LECTRONIC STRUCTURE STUDIES OF Bi₂Sr₂CaCu_2-xSn_xO_8+\delta SYSTEM

Photoemission measurements have been carried out for Bi₂Sr₂CaCu_2-xSn_xO_8+\delta system with conventional x-ray photoemission spectroscopy for core-level spectra and synchrotron radiation photoemission spectroscopy for valence band. With Sn doping, all core levels shift differently in binding energy, and the intensity near fermi energy becomes smaller in valence hand. From the experiment, we can deduce that the shifts of all core levels and valence hands may involve some other mechanisms, such ms electrostatic effects, in addition to binding energy referencing effects. We argue that the chemical environment plays a crucial role in the electronic structure of high-temperature superconductors.