Raman and photoluminescence properties of Ge nanocrystals in silicon oxide matrix

Abstract

Ge nanocrystals (nc-Ge) embedded in silicon oxide thin films have been fabricated using rf magnetron co-sputtering deposition and post-growth thermal annealing method. Raman scattering and photoluminscence (PL) measurements have been used to characterize their crystallization and light emission properties. The Ge crystallinity and nanocrystal size obtained using a three-peak fitting method based on a phonon confinement model have been found to increase with the increase of annealing temperature. The observed blue photoluminescence band located at ∼3.1 eV and a weaker band at ∼2.4 eV under the excitation of 325 nm laser did not show significant size dependence while their relative intensities were related to the addition of H 2 or O 2 into the sputtering ambient. The photoluminescence mechanism is discussed.