Silicon quantum dots have been grown in situ in amorphous silicon nitride (SiNx) films on silicon substrate by plasma-enhanced chemical vapor deposition using ammonia (NH3) and silane (SiH4) as reactant gases. After deposition, films were annealed in N-2 atmosphere at temperatures ranging from 700 to 1000 degrees C for 1 min using rapid thermal annealing system. The evolution of the Si quantum dots (QDs) and the chemical composition of the films have been investigated by Raman scattering and infrared absorption spectroscopy, and the correlation with the optical properties is presented. From the photoluminescence measurements, the position and the intensity of the photoluminescence peak were studied as a function of the annealing temperature (T-a), and the luminescence mechanism in Si QDs-SiNx composite structures is attributed to the quantum confinement in silicon clusters. These results lead to further understanding the physical and optical properties of Si QDs embedded in silicon nitride films and thus open up the possibility of realizing efficient Si-based tandem solar cells. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3225601]