Oxygen 1s and cobalt 2p X-ray absorption of cobalt oxides

Abstract

The oxygen 1s and cobalt 2p X-ray absorption spectra of CoO, Li-doped CoO and LiCoO₂ have been measured with 0.1 eV resolution. The cobalt 2p spectra are analysed with a ligand-field multiplet model and the inclusion of chase-transfer effects is discussed. The oxygen 1s spectra are interpreted as transitions to empty oxygen p states and it is concluded that the effects of correlations in the 3d band possibly are too small to be detectable. The symmetries and the electronic configurations of the cobalt ions in the oxides are determined. It is concluded that, in contrast to for example NiO and La₂CuO₄, the doping-induced states are possibly of ¹A₁ symmetry, which would imply that the quasi-particles have spin ³/₂ and are most likely trapped.