Synthesis and characterization of silicon quantum dots (Si QDs) materials are carried out. The Si QDs were prepared from a hydrogenated silicon rich nitride film that is deposited by the plasma enhanced chemical vapor deposition process with a gas mixture of SiH4 and NH3 at flow ratios from 0.5 to 2. The Si QDs can be precipitated from the hydrogenated silicon rich nitride film by a high temperature annealing. The optimum density of the Si QDs precipitated amounts to 6.4x10(12) cm(-2), as calculated from transmission electron microscope images, for flow ratio of SiH4 versus NH3 at 2, and particle sizes less than 6 nm. The dots density within the film becomes concentrated when the flow ratio of SiH4 versus NH3 increases. The intensity of photo response increases drastically when the dots density becomes large. (C) 2012 Elsevier B.V. All rights reserved.