For this study, we evaluated photoinduced surface roughness variation of polycrystalline anatase thin films under different atmospheres using atomic force microscopy (AFM). A TiO2 thin film with large grains was prepared using the sol-gel process and vacuum ultraviolet (VUV) irradiation before firing. Upon UV illumination, the surface image became blurred with an apparent surface roughness increase in ambient air. The appearance of this image change was delayed in dry air, and was not observed in dry nitrogen. These results imply that this photoinduced surface change is related to water adsorption from the atmosphere. (c) 2007 Elsevier B.V. All rights reserved.