Epitaxial BaTiO3 thin films grown in unit-cell layer-by-layer mode by laser molecular beam epitaxy

Two-dimensional (2-D) layer-by-layer epitaxial growth of BaTiO3 (001) film on the atomically flat SrTiO3 (100) substrate was investigated in an atomic scale by in situ analyses of reflection high energy electron diffraction ( RHEED) and coaxial impact collision ion scattering spectroscopy (CAICISS) a s well as ex situ atomic force microscopy (AFM). Under the optimized growth condition in laser molecular beam epitaxy (laser MBE), we could observe th e intensity oscillations at the specular beam spot in RHEED pattern during the deposition. One period of the intensity oscillations corresponded to th e growth of a 0.4 nm thick film, which indicates that the growth unit layer in the 2-D growth mode is one molecular layer of [BaO/TiO2]. Through the A FM observation of the surface morphology of the films, the growth of which was halted at a RHEED intensity maximum or minimum, we clarified that the R HEED intensity oscillations was caused by the 2-D nucleation and growth of one molecular layer. From in situ CAICISS measurements, it was found that t he terminating plane of BaTiO3 (001) films (80 nm thick) grown by the prese nt conditions was the BaO atomic plane. (C) 1998 Elsevier Science S.A. AU r ights reserved.