  Point sources exhibit low threshold electron emission due to local field
enhancement at the tip. The development and implementation of tip emitters have
been hampered by the need to position them sufficiently apart to achieve field
enhancement, limiting the number of emission sites and therefore the overall
current. Here we report low threshold field (< 0.1V/um) emission of multiple
electron beams from atomically thin edges of reduced graphene oxide (rGO).
Field emission microscopy (FEM) measurements show evidence for interference
from emission sites that are separated by a few nanometers, suggesting that the
emitted electron beams may be coherent. Based on our high-resolution
transmission electron microscopy, infrared spectroscopy and simulation results,
field emission from the rGO edge is attributed to a stable and unique
aggregation of oxygen groups in the form of cyclic edge ethers. Such closely
spaced electron beams from rGO offer prospects for novel applications and
understanding the physics of linear electron sources.
