A photoemission study of Na-induced hole doping in Bi2Sr2-y(Na-y)Ca1-x(Na-x)Cu2O8+delta

An X-ray photoelectron spectroscopy study of Na-doped Bi-2212 cuprates is reported. Core level photoemission spectra were collected, at different take-off angles, from a monophasic crystal. The results of the lineshape analysis and the dependence of the core line intensity on the analyser take-off angle allowed us to rule out the presence of Na within the Bi-O layers, indicating that Na+ is very likely replacing Ca2+ or Si2+ ions.