Saturation of photoluminescence intensity from Si nanocrystals exposed to atomic hydrogen

Si nanocrystals embedded in silicon dioxide films are exposed to an atomic hydrogen plasma at different temperatures in the range from 100 °C to 350 °C. The photoluminescence (PL) from the nanocrystals is shown to increase in intensity with increasing exposure time before saturating at a level that depends on the exposure temperature. The saturation level depends on the final exposure temperature and shows no dependence on the thermal history of exposure. This behavior is shown to be consistent with a model in which the steady-state passivation level is determined by a balance between defect passivation and depassivation by hydrogen. Modelling suggests that the difference in activation energies for the passivation and depassivation reactions is ∼0.2 eV, with the activation energy for the passivation reaction being larger than that for the depassivation reaction.