Investigation of Microstructure and Ferroelectric Domain of Epitaxial PbTiO3 Thin Film Grown by Liquid Phase Deposition

In this research, PbTiO3 (PTO) thin films with 150 nm thickness were grown on (001) Nb-doped SrTiO3 substrate. High-resolution X-ray diffraction (HR-XRD) studies showed that the PTO films are epitaxial with [001] orientation. The ф-scan of the film and substrate around {102} revealed a fourfold symmetry for both demonstrating [001] perfect orientation of the films. XRD reciprocal space map around (103) of the film and substrate revealed that film is fully strained with a compressive strain. The lattice constants calculated from the horizontal and vertical peak positions are; a = 0.403 nm and c = 0.407 nm. This compressive strain was developed due to the coherent interface formation in the film and substrate interface and the lattice parameter mismatch of the film with respect to the substrate. Topography studies by atomic force microscopy (AFM) showed that films are highly uniform with densely packed elongated grains developed along the [100] and [010] orientations. Ferroelectric domain configuration of the film was investigated by a piezoelectric force microscope (PFM). Two types of 180 and 90 degrees ferroelectric domains were observed. The epitaxial compressive strain is responsible for the formation of 90 degree domains. The developed strain via the lattice mismatch between the PTO layer and the substrate enforces electrical dipoles to rotate away from the normal direction to compensate the elastic energy of the film.