Growth of Ge Microcrystals in SiO2 Thin Film Matrices: A Raman and Electron Microscopic Study

Abstract

The growth of Ge microcrystals in SiO₂-Ge mixture films prepared by an rf co-sputtering method was studied by Raman spectroscopy and electron microscopy. It was found that in the as-deposited films, Ge clusters about 2 nm in diameter are embedded in SiO₂ matrices and they are grown to Ge microcrystals by thermal annealing. It is shown that annealing at 800°C is necessary to prepare well-grown microcrystalline samples. The microcrystalline size dependence of the Raman spectrum was investigated. The increase in the linewidth observed with decreasing the size can be well explained by the phonon confinement theory, while the downward shift of the peak frequency predicted from the theory was not observed, presumably due to the stress caused by SiO₂ matrices.