EFFECT OF ANNEALING AND H-2 PASSIVATION ON THE PHOTOLUMINESCENCE OF SI NANOCRYSTALS IN SIO2

Silicon nanocrystals have been synthesized in an SiO2 matrix using Si ion implantation. Si implantations have been performed at 35 keV with doses from I x 10(16) cm(-2) to 7 x 10(16) cm(-2), corresponding to pe ak excess concentrations of 3 at.% to 17 at.%. The samples have been a nnealed in vacuum at various temperatures to obtain Si nanoclusters of different sizes. Photoluminescence (PL) experiments show a distinct s hift of the spectra towards lower energies and a decrease in intensity with increasing a annealing temperature between 700 degrees C and 900 degrees C for doses higher than 5 x 10(16) cm(-2). We also observe fo r these samples that the peak position appears at lower energy for hig her doses, Additional annealing in H-2/N-2 results in a strong increas e of the PL intensity which is attributed to the passivation of defect s. Annealing the samples again in vacuum leads to a reproduction of th e former PL spectra showing the reversibility of the passivation, Thes e experiments are in qualitative agreement with the quantum confinemen t model and in contradiction to recent observations made on Ge nanocry stals in a SiO2 matrix (K.S. Min et al., Appl. Phys. Lett., submitted) .