Satellite structure in the photoemission spectra of MnO(100)

The satellite structure in both core-level and valence-band photoemission spectra from single-crystal MnO(100) has been studied by using both x-ray photoemission spectra and resonant photoemission. Only very weak satellites are present in the Mn 2p core-level spectra, while no satellite structure is evident in the Mn 3p and 3s core-level spectra. The small intensity of the satellite peaks in MnO is consistent with the trend predicted by a recent ligand charge-transfer screening model; such screening is quite weak in MnO in comparison to the heavier transition-metal oxides. The valence-band spectrum, however, exhibits a stronger satellite peak than predicted by the model, and its origin has been uncertain. We have found that, while the satellite in the valence-band spectrum can be resonantly enhanced across the Mn 3p{→}3d optical excitation threshold, its intensity depends strongly upon surface treatment. The satellite disappears with only 0.2--1-langmuir exposure of oxygen at 340 ^∘{}C, confirming that it is essentially a surface-related feature. We suggest that it is associated with point defects on the surface, presumably surface Mn vacancies.