  Thermoelectric properties of finite graphene nanoribbons (GNRs) coupled to
metallic electrodes are theoretically studied in the framework of tight-binding
model and Green's function approach. When the zigzag sides are coupled to the
electrodes, the electron transport through the localized edge states can occur
only if the channel length between electrodes is smaller than the decay length
of these localized zigzag edge states. When the armchair edges are coupled to
the electrodes, there is an interesting thermoelectric behavior associated with
the mid-gap states when the GNR is in the semiconducting phase. Here we show
that the thermoelectric behavior of zigzag edge states of GNRs with armchair
sides connected to electrodes is similar to that of two parallel quantum dots
with similar orbital degeneracy. Furthermore, it is demonstrated that the
electrical conductance and power factor given by the zigzag edge states are
quite robust against the defect scattering.
