Direct, spatially resolved observation of defect states with electromigration and degradation of single crystal SrTiO₃

Laterally and depth-resolved cathodoluminescence spectroscopy (DRCLS) provided direct, nanoscale measurements of oxygen vacancy and oxygen vacancy complex distributions in undoped and Fe-doped SrTiO₃ with high temperature electric field stress associated with dielectric resistance degradation. DRCLS provided direct and spatially resolved observation of oxygen vacancy migration driven by external electric fields from the anode to the cathode in undoped SrTiO₃ between laterally separated electrodes, resulting in increased current leakage and lower thermal breakdown strength. DRCLS measurements through planar Pt electrodes after high temperature electric field cycling reveal pronounced oxygen vacancy depletion within the surface space region of the Pt/SrTiO₃ Schottky barrier as predicted theoretically. These results provide a direct insight into the transient states impacting the conduction during the electromigration of the oxygen vacancies. The deconvolution of different peaks and their intensity variations relative to the direct bandgap provide methods to gauge the relative defect energetics of these gap states. These data are discussed in relation to providing a tool to further understand conduction in mixed ionic conductors.