Structure and Magnetism of Fe Silicides Grown on Si(111) Surfaces

Abstract

We have studied structures and magnetic properties for sevral iron silicides grown on Si(111) 7×7 clean surfaces by solid phase epitaxy method, that is deposition of Fe on the surfaces at room (or low) temperature and subsequent annealing. We also have summarized almost all silicide phases depending on the deposition thickness and the annealing temperature as a schematic phase diagram. We found that some phases show ferromagnetic property arising from interface structures. For the ferromagnetism of the β-FeSi2 phase even at room temperature, the existence of a ferromagnetic silicide (close to Fe3Si) interface layer was pointed out, which leads to a hetero structure of β-FeSi2/Fe-rich silicides/Si(111). For the ferromagnetic property of 2×2-Fe phase at 40 K, the large spin polarization was proposed at the Fe atoms in the B5-type interface structure between the c-FeSi(111) ultra-thin film and the Si(111) substrate. This interface ferromagnetism will extend applications of the spintronic devices.