Oxygen crystallographic positions in thin films by non-destructive resonant elastic X-ray scattering

Abstract

Precisely locating oxygen atoms in nanosized systems is a real challenge. The traditional strategies used for bulk samples fail at probing samples with much less matter. Resonant elastic X-ray scattering (REXS) experiments in the X-ray absorption near-edge structure (XANES) domain have already proved their efficiency in probing transition metal cations in thin films, but it is not feasible to perform such experiments at the low-energy edges of lighter atoms – such as oxygen. In this study, the adequacy of using REXS in the extended X-ray absorption fine structure (EXAFS) domain, also known as extended diffraction absorption fine structure (EDAFS), to solve this issue is shown. The technique has been validated on a bulk FeV2O4 sample, through comparison with results obtained with conventional X-ray diffraction measurements. Subsequently, the positions of oxygen atoms in a thin film were unveiled by using the same strategy. The approach described in this study can henceforth be applied to solve the crystallographic structure of oxides, and will help in better understanding the properties and functionalities which are dictated by the positions of the oxygen atoms in functional nanosized materials.

inserexs: reflection choice software for resonant elastic X-ray scattering

“…Three examples are given in this section. They are analogous to the study we carried out on FeV 2 O 4 (Pen ˜a Corredor et al, 2022), in which both the experimental and the theoretical spectra were shown. In the structures presented hereafter, the studied parameter directly affects the material properties, and the best reflections to study such parameters are plotted in a sensitivity versus intensity plot.…”

“…Beyond this edge, by scanning the extended X-ray absorption fine structure (EXAFS; 50-1000 eV above the edge), also known as extended diffraction absorption fine structure (EDAFS), we can obtain information about the chemical environment (Poineau et al, 2019). In thin films, DANES has already been used to study cation oxidation states and their occupation factors (Lefevre et al, 2017), and we have recently shown that EDAFS can be successfully used to indirectly locate the ligands of the cation (Pen ˜a Corredor et al, 2022).…”