Incorporation Site and Valence State of Sn Atoms in Sn-Substituted La(O,F)BiS2 Superconductor

BiS2-based superconductors have attracted considerable attention owing to the possible occurrence of exotic superconductivity. Recently, the superconducting critical temperature (Tc) of La(O,F)BiS2 has been reported to be enhanced with Pb or Sn doping. In this study, we have performed photoelectron holography (PEH) and core-level photoelectron spectroscopy (PES) to clarify the substituted site and valence state of Sn atoms in Sn-substituted La(O,F)BiS2. The PEH study revealed that the Sn atoms are incorporated into the Bi sites. A core-level PES study suggested that the valence state of the substituted Sn atoms is close to that of Sn2+, indicating that the Sn dopants provide hole carriers that compensate the electron carriers introduced by the F doping. These results are fundamental information for understanding the impact of Sn doping on this compound.