EELS INVESTIGATION OF BI2CUO4 SINGLE-CRYSTALS

The electronic structure of a Bi2CuO4 single crystal is studied by means of Electron Energy Loss Spectroscopy (EELS), at two primary beam energies (200 eV and 2 keV). The valence and shallow core electron excitation regions are investigated and the detected spectral features assigned, also exploiting the two different probing depths. Beside these results, the accidental loss of oxygen induced by a relatively long exposure of the sample to UV and X radiation, with the subsequent recovery of the oxygen stoichiometry, by exposing the crystal to oxygen atmosphere, allow to identify unambiguously some features in the EEL spectrum of this compound. It is proposed that the loss at 3.6 eV, seen in some cuprates, is not detected in Bi2CuO4 because it corresponds to an excitation involving the apical oxygens, not present in this compound.