Interface composition between Fe{sub 3}O{sub 4} nanoparticles and GaAs for spintronic applications

Recent interest in spintronic applications has necessitated the study of magnetic materials in contact with semiconductor substrates; importantly, the structure and composition of these interfaces can influence both device functionality and the magnetic properties. Nanoscale ferromagnet/semiconductor structures are of particular interest. In this study, the interface structure between a monolayer of ferromagnetic magnetite (Fe{sub 3}O{sub 4}) nanoparticles and a GaAs substrate was studied using cross-sectional transmission electron microscopy techniques. It was found that a continuous amorphous oxide interface layer separates the nanoparticles from the GaAs substrate, and that iron diffused into the interface layer forming a compositional gradient. Electron energy-loss near-edge fine structures of the O K absorption edge revealed that the amorphous oxide is composed of γ-Fe{sub 2}O{sub 3} directly underneath the Fe{sub 3}O{sub 4} nanoparticles, followed by a solid solution of Ga{sub 2}O{sub 3} and FeO and mostly Ga{sub 2}O{sub 3} when approaching the buckled oxide/substrate interface. Real-space density functional theory calculations of the dynamical form factor confirmed the experimental observations. The implication of the findings on the optimization of these structures for spin injection is discussed.