Epitaxial Growth of a Full-Heusler Alloy Co$_{2}$FeSi on Silicon by Low-Temperature Molecular Beam Epitaxy

TL;DR

This study demonstrates the successful epitaxial growth of Co2FeSi full-Heusler alloy thin films on silicon substrates at low temperature, which is promising for spintronic applications involving silicon.

Contribution

It shows that high-quality epitaxial Co2FeSi films can be grown on silicon at low temperature (60°C) using molecular beam epitaxy, with nearly perfect interfaces.

Findings

Epitaxial growth confirmed by RHEED at all tested temperatures.

Single-crystal phases other than Heusler alloys appear at higher growth temperatures.

High-quality epitaxial films with nearly perfect interfaces are achieved at 60°C.

Abstract

For electrical spin injection and detection of spin-polarized electrons in silicon, we explore highly epitaxial growth of ferromagnetic full-Heusler-alloy Co2FeSi thin films on silicon substrates using low-temperature molecular beam epitaxy (LTMBE). 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.