Characterization of ge nanocrystals in a-SiO2 synthesized by rapid thermal annealing

Abstract

We report the synthesis of nanocrystals of Ge embedded in a-SiO2 matrix by rapid thermal annealing (RTA). The films were deposited by rf-magnetron co-sputtering of Ge and SiO2 followed by RTA for 300 s. Raman studies indicate a transition of Ge from amorphous to nanocrystalline form when annealed between 700 to 800°C. The Raman spectra were analysed in terms of phonon confinement model and the estimated nanocrystal size was between 20 to 80 Å. A strong visible broad band photoluminescence was observed for the crystal size between 20 to 60 Å. The photoluminescence showed a blue shift with decrease in the nanocrystal size. The origin for the photoluminescence is discussed in terms of quantum confinement of excitons. © 1999 Elsevier Science B.V. All rights reserved.