Directly Visualizing the Formation of Artificial Structures and Their Charge in Oxides by Electron Microscopy

Atomic-scale heterogeneities in perovskite oxides give rise to exotic functionalities, presenting exciting opportunities for next-generation microelectronic devices. However, reliably introducing and stabilizing atomic defects in a controlled manner remains challenging. Here, we demonstrate the precise creation of single potassium (K) vacancies and columnar K4Ta9O27 structures in the paraelectric perovskite KTaO3 at the atomic and unit-cell levels using a subatomic size electron probe in an aberration-corrected scanning transmission electron microscope. We further directly probed the electric field and charge associated with a single K vacancy. High-resolution electric field imaging reveals that these K vacancies generate strong inward-pointing electric fields and carry a negative charge, which could alter their local electrostatic environment and influence material properties. Density functional theory calculations confirm that the K4Ta9O27 phase is conductive and the ionic rearrangement facilitates the formation of coherent structures that seamlessly integrate with the native KTaO3 lattice. This method, not only in precisely creating and stabilizing atomic-scale defects but also in directly probing their fundamental electric properties, provides a robust approach to the deliberate manipulation of perovskite oxides and the design of functional devices with tailored electronic characteristics.