Spin-asymmetric graphene nanoribbons in graphane on silicon dioxide

TL;DR

This study investigates spin-asymmetric properties of graphene nanoribbons on a silicon dioxide substrate, revealing how substrate-induced charge imbalance causes spin degeneracy breaking and band gap variations.

Contribution

It demonstrates the stability of one-sided hydrogenation on graphene and shows how substrate interactions induce spin asymmetry in graphene nanoribbons.

Findings

Asymmetric hydrogenation is stable on graphene.

Substrate causes spin degeneracy breaking in nanoribbons.

Different band gaps emerge for opposite spins due to substrate effects.

Abstract

Hydrogenated graphene, graphane, is studied on oxygen-terminated silicon dioxide substrate using ab initio calculations. A structure with hydrogenation only on one side of the graphene layer is found stable and its hydrogen configurations are presented. Additionally, we form zigzag graphene nanoribbons by selectively removing hydrogens from the epitaxial graphane layer. In these ribbons, the spin degeneracy of the freestanding antiferromagnetic zigzag ribbons is broken, and band gaps of different magnitude emerge for the opposite spin species. This degeneracy breaking is due to a charge imbalance in the substrate below the ribbon, introduced through the asymmetric alignment of the substrate atoms with respect to the edges of the graphene ribbon.