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 $250{\mathrm{C}}^{\mathrm{o}}$ for 90min. The photoluminescence (PL) spectra of annealed samples have shown marked improvements both in terms of intensity and broadening. For the first time in ZnO:Si nanocomposite films we see huge UV, red and orange peaks at 310, 570 and 640nm. Structural and Raman analysis show formation of a Zn-Si-O shell around ZnO nano clusters wherein on heating $\mathrm{Z}{\mathrm{n}}_2\mathrm{S}\mathrm{i}{\mathrm{O}}_4$ compound forms. The new emissions are due to $\mathrm{Z}{\mathrm{n}}_2\mathrm{S}\mathrm{i}{\mathrm{O}}_4$ which completes white light spectrum.