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We built the honeycomb networks of misfit dislocations by combining angular dislocations. Two different models of the disorder in the dislocation network are explored, the random shifts of nodes and random sources of distortion. The displacement fields of disturbed dislocation networks are used to simulate the X-ray diffraction patterns by Monte Carlo method. We find that substantial disorder is needed for random shifts to be experimentally observable as diffuse scattering. The model of random distortion sources produces comparable diffuse scattering with the dislocation network looking closer to the initial perfect structure. The diffraction patterns due to distorted honeycomb dislocation networks are compared with the ones due to triangular networks of straight dislocations. The disorder parameters of the latter networks can be chosen to produce diffraction patterns similar to the former.

""We report on the experimental and theoretical investigation of the relaxation in Ge-rich SiGe\\\/Ge\\\/Si heterostructures. The experimental x-ray diffraction data are interpreted with the help of a model including both edge and 60 degrees misfit dislocations in the calculated x-ray scattering intensity. Our results show that highly positionally correlated edge dislocations dominate in the relaxation of the compressive strain at the Ge\\\/Si interface, while a smaller tensile strain at the SiGe\\\/Ge interfaces released by uncorrelated\\\/little correlated 60 degrees dislocations.""

X-ray diffraction from films consisting of layers with different thicknesses, structures and chemical contents is analysed. The disorder is described by probabilities for different sequences of layers. Closed analytical expressions for the diffracted X-ray intensity are obtained when the layers form a stationary Markov chain. The proposed model is applied to the diffraction data from epitaxial sodium bismuth titanate thin films with Aurivillius structure possessing such one-dimensional disorder. In this case, the disorder is caused by a random stacking of three and four perovskite units separated by bismuth oxide interlayers. The results of analytical calculations are in good agreement with the experimental data and indicate that the incorporation of sodium in the Bi(4)Ti(3)O(12) phase causes the formation of a fourth perovskite unit.

cited By 13; International audience; Densities of a- and a+c-type threading dislocations for a series of GaN films grown in different modes by metalorganic vapor phase epitaxy are determined from the x-ray diffraction profiles in skew geometry. The reciprocal space maps are also studied. Theory of x-ray scattering from crystals with dislocations is extended in order to take into account contribution from both threading and misfit dislocations. The broadening of the reciprocal space maps along the surface normal and the rotation of the intensity distribution ellipse is attributed to misfit dislocations at the interface. We find that the presence of a sharp AlN/GaN interface leads to an ordering of misfit dislocations and reduces strain inhomogeneity in GaN films.