The mechanisms of blue emission from ZnO films deposited on glass substrate by r.f. magnetron sputtering

ZnO thin films have been deposited on Corning 7059 glass at room temperature using r.f. magnetron sputtering. Strong monochromatic blue emission located at 446 mm is observed when excited with 270 nm light. The photoluminescence intensity of the blue emission peak decreases with increasing oxygen pressure and substrate temperature during film deposition and it increases markedly by annealing in vacuum. The experiments proved that the 446 nm emission corresponds to the electron transition from the shallow donor level of oxygen vacancy and zinc interstitials to the valence band.