Ab initio study of gold-doped zigzag graphene nanoribbons

Abstract

The electronic transport properties of zigzag graphene nanoribbons (ZGNRs) through covalent functionalization of gold (Au) atoms is investigated by using non-equilibrium Green's function combined with density functional theory. It is revealed that the electronic properties of Au-doped ZGNRs vary significantly due to spin and its non-inclusion. We find that the DOS profiles of Auadsorbed ZGNR due to spin reveal very less number of states available for conduction, whereas non-inclusion of spin results in higher DOS across the Fermi level. Edge Au-doped ribbons exhibit stable structure and are energetically more favorable than the center Au-doped ZGNRs. Though the chemical interaction at the ZGNR-Au interface modifies the Fermi level, Au-adsorbed ZGNR reveals semimetallic properties. A prominent qualitative change of the I-V curve from linear to nonlinear is observed as the Au atom shifts from center toward the edges of the ribbon. Number of peaks present near the Fermi level ensures conductance channels available for charge transport in case of Au-center-substituted ZGNR. We predict semimetallic nature of the Au-adsorbed ZGNR with a high DOS peak distributed over a narrow energy region at the Fermi level and fewer conductance channels. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. The outcomes are compared with the experimental and theoretical results available for other materials.