  The electron field emission (FE) properties of reduced graphene oxide (rGO)
cathodes produced by three different reduction methods were assessed and
compared. In particular, chemical reduction techniques, using either NaOH or
KOH as reducing agents, were compared with thermal reduction (TR) methods. Xray
photoelectron spectroscopy (XPS) measurements revealed that different reduction
techniques led to different GO lattice parameters. Furthermore, the work
function measured with ultraviolet photoelectron spectroscopy (UPS) varied
among the samples giving rise to different electron emission characteristics.
In particular, the cathodes prepared by the TR method presented the best FE
performance, showing a turnon field of as low as ca. 1.8 V mm^-1 and a field
enhancement factor of ca. 1300, which was very close however to that shown by
the NaOH-reduced sheets. The worst FE properties were exhibited by the
KOH-reduced nanosheets. In light of the above results, the role of the
different reduction techniques as well as the final rGO lattice characteristics
with regards to the emission performance are evaluated and discussed.
