Influence of oxygen partial pressure on structural, electrical, and optical properties of Al-doped ZnO film prepared by the ion beam co-sputtering method

Aluminum doped zinc oxide (AZO) films were prepared at room temperature by ion beam co-sputtering system under various oxygen partial pressures. The structural, electrical, and optical properties of the films were studied by XRD, XPS, Hall measurement, and spectrometer. The AZO film with low resistivity, 7.8 x 10(-4) Omega cm, and high transparency, similar to 80 %, was obtained at the optimum oxygen partial pressure of 1.3 x 10(-4) Torr and the intense (002) diffraction peak was observed simultaneously. Different optical band gaps observed in the films prepared under various oxygen partial pressures are closely related to the carrier concentrations in the films. Three O-1s components were applied to fit the XPS O-1s spectra. They consist of adsorbed oxygen species, oxygen in O-Zn bonds surrounded by oxygen vacancies, and oxygen in the O-Zn bonds. Two components, Zn in Zn-O bonds and Zn with higher than +2 oxidation states, were used to fit Zn-2p3/2 spectra. It was found that the increase of film's resistivity which may result from the drops in the oxygen vacancy, Zn interstitial, carrier concentration, and grain size. No apparent transmission change of the film in the visible light region as a function of oxygen partial pressure was detected.