Coherent Carrier Transport and Scattering by Lattice Defects in Single- and Multi-Branch Carbon Nanoribbons

We introduce a theoretical model for the investigation of the scattering properties by defects in semiconducting carbon nanoribbons. The analysis of multichannel coherent transport in the presence of discontinuities performed by means of a numerical solver, which was previously shown to correctly predict the electronic properties of carbon nanotubes, in some respects analogous to the nanoribbon. A scattering-matrix representation has been used to characterize the propagation and scattering of the periodic wave functions of carriers traveling along the carbon nanoribbon. Results show that reflection of charge is important for the defect types considered, i.e., atomic vacancy, potential deformation, and discontinuity caused by a 120° bifurcation. Reflection may be enhanced by interaction resonance between successive or periodic discontinuities. The dependence of scattering on carrier energy, referred to the band edge, has also been investigated: Generally, reflection decreases as carrier energy increases. The analysis suggests that the operation of devices employing carbon nanoribbons, such as nanotransistors, may be quite affected by the presence of lattice defects