The crystallinity of zirconia thin films varied with ultraviolet irradiation conditions during thin film preparation. The crystallite size of ZrO2 thin film was the largest in the case of UV irradiation using a low-pressure mercury lamp under 100% O-2 gas at room temperature. The crystallinity of the thin films has depended on their residual carbon contents in the films. The electrical properties of the ZrO2 thin films were greatly improved in the case of UV irradiation using a low-pressure mercury lamp under 100% O-2 gas at room temperature. (c) 2006 Elsevier B.V. All rights reserved.