Fe charge state adjustment in ZnO upon ion implantation

The influence of the ion implantation process on the charge state of dilute Fe impurities implanted as radioactive Mn in ZnO is investigated by Fe emission Mössbauer spectroscopy. One sample is additionally implanted with stable Na impurities. Both Fe and Fe charge states are observed, and the Fe /Fe ratio is found to increase with the fluence of both Mn/ Fe and Na ions, demonstrating that the build-up of Fe is not related to the chemical nature of the implanted ions. The results are interpreted in terms of radiation damage induced changes of the Fermi level, and illustrate that the Fe /Fe ratio can be adjusted by ion implantation. The spin-lattice relaxation time for Fe in ZnO is found to be independent of the implantation fluence, and is evidently an intrinsic property of the system. © 2012 IOP Publishing Ltd.