266 nm pulsed laser-induced oxygen atoms desorbed from 873 K high temperature, high vacuum pretreated rutile TiO2

Desorption of neutral oxygen atoms induced by 266 nm laser pulses from pressure pressed as-prepared (AP) sample and from high temperature (873 K, 40 h) pretreated (HT) sample is investigated by time-of-flight (TOF) mass spectrometric analysis. The obtained TOF data are analyzed by Maxwell-Boltzmann energy distributions. It is concluded that desorption of neutral oxygen atoms occurs from oxygen defect sites via photochemical processes, followed by some subsequent thermal quenching processes. Kinetic energies of desorbed species are reflected by the sub-band structure in the band gap of TiO2. Band gap energies of the AP sample and the HT sample are estimated to be 2.02 and 2.37 eV, respectively, in accordance with values obtained from previous theoretical calculations. The surface of the HT sample was studied with ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) to elucidate laser irradiation effects. (C) 2000 Elsevier Science B.V. All rights reserved.