Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

Abstract

We theoretically investigate effect of a transverse electric field generated\nby side gates and a vertical electric field generated by top, back gates on\nenergy bands and transport properties of zigzag bilayer graphene ribbons\n(Bernal stacking). Using atomistic Tight Binding calculations and Green\nfunction formalism we demonstrate that bandgap is opened when either field is\napplied and even enlarged under simultaneous influence of the two fields.\nInterestingly, although vertical electric fields are widely used to control\nbandgap in bilayer graphene, here we show that transverse fields exhibit more\npositive effect in terms of modulating a larger range of bandgap and retaining\ngood electrical conductance. Seebeck effect is also demonstrated to be enhanced\nstrongly about 13 times for a zigzag bilayer graphene ribbons with 16 chain\nlines. These results may motivate new designs of devices made of bilayer\ngraphene ribbons using electric gates.\n