Si nanocrystals embedded in SiO2 (Si-NCs/SiO2) with efficient light emission were prepared by N-2-annealing of amorphous SiOx (a-SiOx) and subsequent H-2-passivation, and the effects of passivationon the photoluminescence (PL) from Si-NCs/SiO2 were studied. The H-2-passivation was performed in a mixed gas of 5% H-2 + 95% N-2 at temperatures ranging from 400 to 700 degrees 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 H-2-passivation also results in a red shift of PL spectra. The effects of H-2-passivation show nearly complete reversibility as revealed by the emitted luminescence. Subsequent heating of the passivated samples in N-2 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. (C) 2014 Elsevier B.V. All rights reserved.