Domain wall currents and ferroelectric domain structures of PbTiO₃ thin films on highly oriented pyrolytic graphite (HOPG) substrates

We investigated the growth and ferroelectric properties of PbTiO₃ (PTO) thin films deposited on a highly oriented pyrolytic graphite substrate with an atomic structure similar to a graphene surface. Polycrystalline PTO thin films with good crystallinity were formed using a pulsed laser deposition method, as confirmed by X-ray experiments. The polycrystalline PTO thin films exhibited excellent ferroelectric properties, with a high remanent polarization of 38.5 μC/cm² and a remanent piezoelectric constant of approximately 40 pm/V. Piezoresponse force microscopy revealed the mosaic domain structure of the PTO thin films, which had a slightly lower domain wall energy compared to epitaxial PTO thin films. Moreover, atomic force microscopy allowed the observation of the current domain structure corresponding to the ferroelectric domain structure, with higher currents formed in the domain walls and decreased upon the removal of the domain walls.