Effects of Ti buffer layer on the absorption characteristic and fluorescence spectrum of ZnO films

ZnO films using different thick Ti buffer layers were deposited on Si and glass substrates by radio frequency (RF) reactive magnetron sputtering. The effect of buffer layers on the absorption characteristic and fluorescence spectrum of ZnO films was characterized by ultraviolet-visible spectrophotometer and fluorescence spectrophotometer. The results revealed that all films had an average optical transparency over 80% in the visible range, the UV absorption edge shifted to a longer wavelength after Ti buffer introduced and shifted to a shorter wavelength as the thickness of Ti buffer increased. Three main emission peaks including a UV located at about 390 nm, two blue peaks located at about 435 and 487 nm and two green peaks located at about 525 and 560 nm were observed from the PL spectra. The origin of these emissions was discussed.