Time-Voltage Dependent Evolution of Anti-Frenkel Defects in ErMnO₃

The electronic properties of complex oxides can be tuned via oxygen defects, offering intriguing opportunities for precise control of the material’s conductivity. Recently, anti-Frenkel defects moved into focus for minimally invasive property engineering.¹ Anti-Frenkel defects are charge-neutral interstitial-vacancy pairs, and it has been demonstrated that their creation makes it possible to adjust the electronic properties in oxides without causing long-range ionic migration or changes in the overall stoichiometry.<br/>Here, we present a detailed analysis of the electric-field-driven formation and time-voltage dependent evolution of anti-Frenkel defects in hexagonal ErMnO₃. The defects are generated via an electrically biased nano-sized probe tip and imaged by conductive atomic force microscopy and scanning electron microscopy. These spatially resolved measurements allow us to systematically investigate the voltage-driven response of the written defects, complemented by numerical simulations that reproduce the ionic migration. The study reveals that interstitials and vacancies can be split when exposed to an electric field, leading to spatially separated and well-defined vacancy- and interstitial-rich regions, respectively. The results provide new insight into the local electronic properties of ErMnO₃ at the nanoscale and defect physics of functional oxides in general.<br/>¹ D. M. Evans, T. S. Holstad, A. B. Mosberg, D. R. Småbråten, P. E. Vullum, A. L. Dadlani, K. Shapovalov, Z. Yan, E. Bourret, D. Gao, J. Akola J. Torgerson, A. T. J. van Helvoort, S. M. Selbach, and D. Meier, <i>Nat. Mater.</i> 19, 1195 (2020).