Transport gaps in ideal zigzag-edge graphene nanoribbons with chemical edge disorder

Abstract

The effect of chemical edge disorder (CH and CH2) on the electron transport in ideal zigzag graphene nanoribbons (ZGNRs) is studied by using density functional theory (DFT) and the mean-field Hubbard model based quantum transport calculations. It is shown that a certain length of defective edge blocks can lead to a saturated suppression of the transmission through the lowest-energy bulk channel, where only two contiguous CH2 edge hybridizations at both edges is enough for ZGNRs narrower than ten zigzag chains. It suggests that the transport gap is established with the increasing heterogeneity of sp2 (CH edge) and sp3 (CH2 edge) hybridizations. With increasing the concentration (P) of sp3 over sp2 edge carbons, the transmission is shown to decrease exponentially by one order of magnitude until P ~ 0.3 with a saturated behavior around P = 0.5 and further decrease as P approaches 1. These findings show that the conductance can change more than 2 orders of magnitude with strong dependence on the edge chemistry even for structurally ideal ZGNRs.