UV irradiation of sol-gel derived HfO2 thin films in N2O using excimer lamps was found to effectively remove OH groups, dissociate unreacted Hf-OH and further oxidize sol-gel layers, forming HfO2 thin films with a high stoichiometry of 1.97. No interface oxidation and silicate formation has been observed when irradiated at 400 degreesC for 20 min while the films retain a desired amorphous structure. UV-irradiated sol-gel layers exhibited significantly improved optical properties, with high optical transmittances of 81-97% in the visible region of the spectrum, a high refractive index of up to 1.90 being achieved. A leakage current density as low as 5.8 x 10(-6) A cm(-2) at 1 MV cm(-2) and breakdown field of larger than 5 cm(-2) were obtained on these sol-gel layers with radiation for 20 min. (C) 2002 Elsevier Science B.V. All rights reserved.