Atomic-scale EDS Mapping for Chemical Imaging and Quantification of Interdiffusion in Self-assembled Vertically Aligned Nanocomposite Thin Films

Abstract

Recent technical advances in scanning transmission electron microscopy (STEM) and xray detector technology have made it possible to perform atomic-resolution chemical mapping using energy-dispersive x-ray spectroscopy (EDS) [1]. This ability allows for establishing a direct correlation between atomic-scale STEM images, such as high-angle annular dark-field (HAADF) images, and atomic-scale chemical EDS images, making chemical quantification of interfaces, defects and crystalline structure at the atomic-scale possible. Using these capabilities, we have lately quantified the chemical composition of an epitaxial (La0.7Sr0.3)MnO3 (LSMO)/BiFeO3 (BFO) quantum structure [2], cation occupancy in a Sm-doped SrTiO3 (STO) thin film and antiphase boundaries present within STO films [3], as well as determined structures of several intermetallic alloys [4]. In this study, we describe further use of these capabilities to quantify atomic-scale interdiffusion in self-assembled, vertically aligned nanocomposite (VAN) thin films. Self-assembled VAN thin films, consisting of two immiscible components heteroepitaxially grown on single crystals, have experienced an increase in research activity in recent years [5]. These structures offer the advantage of utilizing the functionalities of both components with the possibility of tuning the material’s properties by tailoring the volume ratio of the two components, the interface-to-volume ratio and hetero-epitaxial strain. In addition, modification of interface properties such as structural and elemental distribution across the interface offers an additional dimension to generate new properties and functionalities. The atomic-scale characterization of the interface plays an essential role in understanding the structure-property relationships. Here we describe the characterization of NiO:LSMO and ZnO:LSMO VAN thin