sp$^{2}$/sp$^{3}$ bonding controlling mechanism at the $\alpha$-Al$_{2}$O$_{3}|$graphene interface

TL;DR

This study uses first-principles calculations to explore how different surface terminations and contact types at the $ ext{Al}_2 ext{O}_3$/graphene interface influence the structural and electronic properties, including $sp^{3}$ bonding and doping effects.

Contribution

It reveals how interface chemistry and surface saturation control $sp^{3}$ bonding, doping, and gap opening in graphene, providing new insights for interface engineering.

Findings

Oxygen contact induces $sp^{3}$ deformation and spin polarization.

Aluminium contact can cause $p$-type doping in graphene.

Surface dangling bonds influence gap opening at the interface.

Abstract

First-principles calculations reported here illuminate the effects of the interfacial properties of $\alpha$-Al$_{2}$O$_{3}$ and graphene, with emphasis on the structural and electronic properties. Various contact interfaces and different $\alpha$-Al$_{2}$O$_{3}$ surface terminations are considered with on and slightly-off stoichiometric aluminium oxide. We show that depending on whether aluminium or oxygen is in contact with graphene, an $sp^{3}$ structural deformation and spontaneous spin-polarization may occur next to the interface contact. Interestingly, some cases cause a $p$-type doping in the graphene band structure, depending on the initial $\alpha$-Al$_{2}$O$_{3}$ geometry placed on graphene. The importance of leaving the surface dangling bonds of alumina saturated or not is also highlighted, and we show that it might be a control mechanism for opening a gap in graphene by the influence of the $sp^{3}$ bond between oxygen and carbon atoms at the interface. We discuss the potential of utilizing this sensitivity for practical applications.