Silicon passivation of zigzag graphene edge enabling robust spin-polarized nanogap quantum transport

Zigzag graphene edges (ZGEs) can ideally host spin-polarized edge states, providing significant potential for spintronics applications. However, because the high chemical reactivity of a pure sp² termination easily destabilizes zigzag edges, preparing well-defined ZGEs at ambient conditions remains a formidable practical challenge. Performing first-principles calculations, we herein demonstrate that the silicon passivation of ZGEs is a reliable method to preserve the spin-polarized ZGE states and furthermore to improve their electronic connectivity with neighboring nanostructures. We find that the desired structural stabilization is driven by the formation of polysilene-like quasi-one-dimensional puckered silicon chain configurations along the ZGE, which satisfies both the strong propensity of silicon atoms toward the sp³-type bonding and the preservation of the sp²-type graphene C edge structure. Calculating the quantum tunneling across DNA nucleobase located in a nanogap between two Si-passivated ZGEs, we finally demonstrate that silicon passivation expands the ZGE electron transport channels both spatially and energetically and significantly enhances spin-polarized sensing currents. We find that 8-oxo-guanine accommodates very large spin-polarized currents due to the hybridization of the spin-polarized reactive oxygen atom and ZGE orbitals, providing an intriguing possibility of the quantum-mechanical sensing of oxidatively damaged DNA.