Nanoscale Mapping of Potential Barrier Degradation at BaTiO₃-Ni Interfaces

Scanning Kelvin probe microscopy was used to investigate the evolution of the Ni-BaTiO3 interfacial potential barriers in multilayer ceramic capacitors degraded by the highly accelerated life test method. We detect electric field discontinuities at such interfaces, which through analysis of the expected band diagrams, are associated with the presence of Schottky barriers. The decrease of discontinuities at the cathode in degraded capacitors denotes barrier lowering, indicative of a transition from Schottky to Ohmic contact, validating the proposed mechanism of oxygen vacancies electromigration being at the origin of insulation resistance degradation. Extrapolation of the depletion layer width is consistent with previous observations, and the possibility toward the use of this technique to obtain quantitative information is discussed.