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

摘要

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 (T-s) of FeSe1-xSx films decreases simultaneously and disappears at x 0.2. In contrast to FeSe1-xTex films, the superconducting transition temperature (T-c) of FeSe1-xSx films decreases continuously with S doping. And the T-c shows no enhancement after the disappearance of T-s, 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 T-s, strain, and superconductivity in iron-chalcogenide films.