Molecular layer-by-layer growth of SrTiO3 and BaTiO3 films by laser molecular beam epitaxy

Layer-by-layer growth of SrTiO3 and BaTiO3 films was achieved by laser molecular beam epitaxy (laser MBE) using SrTiO3 (100) substrate with alomieally Hat terraces and 0.4 nm steps. Fine streak pattern and intensity oscillation were persistently observed by reflection high-energy electron diffraction (RHHED) during the film growth under optimized conditions. When the growth was halted at any levels of RHEED intensity, there was no substantial change in the intensity, which means the growth in a two-dimensional (2-D) layer-by-layer mode without step flow. From the atomic force microscopy (AFM) analysis, it was found that the RHEED oscillation period agreed with the growth time of a molecular layer [MO TiO2 (M = Sr or Ba)] and the oscillation resulted from the periodic change of surface roughness by 2-D epitaxial growth on the terrace.