Paper TF1-FrM7
Other Impurity-co-doping Effect on the Stability of Resistivity in AZO and GZO Transparent Conducting Thin Films

Friday, October 19, 2007, 10:00 am, Room 602/603

It has been recently reported that the resistivity of Al-doped ZnO (AZO) and Ga-doped ZnO (GZO) transparent conducting thin films with a thickness below approximately 100 nm always increased when tested in heated high humidity environments. For the purpose of improving the resistivity stability in these films for use in heated moist environments, the effect of impurity-co-doping on the stability of resistivity was investigated for AZO and GZO transparent conducting thin films. The impurity (X)-co-doped AZO and GZO (AZO:X and GZO:X) transparent conducting thin films were prepared on glass substrates by dc (both with and without incorporated rf) magnetron sputtering, rf magnetron sputtering and pulsed laser deposition methods. AZO and GZO thin films co-doped with V or In were prepared with thicknesses in the range from approximately 20 to 200 nm at a temperature of 100-200^oC. The resulting thin films were investigated using micro-structural analyses such as EXAFS and TEM. The stability tests were conducted long term (up to 1000 h) in a high humidity environment (air at 90% relative humidity and 60^oC). It was found that the resistivity stability of AZO:V thin films was considerably improved by optimizing the content of co-doping V. In particular, AZO:V films with a thickness of 50 nm were stable enough to be acceptable for use in practical transparent electrode applications. In contrast, thin films with a thickness below approximately 30 nm were always unstable under the above test condition. The resistivity increase of films with a thickness below 30 nm is mainly attributable to carrier transport being dominated by the trapping of free electrons due to oxygen adsorption on the film surface rather than the grain boundary.