In this study, Si-rich silicon oxide (SiO1.56) films are fabricated by reactive sputtering and subsequently annealed at high temperature in N-2 or Ar atmosphere. High-resolution transmission electron microscopy (HRTEM) and Raman spectrum confirms the formation of silicon nanocrystals (nc-Si). After the first step annealing process, oxygen is introduced as a post-annealing atmosphere. It has been observed that the photoluminescence properties of the films change dramatically due to the post-annealing, and the variation differs depending on the first-step annealing atmosphere. The mechanism of this phenomenon has been discussed and it has been concluded that the post-annealing mainly serves as both a passivation and an oxidation process at the nanocrystal interface. Oxygen is considered to be a more stable passivating atmosphere for SiOx films annealed in N-2 at high temperatures instead of H-2. (c) 2005 Elsevier B.V. All rights reserved.