We investigate electronic transport in lithographically patterned graphene
ribbon structures where the lateral confinement of charge carriers creates an
energy gap near the charge neutrality point. Individual graphene layers are
contacted with metal electrodes and patterned into ribbons of varying widths
and different crystallographic orientations. The temperature dependent
conductance measurements show larger energy gaps opening for narrower ribbons.
The sizes of these energy gaps are investigated by measuring the conductance in
the non-linear response regime at low temperatures. We find that the energy gap
scales inversely with the ribbon width, thus demonstrating the ability to
engineer the band gap of graphene nanostructures by lithographic processes.Comment: 7 pages including 4 figure