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

Abstract

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.