  This study demonstrates that the nanopore terraces constructed on a
multilayer graphene sheet could be employed to con-trol the conformation and
transportation of an ssDNA for nanopore sequencing. As adsorbed on a terraced
graphene na-nopore, the ssDNA has no in-plane swing nearby the nanopore, and
can be locked on graphene terraces in a stretched con-formation. Under biasing,
the accumulated ions near the nanopore promote the translocation of the locked
ssDNA, and also disturb the balance between the driven force and resistance
force acted on the nucleotide in pore. A critical force is found to be
necessary in trigging the kickoff of the ssDNA translocation, implying an
inherent field effect of the terraced graphene nanopore. By changing the
intensities of electric field as trigger signal, the stop and go of an ssDNA in
the nanopore are manipulated at single nucleobase level. The velocity of ssDNA
in the nanopore can also be regulated by the frequency of the
electro-stimulations. As a result, a new scheme of controllable translocation
of ssDNA in graphene nanopores is realized by introducing controllers and
triggers, appealing more explorations in experiment.
