A spin-coated sol-gel method for the fabrication of highly porous or smooth ultra-thin ZrO2 films was developed. By spin-coating sol solutions, which contained ZrCl4 in anhydrous isopropanol, on substrates, the morphology and thickness of thin films were easily controlled by changing the concentrations of ZrCl4 in sol solutions. A highly porous film with large specific surface area (180 m(2)/g) was obtained at 150 g ZrCl4/l without the addition of templates. When the concentration of ZrCl4 decreased to 17 g/l, the porous surface turned into a smooth thin film. A linear relationship between film thicknesses and concentrations of ZrCl4 ranging from 17 to 3 g ZrCl4/l was observed, and an ultrathin film with the thickness of 1.8 nm was achieved when 3 g ZrC14/1 was used. Results obtained in this study clearly show that spin coating of anhydrous sol solution is an efficient method for the fabrication of Zr02 films with controllable morphology and thickness. (c) 2005 Elsevier B.V All rights reserved.