EELS INVESTIGATION OF BI2CUO4 SINGLE-CRYSTALS

The electronic structure of a Bi2CuO4 single crystal is studied by mea ns of Electron Energy Loss Spectroscopy (EELS), at two primary beam en ergies (200 eV and 2 keV). The valence and shallow core electron excit ation regions are investigated and the detected spectral features assi gned, also exploiting the two different probing depths. Beside these r esults, the accidental loss of oxygen induced by a relatively long exp osure of the sample to UV and X radiation, with the subsequent recover y of the oxygen stoichiometry, by exposing the crystal to oxygen atmos phere, allow to identify unambiguously some features in the EEL spectr um of this compound. It is proposed that the loss at 3.6 eV, seen in s ome cuprates, is not detected in Bi2CuO4 because it corresponds to an excitation involving the apical oxygens, not present in this compound.