Epitaxial growth of a full-Heusler alloy Co_2FeSi on silicon by low-temperature molecular beam epitaxy

摘要

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℃, 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 ℃. On the other hand, almost perfect heterointerfaces are achieved for T_G = 60 ℃. These results and magnetic measurements indicate that highly epitaxial growth of Co_2FeSi thin films on Si is demonstrated only for T_G = 60 ℃.