Graphene nanoribbons with both armchair- and zigzag-shaped hydrogen-passivated edges (AGNR and ZGNR) have band gaps. Son et al. showed that the gap s value depends on the width of the ribbon and that the application of a uniform external electric field Eext across a ZGNR reduces the band gap. Moreover, for a critical Eext, the ZGNR becomes half-metallic. In the case of an 8-chain zigzag ribbon, the critical Eext is 2 V/nm within the local-density approximation (LDA). Motivated by tese findings, we study the influence on the gap of the electric field produced by a polar ad-molecule to the surface on an 8-zigzag ribbon. The formula units of the ad-molecules studies are NH3(CH)6CO2 and NH3(CH)10CO2. We show that the band gap is reduced from 0.52 eV without the ad-molecule to 0.28 eV with the ad-molecule within the generalized gradient approximation (GGA). Also, combining Eext of 1 V/nm and the ad-molecule induces the 8-chain ribbon to become half-metallic. These results suggest possible uses for the grapheme nanoribbons as sensors or switching devices.
Citation: Nano Letters
Pub Type: Journals