X-Ray photoelectron studies of copper and oxygen states in high-Tc superconducting cuprates

X-ray emission and photoelectron spectra, and the location of fluorine atoms in strontium and calcium copper oxyfluorides

“…XPS Cu 2p spectra measurements of Sr 2 CuO 2 F 2+δ , Sr 1.4 Ba 0.6 CuO 2 F 2+δ , SrCaCuO 2 F 2+δ and Ca 2 CuO 2 F 2+δ compounds are presented in figure 3. Since the binding energies and relative intensities of the Cu 2p 3/2 and Cu 2p 1/2 lines and their satellites are very close to those of various cuprates and CuO [12], it can be concluded that the chemical state of the Cu ions in the oxyfluorides is close to Cu 2+ . Two broadened lines are observed in the XPS O 1s spectra of strontium and calcium copper oxyfluorides (figure 4).…”

“…Two broadened lines are observed in the XPS O 1s spectra of strontium and calcium copper oxyfluorides (figure 4). The most intense O 1s line (E b ∼ 530.8-530.9 eV) is ascribed to O-Cu bonds and the next one at the higher binding energy is due to oxygen of contaminating ZnO, hydroxides and carbonates [12]. The contributions from O-Sr(Ca) bonds (at the lower binding energies) which are seen in XPS O 1s spectra of Bi 2 Sr 2 CaCu 2 O 8+δ [12] are absent in the oxyfluoride O 1s spectra (figure 4), which is in accordance with the structural models for Sr 2 CuO 2 F 2+δ and Ca 2 CuO 2 F 2+δ (figures 1 and 2) in which F atoms not O atoms are located closest to Sr (Ca).…”