HREM CONTRAST INTERPRETATION OF PSEUDO-SYMMETRICAL STRUCTURE REGIONS IN NANOCRYSTALLINE GERMANIUM

The atomic structure of nanocrystalline particles formed by vapour dep osition and subsequent annealing of amorphous thin films of germanium is studied by high resolution electron microscopy, image processing, a nd image simulation. The HREM images reveal a highly varied multiply t winned structure. In some regions of adjacent twins contrast features are detected that show pseudo-symmetric linear and circular superstruc tures of local non-crystallographic symmetry. These contrast features are caused by an overlapping of twin lamellae as is demonstrated by co ntrast simulations. The simulation procedure is carried out for differ ent models of superimposed twins.