Effects of post-hydrogen plasma annealing (HPA) on a-Si:H/SiO2 and nc-Si/SiO, multilayers have been investigated and compared. It is found that photoluminescence (PL) from hydrogen-passivated samples was improved due to the reduction of non-radiative recombination defects. Some interesting difference is that during HPA, atomic hydrogen can directly passivate defects of a-Si:H/SiO2, which results in the reappearance of luminescence band at 760 nm. while for nc-Si/SiO2, hydrogen passivation requires additional thermal annealing after nc-Si/SiO multilayer was treated by HPA. It is indicated that higher atomic mobility is needed to passivate defects at nc-Si/SiO2 interface compared with a-Si:H/SiO2 interface. (c) 2007 Elsevier B.V. All rights reserved.