Radiation Damage in Iron Oxides upon Fe Ion Implantation

Abstract

To investigate radiation-induced damage, Fe ions with an energy of 5.6 MeV and a fluence of 10¹⁵ cm^–2 were implanted into two iron oxides: hematite Fe₂O₃ and magnetite Fe₃O₄. Conversion electron Mössbauer spectra, Raman spectra, and data from electron and atomic force microscopy were obtained for the irradiated surfaces, as well as after removal of a surface layer with a thickness of 1 μm. Irradiation affected the Mössbauer spectra of hematite and magnetite in different ways. In hematite, an additional H₂ sextet was formed, corresponding to defect Fe sites. In magnetite, irradiation caused only line broadening of the B sextet. The study concludes that the spinel structure of Fe₃O₄ is more resistant to irradiation effects. In the center of the Mössbauer spectra of both oxides, quadrupole doublets corresponding to the Fe²⁺ phase were observed before polishing. The formation of this phase is interpreted within the thermal spike model as a result of material quenching in the ion track region. According to electron and atomic force microscopy data, after polishing to a depth of approximately 1 μm, a sharp increase in surface roughness was observed, with the formation of pits up to 300 nm deep. The destruction of the subsurface layer is evidently caused by a high concentration of radiation-induced defects, which form regions of large stress, leading to crack formation and loss of layer continuity.