Magnetic tunnel contacts to silicon with low-work-function ytterbium nanolayers

Unambiguous proof of spin transport in semiconductor spintronic devices requires a control experiment to exclude spurious signals that arise from the presence of the ferromagnetic contacts. It is shown here that insertion of a low-work-function Yb nanolayer in ferromagnetic tunnel contacts to silicon allows a selective suppression of the tunnel spin polarization for 2 nm of Yb and simultaneous control of the Schottky barrier height. The insertion of a nonmagnetic nanolayer provides a versatile method to exclude artifacts and a solution for nanoscale devices or other geometries in which the frequently employed Hanle effect cannot be applied and a control experiment did not exist.