Blue luminescent center in ZnO films deposited on silicon substrates

Polycrystalline ZnO films have been deposited on Si substrates by RF actively sputtering technique. The photoluminescence (PL) spectra of the ZnO films show the blue emission peaks centered at 430 nm. The variation of these peak intensities and that of the free-carrier concentration were investigated at different annealing temperatures. The defect levels in ZnO films were also calculated using the method of full-potential linear muffin-tin orbital. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band.