Structural and photoluminescence properties of Al-doped ZnO films deposited on Si substrate

Al-doped ZnO (ZnO:Al) thin films were deposited on Si substrates using the radio-frequency reactive magnetron sputtering technique. Effect of Al contents and annealing treatments on the structural and photoluminescence (PL) properties of ZnO films was investigated. The results showed that crystallinity of the films improved first with the increasing of Al content. However, as the Al content further increased more than 0.75 wt %, the crystallinity was deteriorated. Meanwhile, the crystal quality of ZnO:Al thin films (Al content is 0.75 wt %) was markedly improved after annealing at 600 °C for 0.5 h. Four main emission peaks located at 390, 445, 490 and 530 nm were observed from PL spectra. As Al content was increased to 1.14 wt %, the intensity of the blue peak (∼445 nm) and the green peak (∼490 nm) increased and the full width at half maxima (FWHM) decreased, and blue centre blue shifted to 429 nm. A similar result can be obtained after annealing 600 °C for 0.5 h. This is attributed to Al doping and annealing treatment lead to the change of contents of antisite oxygen and interstitial Zn-related defects in the films.