Influence of valence band states on the core hole screening in lanthanide perovskite compounds

Abstract

Investigation on core level and valence band photoelectron spectra of lanthanide perovskite samples (Ag x La1−xCoO3;x<0,3) and reinvestigations of metallic lanthanum and La-oxide layers are reported. Differences in preparation method during perovskite formation are leading to different quality of sample purity and different electronic properties. This could be followed by changes in the density of states near the Fermi energy. On the other hand the screening mechanism after ionization of a La 3d core hole is affected by the relative energy position of occupied valence band states with respect to the empty La 4f* level in the core ionized state. Changes in La 3d line profile are discussed as changes in multi electron processes (e.g. “shake up” or “energy gain”) during photoionization. We attribute the two electron process during photoemission of La 3d electrons to the well screened energy gain transition in LaCoO3, whereas the two electron process results in a shake up transition in La2O3 and La(OH)3.