Modification of ge structural-morphological properties in multi-layered nanoperiodic Al$_{2}$O$_{3}$/Ge structure with intermediate Si layers

Multi-layered nanosized Al$_{2}$O$_{3}$/Ge/Si structures manufactured by electron-beam evaporation and annealed at a temperature within the range 700–900$^\circ$C are examined using transmission electron microscopy, Raman spectroscopy and X-ray diffraction techniques. The periodic structure with a good layer planarity is confirmed to retain after heat treatment up to 900$^\circ$C. At an annealing temperature above 700$^\circ$C, nanocrystallites with a bimodal size distribution start to form within initially amorphous Ge layers, the mean size of small crystallites being determined by Ge layer thickness and annealing temperature. An essential loss of Ge from multi-layered structure after 900$^\circ$C anneal and development of Ge$_{1-x}$Si$_x$ solid solution with $x$ up to 0.07 in the nanocrystallites is revealed.