Influence of annealing under reducing ambient on properties of ZnO thin films prepared by mist CVD

The resistivity of ZnO thin films grown at 300 °C with mist CVD method can be decreased about 3 orders of magnitude, from 6.2 Ωcm as deposited to 2.2×10-2 Ωcm for the film after post annealing at 350 °C under reducing ambient of 5% H2 in N2 (forming gas: FG) with increasing mobility and without changing carrier density. It is thought that the electrical properties of the ZnO thin films with a large amount of impurities due to the low temperature growth are changed without changing surface morphology, crystal structure and impurity content after annealed in the reducing ambient. This can be explained by the decrease of disorder in the band gap in the grain and lowering of the Schottky barrier height in the grain boundaries due to the H2 interaction with oxygen. The model is supported by the quick decrease of resistivity under FG annealing. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)