Effect of Oxygen Defect Concentrations in Oxide Thin Films on the Stress State, and Hetero-Interface-Controlled Thin Films with Novel Properties

We study the effect of strain on the defect concentration in oxide thin films such as Pr-doped ceria. In particular, we use temperature-varied X-ray diffraction measurements to study microstructural and thermomechanical properties in these nanocrystalline materials. In addition, we have developed a novel focused ion beam-based technique to section layered materials and study the properties of heterointerfaces. Interface-driven properties commonly begin to dominate over bulk properties as the multilayer dimensions approach nanometer dimensions. A key challenge is how to directly extract properties that are confined to these interfaces while retaining the integrity of the overall structure. While scanning probe methods, in principle, offer the requisite high spatial resolution, there have been challenges in successfully applying these methods to obtain information representative of the structural and electronic states of oxide superlattices. With our new method, we demonstrate how such buried interlayers within complex oxide multilayers can be exposed to ambient conditions by focused ion-beam (FIB) milling, by employing a small incidence angle between the specimen surface and the ion beam. The advantages of this novel method include the capability for directly exposing the interfaces of a multilayer system in a geometry feasible for scanning probe measurements, and the capability for controlling the vertical and lateral dimensions and crystallographic orientations of the layers so exposed.