Reversible Mn valence state switching in submicron α-AlO:Mn by soft X-rays and blue light - a potential pathway towards multilevel optical data storage.

The generation of Mn in α-AlO:Mn by soft X-ray exposure is demonstrated with a large dynamic range of the X-ray generated Mn luminescence signal, indicating the potential use of α-AlO:Mn for multilevel optical data storage. Samples with a range of Mn concentrations (0.05, 0.1, 0.2, 0.4, 0.6 and 1.2 atom%) were prepared a facile combustion method and the sample with 0.4 atom% was found to display the highest luminescence intensity. The stored information can be read out the -lines (E → A) under ∼470 nm (A → T), or ∼630 nm (A → T) excitation with the latter being preferred since photobleaching is minimized. Interestingly, the Mn valence state can be fully switched back to Mn by blue light exposure (, 462 nm laser diode). The stored information could be repeatedly written and erased, showing no significant deterioration over five consecutive cycles, with less than 5% uncertainty.