Evolution of multiple-peak photoluminescence of Ge-doped silicon oxide nanoparticles upon thermal annealing

Photoluminescence (PL) properties of amorphous Si/Ge alloy oxide nanoparticles produced from Ge-doped silicon nanocrystals are studied at room temperature using the 266 nm (4.66 eV) laser line of a pulsed Nd:YAG laser as excitation source. Several radiative point defect centers contributing to the multiple PL are revealed by PL peak feature analysis and time-resolved PL measurements. The coexistence of nonbridging oxygen hole centers and oxygen-deficient centers is identified to be responsible for the PL properties. The evolution of the PL curves upon thermal annealing indicates a fluctuation of the defect state distribution in the oxide. Moreover, the PL spectra reveal the presence of Ge and Si nanocrystals formed at elevated temperature.