Field emission from dense graphene edges in mechanical pencil lead rods

Graphene edges are densely arranged on the cross section of carbonized mechanical pencil lead rods. In this paper, we demonstrate that the lead rods give superior field emission (FE) characteristics, i.e., high emission currents with high stability at low macroscopic electric fields, even though the rods are not sharpened. The FIM/FEM images suggest that emission sites are the graphene edges. The FE characteristic remains similar even after removing the micrometer-scale protrusions, indicating that the superior FE characteristics are responsible for electronic properties or nm-scale features of the emitter material, not for the μm-scale features giving high field enhancement factors. This is consistent with the theoretical expectation that the electric field is not shielded at the graphene ribbon edges. The obtained results may give a clue to clarify the mechanism of low macroscopic field (LMF) emission from carbon-related materials.