The fabrication of high-quality superconducting FeSe1−xSx films via pulsed laser deposition

Abstract

Due to its unique properties, FeSe1−xSx superconductors have been prime candidates to investigate the unconventional superconducting mechanism in iron chalcogenides. In this study, we report the successful preparation of high-quality epitaxial FeSe1−xSx films with x ≤ 0.4 on different substrates via pulsed laser deposition. With different S content, it is found that CaF2 (100) single crystal is the most preferable substrate to use to grow superconducting FeSe1−xSx films. With the increment of S content, the nematic transition temperature (Ts) of FeSe1−xSx films decreases simultaneously and disappears at x ≈ 0.2. In contrast to FeSe1−xTex films, the superconducting transition temperature (Tc) of FeSe1−xSx films decreases continuously with S doping. And the Tc shows no enhancement after the disappearance of Ts, suggesting that the nematic transition does not positively impact the superconductivity in these films. In addition to the influence of different S content, it is found that the non-negligible in-plane tensile strain originating mostly from the mismatch between the FeSe1−xSx films and the substrate is the key factor suppressing the superconductivity. Our work can provide constructive guidance for preparing superconducting FeSe1−xSx films and gives a further understanding of the interplay of Ts, strain, and superconductivity in iron-chalcogenide films.