Structural Characterization of Zinc-Tin-Oxide Films Deposited on Quartz Substrates by Radio Frequency Magnetron Sputtering

Abstract

ZnO-SnO2 (ZTO) thin films were grown by radio frequency sputtering on quartz substrates at various substrate temperatures, T-S. X-ray diffraction (XRD) data showed that the ZTO films underwent an amorphous-to-crystalline phase transition with increasing T-S. Also Zn K-edge X-ray absorption near edge structure showed that the ZTO films deposited at T-S <= 450 degrees C started to crystallize. This trend was confirmed by XRD and extended X-ray absorption fine structure analysis. AFM studies of the ZTO films indicate that the surfaces are fairly smooth with root-mean-squared surface roughness of 1.04 to 3.55 nm. The average transmittance of the ZTO films in the visible region was >= 85%, and the band gap blue-shifted as T-S increased. The lowest resistivity was on the order of 10(-2) Omega . cm for films deposited at T-S >= 650 degrees C: films deposited at T-S <= 450 degrees C were weakly conducting. The conductivity of films increased as T-S increased. These results can guide modifications of ZTO for applications that incorporate electrically-conducting, optically-transparent thin films.