Novel technologies often require the implementation of novel materials or a new way of combining known materials. In this research topic, the electron microscopy group collaborates with other reseach groups on new semiconductor heterostructures. One sub-project concerns the development of an advanced X-ray detector based on Ge pillars grown on patterned silicon. Due to the large lattice mismatch between Si and Ge, the Ge is heavily strained due to the epitaxial growth. The strain is partially plastically relaxed by the formation of dislocations and the formation of other structural defects, like e.g. stacking faults. Characterization of these defects  is crucual for advancing the understanding of their occurance as a function of growth conditions and for developping the structure-property relation of the final device.