Luminescent Ge nanocrystallites embedded in a-SiO2 films

Abstract

The luminescent nanocrystal Ge embedded in a-SiO2 matrix was prepared by thermal oxidation of a-Si1-xGex:H films under conventional conditions. It was found that nc-Ge were formed through the selective oxidation of Si in a-GexSi1-x:H alloys and precipitation of Ge during oxidation. The average size of nc-Ge changed from 4 nm to 6 nm with the various conditions and Ge contents. Visible photoluminescence with peak energy 2.2 eV was observed from the oxidized samples where the nc-Ge have an average size of 4 nm. In order to control the size distribution of nc-Ge, we used multilayer films of a-Si:H/a-Si1-xGex:H instead of unlayered a-Si1-xGex:H alloy films to prepare nc-Ge embedded in SiO2 matrix. We found that the size of nc-Ge in perpendicular direction can be well confined by the SiO2 sublayers simultaneously formed.