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 >10Amm^-2. The breakdown field was as high as 0.45MVcm^-1 at the forward bias, while no breakdown occurred up to 0.5MVcm^-1 at the reverse bias.