Si thin films on p-type (1 0 0) Si substrates have been prepared by using pulsed laser deposition (PLD). The optical and structural properties of these films have been investigated as functions of the deposition temperatures and annealing temperatures. Films were deposited from p-type silicon target in He ambient gas pressure of 1 Torr at different deposition temperatures ranging from room temperature to 400 degreesC. After deposition, the silicon thin films were annealed in nitrogen gas at different annealing temperatures ranging from 400 to 800 degreesC. When the deposition temperature increases, photoluminescence (PL) intensity abruptly decreases and PL peak shows red shift. As annealing temperature increases, intensity of blue (430 nm) peak increases. On the contrary, that of green (580 nm) peak decreases because of decrease of defect centers. Possible mechanisms of nanostructure formation and PL origin are discussed. (C) 2003 Published by Elsevier B.V.