▎ 摘　　要

We report density functional theory band structure calculations of graphene doped with group IV elements. A bandgap as high as 2.13 eV is calculated for a single layer of graphene doped with Si while Ge and Sn doping reduce this bandgap for equal doping concentrations. Bilayers of doped graphene are also studied and it is found that the bandgap of these materials is less than that of the single layer counterparts. Finally, a transverse electric field is applied to the doped bilayers and it is found that the bandgap is inversely proportional to the electric field strength in contrast to what has been observed in the case of pristine bilayers. Carrier effective masses were calculated and in general the effective masses of electrons and holes are found to be similar. (C) 2013 AIP Publishing LLC.