Titanium oxide thin films on glass and silicon wafer substrates were prepared by the sol-gel process. The pH variation and the calcination effect on the optical and structural properties of the films were systematically examined. The coated films were characterized by atomic-force microscopy (AFM), NKD analyzer, X-ray diffraction (XRD) and cyclic voltammograms (CV). The influence of calcination and pH value on the spectra of transmittance, reflectance, and refractive indices and on the surface structure has been investigated. From X-ray diffractometric measurements (XRD), it has been confirmed that the films are an anatase form. The effects of pH and surface modification of titanium oxide were studied with AFM images. These showed that the surface texture was changed dramatically according to calcinations and pH variation. Spectral dependencies of refractive indices (n) were determined for all films. Band-gap energy (E-g) was also estimated for these films. (C) 2005 Springer Science + Business Media, Inc.