Optical properties of anatase TiO2 thin films prepared by aqueous sol-gel process at low temperature

TiO2 thin films were spin-coated on Si (100) substrates via an aqueous sol-get route using Ti(OBun)(4) and H2O2 as starting materials, and were annealed in air at different temperatures up to 550 degreesC for I h. X-Ray diffractometry indicates that crystallization into anatase started at 350 degreesC. The 350 degreesC-annealed films were further characterized by Auger electron spectroscopy, X-ray photoelectron spectroscopy, and variable angle spectroscopic ellipsometry. The results show that homogeneous, carbon-free TiO2 films with high refractive index (n=2.3 at 550 nm) were successfully obtained under an annealing temperature as low as 350 degreesC. The indirect and direct optical absorption bandgaps, of the anatase film are estimated as 3.23 and 3.80 eV, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.