On the origin of visible photoluminescence in nanometer-size Ge crystallites

Abstract
We have studied the origin of visible photoluminescence of Ge nanocrystals in SiOZ glassymatrix. Spectroscopic analyses of Ge nanocrystals indicate that the room-temperaturephotoluminescence comes from Ge nanocrystals of diameter of 4 nm or less. High-resolutionelectron microscopic studies imply that the structure of Ge nanocrystals of diameter <4 nmdiffers from the diamond structure. These data suggest that new nanostructure crystalline Gehaving a character of direct optical transition exhibits the visible photoluminescence