Effect of surface treatments, photon and electron impacts on the ceria 3d core level

Abstract We have investigated the effect of surface treatments and damage induced on the Ce3d core level of ceria samples by the X-ray power density, the exposure time to the X-ray beam and the sample charge effect. We show that a CeO 2 surface requires passivation through a mild oxidant exposure such as CO 2 to yield a pure Ce(IV)3d spectrum. Thermal “in vacuo” treatments lead to partial chemical reduction of the surface. Damage induced by the X-ray beam and sample charging produces similar effects. We have studied in more detail the effect of sample charging. We mainly assign these Ce3d core level changes to a photon-stimulated oxygen desorption (PSD) via an Auger interatomic decay. However, owing to the partially reversible character of this effect and to main modifications of the Ce3d final states obtained through hybridization of the Ce4f-O2p states U′ and U″ (V′ and V″, respectively), we propose alternative pathways based on intra-atomic rearrangements or on oxygen migration towards interstitial sites of the fluorite lattice.