Growth, structure, and thermal stability of epitaxial BaTiO3 films on Pt(111)

The growth of epitaxial ultrathin BaTiO3 films upon rf magnetron sputter deposition on a Pt(111) substrate has been studied by scanning tunnelling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy. The BaTiO3 films have been characterized from the initial stages of growth up to a film thickness of 4 unit cells. The deposited films develop a long-range order upon annealing at 1050 K in UHV. In the submonolayer regime a wetting layer is formed on Pt(111). Thicker films reveal a Stranski-Krastanov-like structure as observed with STM. By XPS a good agreement of the thin film stoichiometry with BaTiO3 single crystal data is determined. Due to annealing at 1150 K BaTiO3 forms large two-dimensional islands on the Pt(111) substrate. Different surface structures develop on the islands depending on the O2 partial pressure during annealing.