Effect of thermal annealing on the average and local structure of superconducting polycrystalline NbRe films

NbxRe1−x is a non-centrosymmetric superconductor recently realized in thin film form. The access to the basic physics that governs this material is hindered by the polycrystalline structure of the films which consist of grains of small dimensions. In these conditions, films are not decisive in revealing the nature of the superconducting order parameter, and, in particular, the possible presence of a spin-triplet component. In this work, post-deposition annealing procedures were performed to improve the crystalline quality of the as-grown films. As determined by X-ray diffraction measurements, by tuning the annealing process, it was possible to increase the crystalline size from 1-2 nm up to several nanometers. Pair distribution function analyses revealed the non-centrosymmetric crystal structure of the treated NbRe films. Finally, electrical transport measurements, performed to study the relationship between structural and transport properties of the samples, showed a reduction of the superconducting critical temperature after the thermal treatment, which can be reasonably ascribed to oxygen contamination. These, results will be useful to realize films for future experiments meant to access nature of the superconducting order parameter.