Abstract
Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics.
Highlights
As metals are ineffective injectors, a number of alternatives have been proposed
Spin injection technologies based on insulating tunnel barriers are plagued by high contact resistance at the interface: the generation of spin MOSFETs would require a drastic reduction of the resistance between source and drain
We report a novel technology for integration of functional oxides with silicon which solves the long-standing problem of direct epitaxial growth of the EuO/Si structure
Summary
Integration of ionic functional oxides with covalent Si is always challenging but an epitaxial growth of EuO directly on Si faces additional difficulties. Silicide regions and a non-crystalline layer at the interface are detected by high-resolution TEM for EuO grown on H-passivated silicon[36] Both approaches suggested so far – Si surface passivation either by the 1 × 2 metal-based superstructure or by hydrogen – do not solve the problem of the formation of the direct EuO/Si contact. Electron microscopy reveals an atomically abrupt EuO/Si interface This quantum leap in the quality of EuO films comes from interface engineering – the first monolayer is formed by the 1 × 5 metal superstructure instead of the standard 1 × 2 reconstruction. We hope that this breakthrough in the material engineering will be followed by a successful spin injection through the manufactured spin contact
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