Inducing aromaticity patterns and tuning the electronic transport of zigzag graphene nanoribbons via edge design

Despite its remarkable electronic properties, graphene is a semimetal, or zero-band-gap semiconductor, which limits its potential applications in electronics. Cutting graphene into nanoribbons is one of the most successful approaches to opening the band gap of graphene toward applications. However, whereas armchair graphene nanoribbons exhibit semiconducting behavior, zigzag-edged structures are still semimetals. In this work, we perform periodic density functional theory (DFT) calculations on the electronic structure, together with nonequilibrium Green's function (NEGF) transport-property calculations, of different tailored-edge zigzag graphene nanoribbons. More precisely, we provide a complete description of the relation between band gap, transport properties, and aromaticity distribution along these materials, based on DFT results and Clar's sextet theory. The edge design is also shown to be applicable for finite fragments of carbon nanotubes in which the electronic confinement is similar. This ansatz provides different methods for the rational edge design of zigzag graphene nanoribbons, which induces aromaticity patterns and opens the band gap toward electronic applications. The mean bond length (MBL) geometric parameter and the six-center index (SCI) aromaticity descriptor are used to analyze the aromaticity patterns.