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Anomalous x-ray diffraction has been employed to study hetero-epitaxially grown nanostructures. After the theoretical treatment of kinematic diffraction from epitaxial systems a detailed analytical solution is developed for crystal structures with more than one atom in the unit cell. It is applied to the scattering from thin films and 2D-layered structures. Effects of interferences between the structure amplitudes of different materials are demonstrated in order to find the optimum x-ray wavelength to discriminate between the different contributions. X-ray experiments were carried out over a wide energy range, reaching down to 2300 eV. This opens up the possibility to exploit strong resonance effects in one of the compounds, which is subsequently almost completely suppressed. In the system of the IV-VI semiconductors this is applied to multilayers and 3D-ordered quantum dot superlattices grown via self-organization. The long wavelength of the low energy x-ray beam together with the resonant effects enables an interdiffusion measurement in lead-europium chalcogenide multilayers down to a resolution with monolayer accuracy. Furthermore, the exploitation of the anomalous scattering technique leads to discovery of internal facets in multilayered quantum dot structures. To extend the study on the composition in quantum dots to the silicon-germanium system, a study at high momentum transfers is performed. Having a higher strain resolution and a significantly enhanced anomalous effect, this method is used to reconstruct the strain and interdiffusion profile in SiGe islands grown on Si. It is shown, that through deposition of Ge at 600 C, islands with a Ge content of up to 80 % are achieved that have a well defined interface to the substrate of pure Si. The independent measurement of composition and strain supplies a direct link to the elastic energy and its gradients inside the nano-crystal.
