Mössbauer spectroscopy of Fe in α-AlO following implantation of Mn.

The valence state and annealing reactions of Mn/Fe in single crystalline α-AlO have been determined following low fluence (<10 cm) 60 keV implantations of Mn (T = 1.5 min) and emission Mössbauer spectroscopy on the Fe daughter nuclei in the temperature range from 110-700 K. At 110 K, most probe atoms are found in the Fe state in amorphous surroundings due to the implantation damage. A fraction of the Fe is found in cubic environment, possibly nano-precipitates of η-AlO. This site is found to disappear from the spectra above 500 K. Annealing of the damage sites at increasing temperatures leads first to increased incorporation of the probe atoms as Fe on Al sites, and, above room temperature, also as Fe. The Fe sub-spectrum is masked by slow paramagnetic relaxations following a T dependence, as expected for a two-phonon Raman process. Our data is consistent with data from Co and Fe implantations, suggesting a general increase in the average Fe valence state with lower implantation dose and negligible annealing reactions at room temperature. [ABSTRACT FROM AUTHOR]