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X-ray diffuse scattering from a 17-fold InGaAs/GaAs quantum dot (QD) multilayer grown by an advanced molecular beam epitaxy process was investigated. The QDs in each layer form extended chains that are oriented along the [110] planar direction. A prominent three-dimensional satellite structure in the x-ray diffuse scattering is found, which is caused by a strong lateral chain-chain correlation and vertical correlation of the lateral chain positions in the multilayer. In contrast, the dot-dot correlation within the chains are comparatively small. Numerical x-ray scattering simulations have been carried out. A comparison with corresponding experimental intensity patterns provides information on the QD size and QD spatial distribution.

The plastic relaxation of SiGe/Si is closely related to the nucleation of misfit dislocations at early stages. We have investigated the very early stages at annealing temperatures ranging from 520°C to 670°C by means of x-ray topography (XRT), atomic force microscopy (AFM) and transmission electron microscopy. At misfit dislocation densities within the range accessible by XRT, i.e. up to about 1000 cm−1, dislocations bundles predominate. This is verified by AFM and is explained by heterogeneous nucleation. The fewer the dislocations that are contained within dislocation bundles the rarer the blocking and cross slip that are observed. It is demonstrated that laser heating increases the number of nucleation centres drastically and is well suited to induce nucleation at selected sites. Furthermore, these nucleation centres provide dislocation bundles containing only a few dislocations. In contrast to this, implantation can produce defects that stop dislocation propagation quite effectively at the comparatively low temperatures used in our experiments.

We have investigated the x-ray intensity distribution around 220 reciprocal lattice point in case of grazing incidence diffraction at SiGe nanoscale free-standing islands grown on Si(001) substrate by LPE. Experiments and computer simulations based on the distorted wave Born approximation utilizing the results of elasticity theory obtained by FEM modelling have been carried out. The data reveal fine structure in the distribution of scattered radiation with well-pronounced maxima and complicated fringe pattern. Explanation of the observed diffraction phenomena in their relation to structure and morphology of the island is given. An optimal island model including its shape, size and Ge spatial distribution was elaborated.

Highly regular islands of strained Si1-xGex have been grown on Si (001) by liquid phase epitaxy (LPE). The islands themselves are {111}-faceted truncated pyramids with a narrow base-width size distribution and coherent behaviour. In this study we report on the state of lateral ordering within a single layer of Si1-xGex islands. Grazing incidence small-angle x-ray scattering (GISAXS) was used to investigate the ordering as a function of island coverage. At very low island coverage the array behaves like a two-dimensional liquid exhibiting an increased number of island dimers which orient along the island base diagonal 100. On increasing the coverage these dimers develop into extended chains of islands oriented along 100. At high coverage there is strong ordering along both the 100 and the 110 directions. The self-organised ordering can be explained by two possible mechanisms: (i) that the observed ordering is driven by the anisotropy of the elastic constants where short-range order along the soft 100 directions is expected, and (ii) that there is an underlying two-dimensional ripple pattern in the wetting layer aligned along the 100 directions. At later stages of growth this pattern transforms into pseudomorphic islands.

Characteristics of the interface roughness in a low-pressure organometallic vapour phase epitaxy (LPOMVPE) grown AlAs/GaAs multilayer are studied by grazing-incidence x-ray scattering. Quantitative results are obtained by comparing experimental and theoretically calculated diffuse scattering maps. These corroborate with the features resolved by atomic force microscopy. The observed morphological features are discussed in the following sections.

Threading dislocations in gallium arsenide and point defects in silicon were observed for the first time by X-ray topography under grazing-incidence diffraction conditions. A new type of contrast on polished surfaces has been resolved for single crystals with defects. The characteristics of grazing-incidence diffraction topography are discussed.

By means of X-ray double-crystal topography we have investigated silicon-on-insulator lamellae grown by liquid-phase epitaxy upon thermally oxidized silicon. The majority of the lamellae were free of extended defects. It is shown that the topographic contrasts of these lamellae are mainly due to vertical stress exerted by the lamellae onto the substrate. This is surprising because the aspect ratio (thickness/lateral dimension) is of the order of 10-2. Our first calculations lead us to estimate the stress to be around 10 N cm-2. A simple model, which may be assumed to apply in general for crystal growth on amorphous substrates, is described here. It relates the stress to an adhesive force, which acts during growth.