Structure and bonding of bi-sr-ca-cu-o crystal by x-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy was performed on high-Tc superconducting Bi-Sr-Ca-Cu-O single crystals with Tc~80 K. The core-level electron spectra of Sr, Ca, and Bi show the possibility of exchanging their lattice sites in the crystal. On the other hand, the core-level electron spectrum of Cu indicates a unique lattice site in the crystal. These features are consistent with the structure model for the crystal with formula unit Bi₂(Sr,Ca)₃Cu₂Oy. We can readily determine the distribution of Sr, Ca, and Bi in the cation sites by x-ray photoelectron spectroscopy in contrast to x-ray diffraction and high-resolution transmission electron microscopy.