Hetero-epitaxial BaTiO3 layers were formed on the MgO(1 0 0) surface by thermal evaporation of titanium followed first by oxidation at 400 C, subsequently by barium evaporation, and finally by annealing at 800 C. The atomic structure of BaTiO3 layers was investigated by the scattering intensity variation of He+ ions on time-of-flight impact-collision ion scattering spectroscopy and by patterns of reflection high energy electron diffraction. The result of our investigation reveals that cubic perovskite structured BaTiO3 layers with the lattice parameter of bulk phase are grown on the MgO(1 0 0) surface. (C) 2003 Elsevier B.V. All rights reserved.