X-ray characterization of germanium nanoclusters in silica thin films

Ge nanoclusters in silica films were prepared either by electron beam evaporation of germanium and silica (PVD) or by evaporation and simultaneous ion bombardment (IBAD), both followed by post-deposition annealing. The two preparation methods are compared regarding the resulting cluster size and size distribution. The cluster size was calculated from the FWHM of different diffraction peaks. These results were compared for some selected films with high resolution X-ray diffraction (XRD) and transmission electron microscopy (TEM). Clusters from 20 to 300 إ were observed. A correlation between cluster size and the Ge concentration is seen. The concentration of Ge in the IBAD films depends on sputtering that is arrival rate (Ge/SiO2) dependent. The IBAD films showed smaller Ge cluster sizes and narrower size distributions than the PVD films.