Surface effects in Mn L3,2 x-ray absorption spectra from (Ga,Mn)As

We have identified a Mn-rich layer on the surface on (Ga,Mn)As thin films which significantly influences soft x-ray absorption measurements. The Mn L-3,L-2 x-ray absorption spectra of the untreated films show a strong multiplet structure, consistent with earlier observations and characteristic of MnO. After removal of the surface layer, the multiplet structure is less pronounced and the spectrum is shifted to similar to0.5 eV lower photon energy. Comparison with calculated spectra imply a localized Mn ground state for the untreated sample and a hybridized ground state after etching. In addition, a large x-ray magnetic circular dichroism is observed at the Mn L-3,L-2 edge in the etched film. These results may explain several peculiarities of previously reported x-ray absorption studies from (Ga,Mn)As. (C) 2004 American Institute of Physics.