Growth of stoichiometric TiO2 thin films on Au(100) substrates by molecular beam epitaxy

Abstract

The present study reports on the growth of thin TiO2 films onto Au(100) single crystals by Ti evaporation in a reactive O2 atmosphere at two different substrate temperatures: room temperature (RT) and 300°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°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 RT 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 O2 atmosphere restores the sample to the as-grown conditions.