Electric-field-induced energy gap in few-layer graphene

We provide the first systematic ab initio investigation of the possibility to create a band gap in few-layer graphene (FLG) via a perpendicular electric field. Bernal (ABA) and arbitrarily stacked FLG remain semimetallic, but rhombohedral (ABC) stacked FLG demonstrates a variable band gap. The maximum band gap in ABC stacked FLG decreases with increasing layer number and can be fitted by the relationship Δ_max = 1/(2.378 + 0.521N + 0.035N²) eV. The effective masses of carriers over a wide range around the maximum band gap point in ABC stacked FLG are comparable with that in AB bilayer graphene under zero field. It is therefore possible to fabricate an effective field effect transistor operating at room temperature with high carrier mobility out of ABC stacked FLG.