Ellmer, K.; Welzel, T.: Reactive magnetron sputtering of transparent conductive oxide thin films: Role of energetic particle (Ion) bombardment. Journal of Materials Research 27 (2012), p. 765-779
10.1557/jmr.2011.428
Abstract:
Transparent conductive oxides (TCO) are degenerately doped compound semiconductors with wide band gaps (Eg > 3 eV) that are used as transparent electrodes in optoelectronic devices. Reports on the influence of negative ions on the electrical properties of TCO films are reviewed and compared with our own results. It was reported that the radial resistivity distributions depend (i) on the excitation mode of the magnetron (DC or RF), (ii) on the erosion state of the sputtering target and, (iii) on the density of the ceramic targets. This can be explained by the fact that the negative ions in magnetron discharges (in our case O-) are generated at the target surface and accelerated towards the growing films. Its energy and its radial distribution depend on the discharge voltage and the shape of the emitting surface, i.e., of the erosion groove. Ways for reducing the effect of negative ion bombardment are discussed.