Stability of the Fe³⁺ state in ZnO

We have applied implantation of radioactive Mn (T = 1. 5 min) at the ISOLDE facility at CERN with 50-60 keV energy to fluences <10 /cm to study the emission Mössbauer spectra from the 14. 4 keV transition of the Fe daughter atoms. For fluences >=5 × 10Mn/cm, the spectra are dominated by the Fe state exhibiting a slow paramagnetic relaxation. We show that the Fe state in ZnO saturated by <10Mn/cm implantations is unstable. The crystals can be reset by annealing at T > 760 K or storage at room temperature for 12 months, after which they show dominantly the Fe state for <2 × 10Mn/cm implantations. These findings are discussed in terms of diffusion and/or annihilation of implantation-induced defects. © 2012 Springer Science+Business Media Dordrecht.