  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.
