Enhancement and stability of photoluminescence from Si nanocrystals embedded in a SiO2 matrix by H2-passivation

Si nanocrystals embedded in SiO2 (Si-NCs/SiO2) with efficient light emission were prepared by N2-annealing of amorphous SiOx (a-SiOx) and subsequent H2-passivation, and the effects of passivation on the photoluminescence (PL) from Si-NCs/SiO2 were studied. The H2-passivation was performed in a mixed gas of 5% H2 + 95% N2 at temperatures ranging from 400 to 700 °C for varied times, which is effective for passivating dangling bonds and enhancing luminescence. The PL intensity increases with passivation time, shortly followed by a saturation that depends on the passivation temperature. The H2-passivation also results in a red shift of PL spectra. The effects of H2-passivation show nearly complete reversibility as revealed by the emitted luminescence. Subsequent heating of the passivated samples in N2 has an effect of depassivation which regenerates dangling bonds and the regenerated dangling bonds can also be passivated. Si-NCs/SiO2 are found to exhibit stable behaviors in passivation and depassivation processes after three cycles of passivation and depassivation treatments.