Light emitting germanium and silicon nanoislands grown by RF magnetron sputtering

The role of annealing temperature on the structural and optical properties of Ge and Si nanoislands deposited on Si(100) grown by radio frequency magnetron sputtering technique are studied. Atomic force microscopy confirmed the formation of Si and Ge nanoislands with estimated sizes lower than 100 nm and 45 nm respectively. The room temperature photoluminescence spectra for Si revealed an emission peak at 2.53 eV which is attributed to the formation of Si nanoislands whereas the observed strong luminescence peak at 3.22 eV for Ge nanoislands is attributed to the quantum size effect. A shift in the PL peak is observed upon annealing which is due to effect of quantum confinement and surface passivation by oxygen. The thermal annealing at 600 0C is found to play an important role in controlling the shape, number density, root mean square roughness and the energy shift of the luminescence band for both Si and Ge nanoislands. The influence of annealing on growth morphology for Ge nanoislands is appeared to be stronger than Si. The growth mechanism and the luminescence is analyzed and compared with other observations