  Realization of logic circuits in graphene with an energy gap (EG) remains one
of the main challenges for graphene electronics. We found that large transport
EGs (>100 meV) can be fulfilled in dual-gated bilayer graphene underneath a
simple alumina passivation top gate stack, which directly contacts the graphene
channels without an inserted buffer layer. With the presence of EGs, the
electrical properties of the graphene transistors are significantly enhanced,
as manifested by enhanced on/off current ratio, subthreshold slope and current
saturation. For the first time, complementary-like semiconducting logic
graphene inverters are demonstrated that show a large improvement over their
metallic counterparts. This result may open the way for logic applications of
gap-engineered graphene.
