Anomalous effect due to oxygen vacancy accumulation below the electrode in bipolar resistance switching Pt/Nb:SrTiO₃ cells

In conventional semiconductor theory, greater doping decreases the electronic resistance of a semiconductor. For the bipolar resistance switching (BRS) phenomena in oxides, the same doping principle has been used commonly to explain the relationship between the density variation of oxygen vacancies (Vö) and the electronic resistance. We find that the Vö density can change at a depth of ~10 nm below the Pt electrodes in Pt/Nb:SrTiO₃ cells, depending on the resistance state. Using electron energy loss spectroscopy and secondary ion mass spectrometry, we found that greater Vö density underneath the electrode resulted in higher resistance, contrary to the conventional doping principle of semiconductors. To explain this seemingly anomalous experimental behavior, we provide quantitative explanations on the anomalous BRS behavior by simulating the mobile Vö [J. S. Lee et al., Appl. Phys. Lett. 102, 253503 (2013)] near the Schottky barrier interface.