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 react ive sputtering from a Zn target mixed with Al. The effect of oxygen flow ra te, target to substrate distance, substrate temperature, and Al doping cont ent on the structural, electrical and optical properties of ZAO were invest igated. 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 chan ge with deposition parameters. X-ray photoemission spectroscopy was introdu ced to analyze the chemical state of Al on the film surface and the results show Al enrichment. The dependences of electrical properties such as resis tivity, carrier concentration and Wall mobility on substrate temperature, a nd Al doping content were measured. The visible transmittance of above 80% and infrared reflectance of above 80% were obtained. The minimum resistivit y 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 wa s observed to increase with increasing carrier concentration. The probable mechanisms are discussed. (C) 2001 American Vacuum Society.