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Cation diffusion and hybridization effects at the Mn-GaSe(0001) interface probed by soft X-ray electron spectroscopies

The electronic properties of the Mn:GaSe interface, produced by evaporating Mn at room temperature on an epsilon-GaSe(0001) single crystal surface, have been studied by soft X-ray spectroscopies. Substitutional effects of Mn replacing Ga cations and Mn-Se hybridization effects are found both in core level and valence band photoemission spectra. The Mn cation valence state is probed by XAS measurements at the Mn L-edge, which indicate that Mn diffuses into the lattice as a Mn2+ cation with negligible crystal field effects. The Mn spectral weight in the valence band is probed by resonant photoemission spectroscopy at the Mn L-edge, which also allowed an estimation of the charge transfer and Mott-Hubbard energies on the basis of impurity-cluster configuration-interaction model of the photoemission process. The charge transfer energy is found to scale with the energy gap of the system. Competing effects of Mn segregation on the surface have been identified, and the transition from the Mn diffusion through the surface to the segregation of metallic layers on the surface has been tracked by core-level photoemission.