Thin BaTiO_(3) films grown on SrTiO_(3) substrates were characterized by means of positron annihilation. The films were deposited by molecular-beam epitaxy without using oxygen source. We measured the Doppler broadening spectra of annihilation radiation and x-ray diffraction of the films and found that vacancy-type defects such as oxygen vacancies and other related defects caused lattice relaxation in the films. These defects disappeared after the films were annealed at 600℃ in an O_(2) atmosphere. Lattice relaxation in the films was also observed when the films were annealed at 1050℃, but there was no direct relationship between the lattice relaxation that occurred at this temperature and vacancy-type defects. Vacancy-type defects were introduced into the SrTiO_(3) substrates by the growth of the BaTiO_(3) films. The species of these defects were identified as oxygen vacancies or defects related to oxygen vacancies, and they appeared as a result of diffusion of oxygen toward the BaTiO_(3) films. Almost all oxygen vacancies in the SrTiO_(3) substrates were annealed out at 500℃.
展开▼
