(Ba,Sr)TiO₃ solid solution thin-films grown by a molecular beam epitaxy method

(Ba,Sr)TiO₃ thin films were prepared on SrTiO₃ (001) substrates by a molecular beam epitaxy technique. (Ba,Sr)O and TiO₂ monolayers were alternately grown in twenty cycles to produce films of 8 nm thick. The growth mechanism of the films was elucidated from reflection high energy electron diffraction and atomic force microscopy. An island growth mechanism was found to be predominant, and activation energies for the surface migration of Sr/Ba and Ti were determined to be 0.31 and 0.33 eV, respectively. According to coaxial impact collision ion scattering spectroscopy measurements, the atomic configuration of the film surface improved when the ratio Sr/Ba increased from Ba_0.514Sr_0.486TiO_3.56 to Ba_0.304Sr_0.696TiO_3.50.