Transmission electron microscopy study of n=1-5 Srn+1TinO3n+1 epitaxial thin films

Epitaxial Srn+1TinO3n+1 thin films with n = 1-5 were synthesized on (001) S rTiO3 substrates by reactive molecular beam epitaxy. The structure and micr ostructure of the films were investigated by x-ray diffraction, transmissio n electron microbeam diffraction, and high-resolution transmission electron microscopy (HRTEM) in combination with computer image simulations. Both di ffraction and HRTEM studies revealed that all the films are epitaxially ori ented with their c axis perpendicular to the (001) SrTiO3 plane of the subs trate. Detailed investigations using quantitative HRTEM methods indicated t hat the films have the expected n = 1-5 structures of the Ruddlesden-Popper Srn+1TinO3n+1 homologous series. Among these films, Sr2TiO4, Sr3Ti2O7, and Sr4Ti3O10, thin films are nearly free of intergrowths, while Sr5Ti4O13 and Sr6Ti5O16 thin films contain noticeably more antiphase boundaries in their perovskite sheets and intergrowth defects. We show that these results are consistent with what is known about the thermodynamics of Srn+1TinO3n+1 pha ses.