Initial growth stages of titanium and barium oxide films on SrTiO3(001)

Ultrathin titanium and barium oxide films were grown on SrTiO3(001) substrate surfaces via Ti/Ba deposition and oxidation. When Ti is deposited onto the SrTiO3(001) surface, it forms a series of SrTiO3 surface reconstructions such as c(4 × 2), 5×5−R26.6∘, (6 × 2) and (9 × 2), which can be controlled by varying the Ti concentration. Epitaxial anatase TiO2(001) islands with (1 × 3) and (1 × 5) reconstructions are formed by further increasing the Ti deposition amount and post-annealing. The initial growth of BaO thin films depends on the surface condition of the substrate. BaO nanoparticles form on reconstructed SrTiO3(001), while a locally ordered c(4 × 4) BaO structure is observed on the disordered sample surface. Co-deposition of Ba and Ti on SrTiO3(001) results in phase separation with the deposited Ba forming BaO nanoparticles and the Ti contributing to Ti-rich SrTiO3 surface reconstructions. No formation of BaTiO3 is observed at the initial growth stages between 0.3 monolayer (ML) and 1.8 MLs.