Band Gap of Atomically Precise Graphene Nanoribbons as a Function of Ribbon Length and Termination

Abstract

We study the band gap of finite $N_A=7$ armchair graphene nanoribbons (7-AGNRs) on Au(111) through scanning tunneling microscopy/spectroscopy combined with density functional theory calculations. The band gap of 7-AGNRs with lengths of 6 nm and more is converged to within 0.1 eV of its bulk value of 2.3 eV, while the band gap opens by several hundred meV in very short 7-AGNRs. The termination has a significant effect on the band gap, doubly hydrogenated termini yielding a lower band gap than singly hydrogenated ones.

Submitted version (preprint, pre-reviewing) to ChemPhysChem (An invited contribution to a Special issue on On-SurfaceSynthesis)