  We address electron transport in honeycomb lattice ribbons with armchair
edges attached to two semi-infinite one-dimensional metallic electrodes within
the tight-binding framework. Here we present numerically the conductance-energy
and current-voltage characteristics as functions of the length and width of the
ribbons. Our theoretical results predict that for a ribbon with much smaller
length and width, so-called a nanoribbon, a gap in the conductance spectrum
appears across the energy E=0. While, this gap decreases gradually with the
increase of the size of the ribbon, and eventually it almost vanishes. This
reveals a transformation from the semiconducting to the conducting material,
and it becomes much more clearly visible from our presented current-voltage
characteristics.
