Post-annealing effect on the electronic structure of Mn atoms in Ga _1-xMn_xAs probed by resonant inelastic x-ray scattering

The electronic structure of as-grown and post-annealed Ga _1-xMn_xAs epilayers (x≈0.055) has been investigated using resonant inelastic x-ray scattering. Mn L_2,3 x-ray emission spectra show that the integral intensity ratio of Mn L₂ to L ₃ emission lines increases with annealing temperature and comes close to that of manganese oxide. The oxygen K-emission/absorption spectra of post-annealed Ga_0.945Mn_0.055As show 1.5-3.0 times higher degree of oxidation on the film surface than that of the as-grown sample. These experimental findings are attributed to the diffusion of Mn impurity atoms from interstitial positions in the GaAs host lattice to the surface where they are passivated by oxygen.