Sub-Nanometer Width Armchair Graphene Nanoribbon Energy Gap Atlas

Extended all-sp2-carbon
macromolecules have the potential
to replace silicon in integrated nanometer-scale devices. Up to now,
studies on the electronic properties of such structures, for example,
graphene nanoribbons, have been focused mostly on the infinitely long
limit, which is inadequate when approaching future devices with sub-10
nm control. Moreover, their electronic variation has not been systematically
assessed as a function of chemically diverse edge termini. Such knowledge
is central when prototyping potential all-carbon circuits. Here, we
present a graphene nanoribbon energy gap atlas based on density functional
tight-binding spin-polarized calculations of nearly ten thousand randomly
generated nanoribbons with a maximal nominal width of 1 nm and an
armchair long edge. We classify ribbon families and show that their
energy levels are strongly dependant on their termini edge states.
We notably reveal modulation of the bulk energy gap by 0.3 eV through
minimal edge modifications and put forward simple rules for inducing
antiferromagnetic edge states.