EELS and XPS investigations of Ba2Cu3O4Cl2

Electron energy-loss spectroscopy in transmission and x-ray photoelectron spectroscopy have been applied to investigate single crystalline Ba2Cu3O4Cl2 to obtain the loss-function along the high symmetry directions of the cuprate plane, the Cu2p and O1s excitation edges, and to study the valence band and the core level electronic structure. The loss-function shows a gap of 1.65eV; practically dispersionless structures between 2 and 8eV, and a volume plasmon located at 25eV. The dielectric function is derived. The excitation edges are a measure for the number of holes located in the Cu like or O like states parallel or perpendicular to the CU3O4 planes The Cu2p(3/2) XPS shows three features in the main line and a satellite structure due to two independent copper sites and indicating a strong 3d electron correlation. By interpreting forward scattering features the valence band structure can be assigned to its atomic origin.