Effects of Te- and Fe-doping on the superconducting properties in FeySe1−xTex thin films

Abstract

High quality FeySe1−xTex epitaxial thin films have been fabricated on TiO2-buffered SrTiO3 substrates by pulsed laser deposition technology. There is a significant composition deviation between the nominal target and the thin film. Te doping can affect the Se/Te ratio and Fe content in chemical composition. The superconducting transition temperature Tc is closely related to the chemical composition. Fe vacancies are beneficial for the FeySe1−xTex films to exhibit the higher Tc. A 3D phase diagram is given that the optimize range is x = 0.13–0.15 and y = 0.73–0.78 for FeySe1−xTex films. The anisotropic, effective pining energy, and critical current density for the Fe0.72Se0.94Te0.06, Fe0.76Se0.87Te0.13 and Fe0.91Se0.77Te0.23 films were studied in detail. The scanning transmission electron microscopy images display a regular atomic arrangement at the interfacial structure.