From graphene to graphite: A general tight-binding approach for nanoribbon carrier transport

In an effort to better understand the behavior of graphene, we developed an ab initio parametrized fit of hydrocarbon interactions, out to arbitrary neighbors, including forces. Our computed bands show that ribbons of graphene have increased numbers of zigzag edge states, and decreased armchair band gaps, when multilayered. Armchair ribbons are known to obey three families of gap-to-width relationships; we further find that carrier group velocity v(F) varies by family: small gaps have ideal v(F), and large gaps have +/- 20% deviations from ideal v(F). Boltzmann carrier transport simulations from calculated phonon scattering show a similar, familial conductance behavior, with peak field-effect mobility and saturated, small-field conductance increasing linearly with ribbon width.