Field emission from vertically aligned graphene edges at the apex of the pencil lead

We demonstrated a stable and efficient field electron emission from vertically aligned graphene edges at the apex of the graphitized pencil lead (PL). We found that the electron emission pattern from PL observed with Field Emission Microscope (FEM) was dominated by the "dragonfly patterns" that are characteristic of the graphene edge, clearly suggesting the presence of the graphene edges with nearly vertical alignment at the apex of PL. A large enough emission current was found at the relatively small macroscopic electric field of several V/µm, showing the efficient field enhancement at each graphene flake. The energy spectrum of the emitted electron from PL was slightly broader than that of metals, reflecting the characteristic DOS shape of the π-bands of graphene, and this result is also supported by the recursion-transfer-matrix (RTM) simulations of field emission. A large amount of chemically stable emission sites due to graphene at the apex of PL leads to a large and stable emission current, which was also stable even at high-pressure environments up to 10^- 4 Pa of N₂. Therefore, the graphitized PL can be utilized as a low-cost electron emitter with high performance. At the same time, it can also be used for specimens for fundamental investigations of graphene edges.