White-light emission from annealed ZnO:Si nanocomposite thin films

As grown ZnO:Si nanocomposites of different compositional ratios were fabricated by thermal evaporation techniques. These films were subjected to post-deposition annealing under high vacuum at a temperature of 250 °C for 90 min. The photoluminescence (PL) spectra of annealed samples have shown marked improvements both in terms of intensity and broadening. Structural and Raman analyses show formation of a Zn–Si–O shell around ZnO nanoclusters wherein on heating Zn2SiO4 compound forms resulting in huge UV, orange and red peaks at 310, 570 and 640 nm in PL. The new emissions due to Zn2SiO4 completes white light spectrum. The study not only suggests that 1:2 ratio is the best suited for material manipulation but also shows process at the interface of ZnO nanoclusters and silicon matrix leads to new PL emissions.