  The impact of the edges and presence of dopants to the work function (WF) of
graphene nanoribbons (GNR) and nanoflakes was studied by an ab initio approach.
The strong dependence of the WF upon the GNR structure was found and a
promising character for the field emission by the donor type impurities was
observed. Basing on the predominant impact of the nanostructure edges to the
emission properties, the small graphene flakes were investigated as a possible
source for the electron emission. The obtained weak dependence of the low WF
values of the graphene flakes on their size and shape allows to suggest that
the pure carbon medium with high and uniform emission properties can be
fabricated by today technology.
