Talirz, LeopoldSode, HajoKawai, ShigekiRuffieux, PascalMeyer, ErnstFeng, XinliangMuellen, KlausFasel, RomanPignedoli, Carlo A.Passerone, Daniele2019-09-062019-09-062019-09-062019-08-2110.1002/cphc.201900313https://infoscience.epfl.ch/handle/20.500.14299/160915WOS:000482519600001We study the band gap of finite NA=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 8 nm and more is converged to within 50 meV of its bulk value of approximate to 2.3eV, while the band gap opens by several hundred meV in very short 7-AGNRs. We demonstrate that even an atomic defect, such as the addition of one hydrogen atom at the termini, has a significant effect - in this case, lowering the band gap. The effect can be captured in terms of a simple analytical model by introducing an effective "electronic length".Chemistry, PhysicalPhysics, Atomic, Molecular & ChemicalChemistryPhysicsmicroscopetext::journal::journal article::research article