We present the results of the electronic band structure study of Ge_0.9Mn_0.1Te epitaxial layer surface, clean and enriched in Mn by in situ deposition. GeMnTe is a ferromagnet with a relatively high Curie temperature (up to 140 K) strongly dependent on Mn concentration.

The Ge_0.9Mn_0.1Te layers were grown on BaF₂ (111) substrates by an MBE method with use of GeTe, Te₂ and Mn solid sources, at the substrate temperature of 450^oC. The sample surface was protected against interaction with ambient atmosphere (during transfer to the photoelectron spectrometer) by a layer of amorphous tellurium. Prior the photoemission experiments, the tellurium layer was removed by sputtering and annealing. The Mn overlayers were deposited in situ at room temperature.

The valence band and shallow core levels of Mn/Ge_0.9Mn_0.1Te were investigated by means of resonant photoemission spectroscopy. This experimental technique is a tool enabling determination of the emission of electrons from the transition metal 3d orbitals. Therefore, the sets of photoemission spectra were measured for the photon energy range covering the energy of the Mn 3p®3d transition. They were acquired for the clean surface of Ge_0.9Mn_0.1Te sample, after evaporation of 0.5 ML Mn and after annealing. The annealing was carried out in order to induce the diffusion of Mn atoms into the Ge_0.9Mn_0.1Te crystal. The Mn 3d states contribution occurred in the upper part of the valence band, with a maximum at the binding energy of about 4 eV. The shape of the spectra corresponds to the emission from Mn ions occupying the lattice sites with octahedral coordination. Deposition of Mn and annealing the system lead to an increase of Mn 3d feature intensity. This proves that diffusing Mn ions occupy the same sites in the lattice as those introduced during the layer growth, increasing the Mn contents in the subsurface layer.

We acknowledge support by MSHE (Poland) grants N202 101 31/0749 and 1 P03 B053 26.