Ion beam synthesis of germanium nanostructures

Si and Ge nanocrystals embedded in SiO2 have attracted much attention due to their possible application in integrated optoelectronic devices. Ion beam mixing of Ge film into fused silica to form Ge nanoparticles is one of the possible methods to controllably produce embedded nanoclusters. In this work, Ge nanocrystals in fused silica were formed by defect induced nucleation and ion beam mixing. In our experiment, we have created defects in fused silica using 200 keV Ar ions with different fluences ranging from 1 × 1015 to 2 × 1016 ions/cm2 (pre-mixing irradiation). Ge film (20 nm) was then deposited on it and ion beam mixed using 230 keV Ar ions at a fluence of 2 × 1016 ions /cm2. The Ge–SiO2 composite films were characterized using UV–visible and Micro-Raman spectroscopy. UV–visible spectra showed variation in absorption band gap with ion beam fluence used for pre-mixing irradiation. Micro-Raman spectra showed formation of Ge nanoparticles in SiO2.