Strongly (001)-textured MgO/Co40Fe40B20 spin-tunnel contact on n-Ge(001) and its spin accumulation: Structural modification with ultrathin Mg insertion by sputtering

Abstract The sputter-deposited fcc-MgO (001)[100]/bcc-Co 40 Fe 40 B 20 (001)[110] spin-tunnel contact (STC) was successfully prepared on n-Ge(001). We found that the interfacial modification by ultrathin (6 Å) Mg insertion at the interface between n-Ge and MgO plays an important role in spin injection into Ge. The significantly amplified spin accumulation was observed in this STC as a result of the structural modification. The three-terminal Hanle signal of this STC was 2.7 times larger than that of the STC without Mg insertion. Our study confirms that a sputtering technique is indeed practical and useful to modify interfacial structures for the efficient injection of spins into semiconductors.