Luminescent characteristics of Si nanocrystallites have been reported depending on deposition condition. Si nanocrystalline thin films on p-type (100) silicon substrate have been prepared by pulsed laser deposition technique using a Nd:YAG laser. Strong blue photoluminescence has been observed at room temperature. The optical properties of thin films have been investigated as functions of laser energy densities, annealing gases, and target-substrate distances. These results indicate that the blue photoluminescence of Si nanocrystallites is related to the quantum size effect of Si nanocrystallites. (c) 2005 American Vacuum Society.