Intermittent Defect Fluctuations in Oxide Heterostructures.

The heterogeneous nature, local presence, and dynamic evolution of defects typically govern the ionic and electronic properties of a wide variety of functional materials. While the last 50 years have seen considerable efforts into development of new methods to identify the nature of defects in complex materials, such as the perovskite oxides, very little is known about defect dynamics and its influence on the functionality of a material. Here, we  report the discovery of the intermittent behavior of point defects (oxygen vacancies) in oxide heterostructures employing X-ray Photon Correlation Spectroscopy. We  observe local fluctuations between two ordered phases in strained SrCoO with different degrees of stability of the oxygen vacancies. Ab initio-informed phase-field modeling reveals that fluctuations between the competing ordered phases are modulated by the oxygen ion / vacancy interaction energy and epitaxial strain. The results demonstrate how defect dynamics, evidenced by measurement and modeling of their temporal fluctuations, give rise to stochastic properties that now can be fully characterized using coherent x-rays, coupled for the first time to multiscale modeling in functional complex oxide heterostructures. Our  study and its findings open new avenues for engineering the dynamical response of functional materials used in neuromorphic and electrochemical applications. This article is protected by copyright. All rights reserved.