AA bilayer graphene on Si-terminated SiO₂ under electric field

The AA-stacked bilayer graphene/α-SiO₂ (001) interfaces with Si terminated atoms are studied in the presence of an electric field F with different intensities by first principles. AA-stacked bilayer graphene is slightly mis-oriented on SiO₂ substrate without electric field and the band gap is 0.557 eV. However, as F increases, the AA-stacked bilayer graphene has its layers gradually vertically shifted with each other and, finally, transfers into AB-stacked bilayer graphene and the band gap reduces to 0.252 eV under 0.015 Hartree.