Recurrent local resistance breakdown of epitaxial $BaTiO3$ heterostructures

Leakage current through epitaxial $BaTiO3$ films was investigated to clarify the difference between the characteristics of nanometer and millimeter-size metal contacts. $SrTiO3:Nb$ bottom electrode revealed genuine properties of a single metal/$BaTiO3$ contact and demonstrated that breakdown voltage and leakage current density at both nanometer and millimeter-size contacts were controlled by the Schottky barrier. However, in marked contrast with millimeter-size contacts, nanometer-size contacts conducted little current below breakdown voltage and repeatedly exhibited abrupt breakdowns having a giant current density $>10 A mm−2.$ The breakdown field was as high as $0.45 MV cm−1$ at the forward bias, while no breakdown occurred up to $0.5 MV cm−1$ at the reverse bias.