Epitaxial Fe Thin Films on {100} Y2Ti2O7: Model Interfaces for Nano-Oxide Dispersion Strengthened Steels

Abstract

Nanostructured Ferritic Alloys, a variant of oxide dispersion strengthened steels, contain a high density of ≈2.5 nm Y-Ti-O nano-oxides (NOs) that provide remarkable irradiation tolerance, enhance recombination of vacancies and self-interstitial irradiation defects, and trap He in fine-scale bubbles at their interfaces. To complement studies of embedded NOs, mesoscopic-scale metal-oxide interfaces were fabricated by electron beam deposition of Fe films on {100} Y2Ti2O7 (YTO) bulk single-crystal substrates. We report, for the first time, the dominant epitaxial orientation relationship (OR) for the polycrystalline Fe film: {110}Fe\\{100}YTO and 〈111〉Fe\\〈110〉YTO. Further, one large grain region had an OR that is also found in embedded NOs: {100}Fe\\{100}YTO and 〈100〉Fe\\〈110〉YTO. HRTEM studies show clean, semicoherent interfaces with misfit dislocation spacings of 0.7 and 1.4 nm, respectively. These observations are important for the development of first principles models of metal-oxide interfaces, and the bilayers themselves will be used to observe the He partitioning between the Fe, YTO, and the corresponding interface.