Epitaxial growth of a full-Heusler alloy Co 2FeSi on silicon by low-temperature molecular beam epitaxy

Abstract

For electrical spin injection and detection of spin-polarized electrons in silicon, we explore highly epitaxial growth of ferromagnetic full-Heusler-alloy Co 2FeSi on silicon substrates using low-temperature molecular beam epitaxy (LT-MBE). Although in -situ reflection high energy electron diffraction images clearly show two-dimensional epitaxial growth for growth temperatures ( T G) of 60, 130, and 200 °C, cross-sectional transmission electron microscopy experiments reveal that there are single-crystal phases other than Heusler alloys near the interface between Co 2FeSi and Si for T G = 130 and 200 °C. On the other hand, almost perfect heterointerfaces are achieved for T G = 60 °C. These results and magnetic measurements indicate that highly epitaxial growth of Co 2FeSi thin films on Si is demonstrated only for T G = 60 °C.