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 (T_c) 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.