▎ 摘　　要

Three ways of engineering the bandgap of graphene, i.e., surface bonding, isoelectronic codoping, and alternating electrical/chemical environment, are analyzed with the effective mass approximation and density-functional theory calculations. Surface bonding on graphene would lift its top sigma valence bands above pi valence states, open a sp3 gap, but also bury the linearly dispersive bands into the valence sigma bands. Isoelectronic codoping and asymmetric electrical or chemical environment may open the pi-pi* gap of graphene by breaking its sublattice equivalence. The calculated effective mass versus bandgap may provide useful guidance for the future experimental efforts to fabricate graphene-based semiconductors. (C) 2009 American Institute of Physics. [doi:10.1063/1.3276068]