X-RAY PHOTOELECTRON DIFFRACTION STUDIES OF BI2SR2CACU2O8+X

A single crystal Bi2Sr2CaCu2O8+x (T0 = 84 K) has been studied by X-ray photoelectron diffraction (XPD). Nearly full-solid-angle intensity distributions of Bi 4f, Sr 3d, Ca 2p, Cu 2p and O 1s emission from a (001)-terminated surface (= c plane) show twofold symmetric patterns with mirror planes along the a and b crystal axes, although the directions of several dominant forward scattering peaks are positioned in a fourfold symmetric way. The results are consistent with the pseudotetragonal structure with a periodically modulated lattice along the b-axis. All diffraction patterns are very different from each other, reflecting the different local geometries around different types of emitter atoms. Basically, the positions of the prominent diffraction peaks are well described by single scattering cluster (SSC) calculations with a tetragonal cluster which is terminated by a Bi-O layer. The discrepancy between the experiment and the simulation gives information about the interlayer mixing of atoms.