The present study reports on the growth of thin TiO2 films onto Au(100) single crystals by Ti evaporation in a reactive O-2 atmosphere at two different substrate temperatures: room temperature (RI) and 300 degrees C. The growth of the oxide films was monitored by means of X-ray photoemission spectroscopy, while the valence and conduction band electronic structure was investigated by UV and inverse photoemission spectroscopy, respectively. The TiO2 film grows epitaxially on the Au(100) substrate at 300 degrees C exhibiting the rutile (100) surface. The evolution of the Ti 2p lineshape with the oxide coverage shows the presence of reduced oxide species (characterized by Ti3+ ions) at the Au(100) interface. A crystalline and stoichiometric TiO2 oxide is produced at high substrate temperature, while growth at RI gives a measurable concentration of defects. Post growth annealing in ultra-high vacuum of the RT grown film increases this concentration, while subsequent annealing in O-2 atmosphere restores the sample to the as-grown conditions. (c) 2012 Elsevier B.V. All rights reserved.