Influence of Al co-deposition on the crystal growth of Co-based Heusler-compound thin films on Si(111)

For spintronic applications compatible with silicon (Si) large scale integrated circuits, we have so far developed the growth technique of a Co-based Heusler-compound film, Co2FeSi, on Si by using low-temperature molecular beam epitaxy. In this study, we explore an addition technique of a fourth element, Al, to the Co2FeSi films in order to tune the number of the valence electrons and to realize the high-performance spintronic devices. We can demonstrate L21-ordered Co2FeSi0.5Al0.5 films using Al co-deposition although 4-nm-thick reaction layers are formed at the interface. A possible mechanism of the epitaxial growth of quaternary Co2FeSi1−xAlx films on Si is discussed.