Trigonal Fe₂Si Nanosheets at Fe/Amorphous SiO_x Interfaces for Spintronic Nanodevices

Abstract

Trigonal Fe 2 Si nanosheets, which are promising candidates for spintronic nanodevices, were synthesized at the Fe/ amorphous (a-)SiO x thin film interface using electron irradiation. The formation of nanoscale silicide was confirmed at 90 K as well as at 298 K. Such a low-temperature synthesis of Fe 2 Si can be attributed to the dissociation of a-SiO x induced by electronic excitation; Si−O bonds dissociate through Auger decay of core− holes generated by electronic excitation, and then, dissociated Si atoms form Fe−Si bonds. The amount of Fe 2 Si formed at room temperature was greater than that at 90 K, suggesting that the atomic migration induced by electronic excitation involves a contribution of thermal energy. The amount of Fe 2 Si nanosheets produced indicates that the Si−O bonds are more easily dissociated by electronic excitation in a-SiO x rather than in a-SiO 2 . Formation of the Fe 2 Si nanosheets found in this study differs from the formation of an equiatomic FeSi phase predicted by thermodynamic models assuming diffusion at a planar Fe/Si interface. We propose a versatile route to selectively form metal silicide nanosheets in an electron irradiated area at temperatures below room temperature.