Interface Engineering to Create a Strong Spin Filter Contact to Silicon

TL;DR

This paper demonstrates a novel interface engineering approach that enables the direct epitaxial growth of ferromagnetic EuO on silicon, creating a high-quality spin filter contact crucial for silicon-based spintronics.

Contribution

The study introduces two passivation techniques that prevent interface contamination, allowing for the first time a clean, heteroepitaxial EuO/Si interface without buffer layers.

Findings

Minimized Eu silicide and Si oxide formation to sub-monolayer levels.

Achieved chemically clean, heteroepitaxial EuO/Si(001) interface.

Established a method for creating strong spin filter contacts on silicon.

Abstract

Integrating epitaxial and ferromagnetic Europium Oxide (EuO) directly on silicon is a perfect route to enrich silicon nanotechnology with spin filter functionality. To date, the inherent chemical reactivity between EuO and Si has prevented a heteroepitaxial integration without significant contaminations of the interface with Eu silicides and Si oxides. We present a solution to this long-standing problem by applying two complementary passivation techniques for the reactive EuO/Si interface: ($i$) an $in\:situ$ hydrogen-Si $(001)$ passivation and ($ii$) the application of oxygen-protective Eu monolayers --- without using any additional buffer layers. By careful chemical depth profiling of the oxide-semiconductor interface via hard x-ray photoemission spectroscopy, we show how to systematically minimize both Eu silicide and Si oxide formation to the sub-monolayer regime --- and how to ultimately interface-engineer chemically clean, heteroepitaxial and ferromagnetic EuO/Si $(001)$ in order to create a strong spin filter contact to silicon.