Topmost surface and growth mechanism of BaTiO3 thin film grown by laser molecular beam epitaxy

The BaTiO3 thin film was grown epitaxially on SrTiO3(001) substrate by laser molecular beam epitaxy (laser-MBE). The film growth process was monitored by in situ reflection high-energy electron diffraction (RHEED), the regular RHEED intensity oscillation from the 0th-Bragg reflection shows an unit cell layer-by-layer growth mode. The crystalline structure and the surface morphology of the laser-MBE BaTiO3 film were characterized by X-ray diffraction (XRD) and by atomic force microscopy (AFM), respectively. The XRD and AFM results show that laser-MBE BaTiO3 film exhibit the tetragonal c-axis oriented structure and an atomically smooth surface with a root mean square surface roughness of 0.16 nm. The topmost surface of the film was studied by angle-resolved X-ray photoelectron spectroscopy (ARXPS), indicating the laser-MBE BaTiO3 film is predominantly terminated with TiO2 atomic plane. The topmost surface of laser-ablated BaTiO3 film was also analyzed. The film growth mechanism was investigated in atomic scale.