ZnO thin films were deposited on a-plane alumina by electron cyclotron resonance-assisted CVD method at several substrate temperatures. The crystal orientation of ZnO thin film strongly depended on the substrate temperature. The full width at half maximum of (002) rocking curve improved from 7 degrees of ZnO film deposited at 300 degrees C to 0.4 degrees of that deposited at 600 degrees C. The hydrogen impurity in ZnO thin film decreased with increasing the substrate temperature. The behavior of hydrogen impurity is related with the degree of c-axis orientation. (c) 2005 Published by Elsevier B.V.