An Ab Initio Study on Energy Gap of Bilayer Graphene Nanoribbons with   Armchair Edges
  Dependency of energy bandgap (Eg) of bilayer armchair graphene nanoribbons (AGNRB) on their widths, interlayer distance (D) and edge doping concentration of boron/nitrogen is investigated using local density approximation and compare to the results of monolayer graphene nanoribbons (AGNRM). Although Eg of AGNRB, in general, is smaller than that of AGNRM, AGNRB exhibits two distinct groups, metal and semiconductor, while AGNRM displays purely semiconducting behavior. Eg of AGNRB, moreover, is highly sensitive to D, indicating a possible application in tuning Eg by varying D. Finally, edge doping of both AGNR systems reduces Eg by 11-17%/4-10% for AGNRM/AGNRB, respectively. 
Kai-Tak Lam and Gengchiau Liang