For more practical applications one would like to utilize the strong gate
dependence of graphene for either sensing or transistor applications. Unfortunately,
graphene has no band gap and correspondingly resistivity changes are small.
Therefore, a graphene transistor by its very nature is plagued by a low on/off ratio.
However one way around this limitation, is to carve graphene into narrow ribbons. By
shrinking the ribbon the momentum of charge carriers in the transverse direction
becomes quantized which results in the opening of a band gap.