Charging ain't all bad: Complex physics in DyScO3

Highlights: • Charging is more than a bane, it can reveal new physics such as flexoelectric bending. • Shift-corrected EELS of DyScO₃ shows evidence of a 3.8 eV surface acceptor state consistent with DFT calculations, and perhaps empty states associated with positive charging. • Negatively charged UPS samples show evidence for Zener-tunneling limited charging. -- Abstract: Although charging is ubiquitous in electron microscopy, its effects are typically avoided or ignored. However, avoiding charging is not possible in some materials, e.g. lanthanide scandates with well-ordered surfaces positively charge immensely under electron beam illumination because of their electronic structure, and ignoring charging can leave new science undiscovered. In this work, a combination of rapidly acquired electron energy loss spectra and cross-correlation were used to understand and overcome charging effects in DyScO₃. A 5.4 eV band gap was extracted from the charging-corrected loss spectrum, in good agreement with previously reported band gaps, and a 3.8 eV in-gap peak was attributed to surface states via comparison with density functional theory calculations. Additionally, ultraviolet photoelectron spectroscopy measurements indicated that under some conditions well-annealed DyScO₃ surfaces charge negatively causing upward band bending associated with occupied surface states in the gap. As was previously found in the case of positive charging under electron beam illumination with in-situ flexoelectric bending observations, the magnitude of negative charging under ultraviolet illumination is Zener tunneling limited in well-annealed DyScO₃.