Origin of violet photoluminescence in SiO2 films co-doped with silicon and carbon

The Si- and C-codoped SiO2 films were prepared by dual ion beam sputtering technique on p-Si substrates from a SiO2/Si+C composite target. Two photoluminescence (PL) bands at View the MathML source (violet band) and View the MathML source (blue band) can be observed from the as-deposited and annealed samples. The variation tendency of the PL intensity for the two bands versus annealing temperature is different from each other, which may suggest that the two bands have different origins. The X-ray photoelectron spectroscopy, fourier transform infrared spectra, and X-ray diffraction were used to characterize the microstructures. It is suggested that the 470-nm PL band originates from the neutral oxygen vacancy defect. Two possibilities are discussed for explaining the origin of 410-nm PL band from Si- and C-codoped SiO2 films: carbon clusters, and the defects in a region which C clusters are surrounded by the Si–C transitional phase.