Bilayer silicene with an electrically-tunable wide band gap

Abstract

Tuning electronic band gaps of materials has proven very challenging, but is fundamentally relevant for optoelectronic applications. We demonstrate that a widely and continuously tunable band gap can be realized in the single-gated bilayer silicene. Bilayer silicene in which 50% of the Si atoms take sp³ hybridization and 50% of the Si atoms do sp²/sp³ hybridization has unusual electronic properties with two Dirac points formed near the Fermi level. Two layers are connected by σ-bonding orbitals. More importantly, we found that the single-gated bilayer silicene could generate a continuously and widely tunable band gap of up to 1.13 eV, which is largely wider than that (0.25 eV) of dual-gated bilayer graphene only at electric displacement fields. This enhanced tuning effect is attributed to dual-polarization of localized π states from the single gated electric field and polarized σ-bonding orbitals of interlayers.