Preparation and characterization of ZnO:Al films by pulsed laser deposition

High transmittance, low resistivity, and c-axis highly oriented ZnO:Al thin films on glass substrate were obtained by laser ablation at different deposition conditions. These films were deposited with an excimer (KrF) laser beam of lambda = 248 nm operated under the conditions of 7.0 J cm(-2) energy density and 5 Hz repetition rate. The electrical and optical properties were found to depend on substrate temperature and doping ratio of Al. From electrical and optical analyses we observed that the carrier concentration, optical transmittance and optical energy gap the ZnO:Al transparent conductive oxides increased when the deposition temperature is raised from 200 degrees C to 300 degrees C. X-ray diffraction analyses showed that the crystallinity of the film became better with increasing temperature, and indicated that the crystallinity of the film determined its electrical and optical properties. The film prepared at 300 degrees C using a target of doping ratio of 1.5% Al2O3 is strongly c-axis-oriented polycrystalline, and has a low resistivity of 9.0 X 10(-4) Ohm cm, a carrier concentration of 5.8 x 10(20) cm(-3) and a transmittance of about 90% in the visible range. However, the crystallinity of the film prepared at 500 degrees C became poor, and its resistivity also became higher. (C) 1997 Elsevier Science S.A.