Interpolymer Self-Assembly of Bottom-up Graphene Nanoribbons Fabricated from Fluorinated Precursors

Interpolymer self-assembly of bottom-up graphene nanoribbons (GNRs) has been realized by using fluorinated anthracene trimer precursors (HFH-DBTA) deposited onto heated Au(111) substrate. Whereas polymers derived from conventional precursor [10,10'-dibromo-9,9'-bianthryl (DBBA)] are adsorbed on Au(111) without apparent close packing, poly-HFH polymers derived from HFH-DBTA are densely self-assembled and require a long annealing time for cyclo-dehydrogenation because of the steric hindrance. First-principles calculations based on density functional theory revealed that the partially fluorinated edges of HFH-DBTA make molecular substrate interaction weaker than that of DBBA, accelerate desorption, and leave islands of accumulated and locally aligned polymers. The partially fluorinated precursors also induce templating effects in interpolymer stacking because of H-F hydrogen bonding and F-F repulsion. The statistical analysis revealed that 84% of GNRs is parallel to the adjacent GNRs in the case of HFH-DBTA precursors. Field-effect transistors (FETs) were fabricated using such locally aligned multiple GNRs as channels. It has been found that on average, the on-current of the FETs is three times larger than that of FETs using less-aligned GNR channels made from the conventional DBBA precursors.