Band offsets at heterojunctions between SrTiO3 and BaTiO3 and Si(100)

We use thin (similar to26 Angstrom) SrTiO3 and BaTiO3 films epitaxially grown on Si(100) substrates, and ultraviolet and x-ray photoemission spectroscopy to investigate band discontinuities at the SrTiO3/Si and BaTiO3/Si heterojunctions. The treatment of the oxide film surface ranges from ex situ ultraviolet generated ozone to annealing in O-2 or ultrahigh vacuum. Depending on surface treatment, the valence band offset varies from 2.38 to 2.64 eV for SrTiO3/Si heterostructure and from 2.35 to 2.66 eV for BaTiO3/Si. These values imply that the conduction band minimum of the oxide is below that of the semiconductor, a situation referred to as negative conduction band offset. We demonstrate that the SrTiO3/Si and BaTiO3/Si interfaces undergo significant chemical changes during surface cleaning of the oxide film. (C) 2004 American Institute of Physics.