislocations with Burgers vectors parallel to the tenfold axis. Some dislocations exist as dislocation pairs. On the basis of experimental observations we have made the first estimate of the antiphase–boundary energy of the ordered Al70Co15Ni15decagonal phase (about 30erg cm–2) and explored the microscopic mechanism of high-temperature deformation of the decagonal quasicrystal.

ISSN:0950-0839    

DOI:10.1080/09500839308240490

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We have found that a misfit dislocation which moves within a slightly strained layer of Ga0·5ln0·5P with atomic ordering on {1T1} planes leaves an observable track in the form of an antiphase domain boundary. Here we describe our observations and discuss the possibility of using this material as a model system for the investigation of strain relaxation mechanisms.

ISSN:0950-0839    

DOI:10.1080/09500839308240491

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor