Modified Thornton model for magnetron sputtered zinc oxide: film structure and etching behaviour

ZnO:Al films were prepared on glass substrates with different sputter techniques from ceramic ZnO:Al2O3 target as well as metallic Zn:Al targets using a wide range of deposition parameters. Independent of the sputter technique, sputter pressure and substrate temperature were found to have a major influence on the electrical and structural properties of the ZnO:Al films. With an increasing deposition pressure, we observed a strong decrease in the carrier mobility and also an increase of the etching rate. The surface morphology obtained after etching of RF sputtered ZnO:Al systematically changes from crater-like to hill-like surface appearance with increasing pressure. The correlation of sputter parameters, film growth and structural properties is discussed in terms of a modified Thornton model.