Electron emission from individual graphene nanoribbons driven by internal electric field.

Electron emission from individual graphene nanoribbons (GNRs) driven by an internal electric field was studied for the first time inside a high resolution transmission electron microscope equipped with a state-of-art scanning tunneling microscope sample holder with independent twin probes. Electrons were driven out from individual GNRs under an internal driving voltage of less than 3 V with an emission current increasing exponentially with the driving voltage. The emission characteristics were analyzed by taking into account monatomic thickness of GNRs. While deviating from the two-dimensional Richardson equation for thermionic emission, they were well described by the recently proposed by us phonon-assisted electron emission model. Different from widely studied field electron emission from graphene edges, electrons were found to be emitted perpendicularly to the atomic graphene surfaces with an emission density as high as 12.7 A/cm(2). The internally driven electron emission is expected to be less sensitive to the microstructures of an emitter as compared to field emission. The low driving voltage, high emission density, and internal field driving character make the regarded electron emission highly promising for electron source applications.