A Comparative Photoemission Study of Ceria and Gold-doped Ceria /Cu(111) Interfaces

We have studied the electronic states in three different ceria thin film surfaces prepared on a Cu(111) single-crystal surface by vapor deposition at different conditions: at 250 °C, at room temperature and finally Au-doped ceria film obtained by simultaneous deposition of Au and CeO2 at room temperature (RT). Electronic properties of the layers and interaction of gold with CeO2 were investigated with use of synchrotron-radiation-excited PES and resonant photoemission (Ce 4d → 4f transitions). We have observed partial Ce → Ce reduction induced by decrease of deposition temperature to RT instead 250 °C and also by doping ceria by gold, accompanied by a 4f resonance enhancement of the Ce species. In the case of Audoped sample the surface reduction degree is stronger and can be explained by the possible creation of new ionic Au state peaks observed in the Au 4f spectra.