Microstructural and photoluminescence studies of germanium nanocrystals in amorphous silicon oxide films

Abstract

Ge nanocrystal growth in amorphous silicon oxide film was studied using the transmission electron microscopy and x-ray photoelectron spectroscopy techniques. The as-sputtered sample contained mainly GeO2 and Ge suboxides. GeO2 and/or suboxides dissociate when rapid thermal annealed and provide Ge for nanocrystal formation. Nanocrystals of similar size (∼60 Å in diameter) were obtained when annealed at 800 °C. Nanocrystals with diameters of 200–280 Å consisting of multiple twin structures near the Si–SiO2 interface were observed when annealed at 1000 °C. The twin structure was attributed to the enhanced diffusion of Ge at 1000 °C and the short annealing time. Our photoluminescence (PL) results show that the best PL response was obtained with samples that exhibit uniform nanocrystal size.