Local atomic configuration and Auger valence electron spectra in BiSrCaCuO single crystals

Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub y/ (2212) and Ca-doped Bi/sub 2/Sr/sub 2/CuO/sub y/ (2201) single crystals were systematically investigated by Auger valence electron spectroscopy (AVES). In AVES measurements on two kinds of crystals, a drastic difference was observed in the spectral shape of Ca(2p,3p,3p) reflecting a difference in spin-orbit splitting induced by local atomic configuration in the vicinity of Ca atoms. Furthermore, a Ca(2p,3p,4s) spectrum appeared in both crystals, indicating that the real valence of Ca atoms deviates from +2 in the crystals. The results suggest that AVES is a promising probe for characterizing local atomic configuration and valence electron states of the constituent elements.