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Abstract
A finite-element programme has been developed to model strain relaxation in the case of epitaxial Si1− x Ge x /Si coherent quantum dots either with or without compositional inhomogeneities. The resulting elastic displacement fields are used to calculate the intensity of dynamical plan view TEM images of such quantum dots. Various types of linear or parabolic compositional inhomogeneities are studied. TEM images of quantum dots with such inhomogeneities are calculated as well as those of quantum dots with a homogeneous composition. They are then compared with experimental images. It is shown how the analysis of the main features of these experimental images (black/white lobes and moiré-like fringes) enables us to determine the conditions in which it is possible to distinguish quantum dots with a homogeneous composition from those with compositional inhomogeneity.
Acknowledgements
This work was partially supported by the French “Région Nord-Pas de Calais”, by the European FEDER (“Fonds Européen de Développement Régional”) and the “Action Concertée Nanosciences/Nanotechnologies”. Many thanks are due to Drs D. Bouchier and L.H. Nguyen (Institut d'Electronique Fondamentale, Orsay, France) for providing the SiGe/Si samples.