Modulation of bandgap in bilayer armchair graphene ribbons by tuning vertical and transverse electric fields

• Published in: Superlattices and microstructures 2017-02, Vol.102, p.451-458
• Main Authors: Vu, Thanh-Tra, Nguyen, Thi-Kim-Quyen, Huynh, Anh-Huy, Phan, Thi-Kim-Loan, Tran, Van-Truong
• Format: Article
• Language: English
• ISSN: 0749-6036; 1096-3677
• DOI: 10.1016/j.spmi.2016.12.031

We investigate the effects of external electric fields on the electronic properties of bilayer armchair graphene nano-ribbons. Using atomistic simulations with Tight Binding calculations and the Non-equilibrium Green's function formalism, we demonstrate that (i) in semi-metallic structures, vertical fields impact more effectively than transverse fields in terms of opening larger bandgap, showing a contrary phenomenon compared to that demonstrated in previous studies in bilayer zigzag graphene nano-ribbons; (ii) in some semiconducting structures, if transverse fields just show usual effects as in single layer armchair graphene nano-ribbons where the bandgap is suppressed when varying the applied potential, vertical fields exhibit an anomalous phenomenon that the bandgap can be enlarged, i.e., for a structure of width of 16 dimer lines, the bandgap increases from 0.255 eV to the maximum value of 0.40 eV when a vertical bias equates 0.96 V applied. Although the combined effect of two fields does not enlarge the bandgap as found in bilayer zigzag graphene nano-ribbons, it shows that the mutual effect can be useful to reduce faster the bandgap in semiconducting bilayer armchair graphene nano-ribbons. These results are important to fully understand the effects of electric fields on bilayer graphene nano-ribbons (AB stacking) and also suggest appropriate uses of electric gates with different edge orientations. •The effects of transverse and vertical electric fields on bilayer armchair graphene ribbons were studied.•The vertical fields exhibit more effectively than the transverse ones in terms of opening larger bandgap in semi-metallic structures.•An anomalous phenomenon was observed under the effect of the vertical fields on semi-conducting structures.•The combination of the two fields can be useful to reduce the bandgap more rapidly.