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Comparison of the ZnO:Al films deposited in static and dynamic modes by reactive mid-frequency magnetron sputtering

: Hong, R.J.; Jiang, X.; Szyszka, B.; Sittinger, V.; Xu, S.H.; Werner, W.; Heide, G.


Journal of Crystal Growth 253 (2003), Nr.1-4, S.117-128
ISSN: 0022-0248
Fraunhofer IST ()
physical vapor deposition process; oxide; zinc compounds

Al-doped zinc oxide (ZnO:Al or AZO) films were deposited on glass substrates by sputtering Zn-Al metallic targets (Al 2 wt%) with an in-line reactive MF magnetron sputtering in both static and dynamic deposition modes. The lateral distribution of the crystalline structure, composition, electrical and optical properties of the films prepared in a static mode were investigated. The films obtained at a central region show cone-shaped grain surface and columnar structure with a lateral grain size of 40-80 nm. In contrast, the film structure obtained at a side region is porous with a grain size of around 30-50 nm. As a result of this lateral structure variation, the carrier concentrations of the film decreased from the target centre to the edge and, inversely, the sheet resistance increased. No significant effect of the erosion craters of the targets on the structure and properties of the film are observed. The lateral inhomogeneity of the properties can be improved by increasing the working gas pressure. The structural, electrical and optical properties for the film deposited in a dynamic mode were comparable with those of the films obtained at central region in the static mode. The conduction mechanism of carrier transport in AZO films is discussed.