Chemical Strain Kinetics Induced by Oxygen Surface Exchange in Epitaxial Films Explored by Time-Resolved X-ray Diffraction

Abstract

We have developed a new method to study the oxygen surface exchange kinetics in oxide materials in the form of epitaxial thin films by analyzing subtle cell parameter variations induced by changes in the oxygen stoichiometry of the material. The method consists of continuously analyzing the X-ray diffraction pattern of particular film reflections with a linear X-ray fast detector in a static position, while exposing the sample to sudden changes in the pO2 of the atmosphere at elevated temperatures. With this method, we have been able to follow cell parameter changes as small as 2.10–4 A in time intervals as short as 10 s in La2NiO4+δ epitaxial films and La2NiO4+δ/LaNiO3−δ bilayers. This method provides a simpler and contactless tool for dynamically analyzing oxygen surface exchange kinetics and diffusion in transition metal oxide compounds, and complements other currently used techniques such as Electric Conductivity Relaxation (ECR) and Isotopic Exchange depth profiling (IEDP). In addition, this method i...