Structural coupling across the direct EuO/Si interface.

The ferromagnetic semiconductor EuO is believed to be an effective spin injector when directly integrated with silicon (Si). Injection through spin-selective ohmic contact requires superb structural quality of the interface EuO/Si. A recent breakthrough in manufacturing free-of-buffer-layer EuO/Si junctions calls for structural studies of the interface between the semiconductors. The synthesis of EuO employs an advanced protection of the Si substrate surface and a two-step growth protocol. It prevents unwanted chemical reactions at the interface. Ex situ high-resolution x-ray diffraction (XRD) and reflectivity (XRR) accompanied by in situ reflection high-energy electron diffraction reveal direct coupling at the interface. A combined analysis of XRD and XRR data provides a common structural model. The structural quality of the EuO/Si spin contact far exceeds that of previous reports and thus makes a step forward to the ultimate goals of spintronics.