Ferroelectric properties and piezoresponse force micoroscopy study of BiTaTiO thin films.

We investigate the ferroelectric properties and crystal structures of BiTaTiO (BTTO) thin films deposited on single-crystal Nb-doped (100) SrTiO substrates via pulsed laser deposition. The BTTO films exhibited either a (001)-epitaxial crystalline structure or a mixed a- and c-oriented polycrystalline structure depending on the substrate temperature. The ferroelectric polarization and piezoelectric coefficient of the mixed a- and c-oriented film were larger than those of the (001)-epitaxial film because its polar axis was perpendicular to the c-axis. Vertical and lateral piezoresponse force microscopy studies indicate that the ferroelectric domains of the (001)-epitaxial film were all parallel to the in-plane orientation, whereas the mixed a- and c-oriented film comprised both square grains with in-plane-oriented ferroelectric domains and longish grains with ferroelectric domains out of orientation with the plane.