Structural, electrical, and optical properties of transparent conductive oxide ZnO:Al films prepared by dc magnetron reactive sputtering

ZnO:Al(ZaO) films were deposited on quartz substrates by de magnetron reactive sputtering from a Zn target mixed with Al. The effect of oxygen flow rate, target to substrate distance, substrate temperature, and Al doping content on the structural, electrical and optical properties of ZAO were investigated. It was observed that the (002) peak position of all films shifts to lower angle comparable to that of bulk ZnO due to the residual stress change with deposition parameters. X-ray photoemission spectroscopy was introduced to analyze the chemical state of Al on the film surface and the results show Al enrichment. The dependences of electrical properties such as resistivity, carrier concentration and Wall mobility on substrate temperature, and Al doping content were measured. The visible transmittance of above 80% and infrared reflectance of above 80% were obtained. The minimum resistivity is 4.23 X 10(-4) Omega cm with the carrier concentration of 9.21 X 10(20) cm(-3) and Hall mobility of 16.0 cm(2) v(1) s(-1). The optical band gap was observed to increase with increasing carrier concentration. The probable mechanisms are discussed. (C) 2001 American Vacuum Society.