Oxygen‐deficient ordered phases of ultrathin BaTiO 3 films on Pt(111)

The restructuring of epitaxial ultrathin BaTiO 3 films on a Pt(111) substrate upon high‐temperature treatment has been studied by scanning tunneling microscopy, low‐energy electron diffraction, and XPS. Upon annealing ultrathin BaTiO 3 films up to 4 monolayer equivalents in thickness at 1150 K in vacuum, BaTiO 3 forms three‐dimensional islands surrounded by bare Pt. Annealing at 1250 K induces a two‐dimensional rewetting layer, which spreads around the three‐dimensional BaTiO 3 islands. This rewetting layer consists of oxygen‐deficient BaTiO 3 . Within the rewetting layer, several long‐range ordered structures coexist. Their lattice constants vary between 11 and 46 Å. These rewetting structures are derived from a slightly modified BaTiO 3 (100) layer, which is stabilized by one direction of the Pt(111) lattice. The rewetting layer formation can be reversed by annealing in oxygen. Copyright © 2012 John Wiley & Sons, Ltd.