PNNL

Abstract

Irradiation damage of oxide materials is complicated by the presence of interfaces, which can serve as either defect sinks or defect accumulation sites; the radiation response depends on factors such as interfacial structure, chemistry, and termination. We have characterized the response of epitaxial Fe3O4(111) / Cr2O3(0001) thin film heterostructures to 400 keV Ar2+ radiation at room temperature. The density of misfit dislocations in both the Fe3O4 overlayer and Cr2O3 buffer layer is varied by changing the thickness of Cr2O3 to be pseudomorphically strained to the Al2O3 (0001) substrate (5 nm thick), or partially relaxed (20 nm thick), as confirmed by Bragg filtering analysis of scanning transmission electron microscopy images. In both cases, irradiation leads to damage accumulation on the Fe3O4 side of the heterointerface, as shown by Rutherford backscattering spectrometry measurements in the channeling geometry. However, the interface with more misfit dislocations exhibits damage accumulation at a faster rate than the less-defective interface. Likewise, layer-resolved electron energy loss spectroscopy reveals interfacial reduction of Fe after irradiation at the more defective interface. Intermixing of Cr across the interface is observed by atom probe tomography, which is likely facilitated by the generation of Cr interstitials in Cr2O3 under irradiation.