Epitaxial BaTiO3(100) films on Pt(100): A low-energy electron diffraction, scanning tunneling microscopy, and x-ray photoelectron spectroscopy study

The growth of epitaxial ultrathin BaTiO3 films on a Pt(100) substrate has been studied by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and x-ray photoelectron spectroscopy (XPS). The films have been prepared by radio-frequency-assisted magnetron sputter deposition at room temperature and develop a long-range order upon annealing at 900 K in O-2. By adjusting the Ar and O-2 partial pressures of the sputter gas, the stoichiometry was tuned to match that of a BaTiO3(100) single crystal as determined by XPS. STM reveals the growth of continuous BaTiO3 films with unit cell high islands on top. With LEED already for monolayer thicknesses, the formation of a BaTiO3(100)-(1 x 1) structure has been observed. Films of 2-3 unit cell thickness show a brilliant (1 x 1) LEED pattern for which an extended set of LEED I-V data has been acquired. At temperatures above 1050 K the BaTiO3 thin film starts to decay by formation of vacancy islands. In addition (4 x 4) and (3 x 3) surface reconstructions develop upon prolonged heating. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633703]