X-ray photoelectron diffraction study of an anatase thin film: TiO2(001)

An anatase thin film, TiO2(001), has been grown by metal–organic chemical vapor deposition on a SrTiO3(001) substrate. The electronic and structural properties of the anatase thin film were investigated by X-ray photoelectron spectroscopy, low energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD). Comparisons of the core-level binding energies for O 1s and Ti 2p3/2 photoelectrons was made between anatase and rutile, and were found to be identical for both polymorphs. Structurally, the surface gave a (1×1) LEED pattern with a high background, indicating regions of good long-range order. Comparison between experimental XPD data and single-scattering cluster calculations indicate that there is good agreement with an anatase crystal termination, and poor agreement with a rutile crystal termination. Furthermore, good agreement was found at low takeoff angles for experiment and calculations suggesting that the thin film has good short-range order at the surface. This study indicates that anatase is stable and does not undergo a transformation to the rutile polymorph when exposed to atmosphere after film growth or after heating to low temperatures in ultrahigh vacuum.