Abstract
An X-ray photoelectron spectroscopy study has been performed on well characterized Bi2Sr2CaCu2 - xCoxOsimilar to 8 (x = 0, 0.02 and 0.1) samples. There is a shift in the Sr binding energy with Co concentration, which is related to the change in T-c. This relationship can be understood by the change of hole concentration in the CuO2 planes as a result of Cobalt doping. The results of Bi 4f and Co 2p core level spectra are also discussed in detail.