An XPS Study on Hg-Doping Effect on Electronic Structure of BaPb0.75Bi0.25O3Superconductor

The electronic structure of BaPb0.75-xHgxBi0.25O3 (BPHBO) system is studied with x-ray photoemission spectroscopy (XPS). It is found that the core levels of Pb4f and O1s states shift towards low energy with the mercury doping induced, and at the meantime, the core level of Bi4f state shifts towards high energy. The results and analyses reveal that the mercury doping induces a systematic change of the electronic structure of the system, which consequently affects the superconductivity. Accordingly, the suppression of superconductivity at low doping level (x<0.2) is attributed to suppressed charge-disproportionate state whereas the recovery of the superconductivity in the doping level region 0.3