DOPING DEPENDENCE OF THE O-1S IS CORE-LEVEL PHOTOEMISSION IN BI-SR-CA-CU-O SUPERCONDUCTORS

The O 1s core level of three different Bi-Sr-Ca-Cu-O superconductors h as been studied by means of high-resolution x-ray-photoelectron spectr oscopy (XPS) and x-ray absorption spectroscopy (XAS). The O 1a XPS spe ctra could be decomposed into three components that were unambiguously assigned to the emission from the three different oxide layers in the crystal structure. These are, in order of increasing binding energy, Cu-O-2, Sr-O, and Bi-O. Furthermore, the component assigned to the Cu- O-2 layers exhibits a shift which depends on the hole doping as monito red by the XAS spectra.