Electron Transport Properties of Atomic Carbon Nanowires between Graphene Electrodes

Abstract

Long, stable, and free-standing linear atomic carbon wires (carbon chains) have been carved out from graphene recently [Meyer et al. Nature (London) 2008, 454, 319; Jin et al. Phys. Rev. Lett. 2009, 102, 205501]. They can be considered as extremely narrow graphene nanoribbons or extremely thin carbon nanotubes. It might even be possible to make use of high-strength and identical (without chirality) carbon wires as a transport channel or on-chip interconnects for field-effect transistors. Here we investigate electron transport properties of linear atomic carbon wire-graphene junctions by combining nonequilibrium Green's function with density functional theory. For short wires, linear ballistic transport is observed in wires consisting of odd numbers of carbon atoms but not in those consisting of even numbers of carbon atoms. For wires longer than 2.1 nm as fabricated above, however, the ballistic conductance of carbon wire-graphene junctions is independent of the structural distortion, structural imperfections, and hydrogen impurity adsorbed on the linear carbon wires, except for oxygen impurity adsorption under a low bias. As such, the epoxy groups might be the origin of experimentally observed low conductance in the carbon chain. Moreover, double-atomic carbon chains exhibit a negative differential resistance effect.

Progressive structural and electronic properties of nano-structured carbon atomic chains

“…The alternating distribution of bond length of short chains is in good agreement with other reported theoretical values. 14,16,17,19,31,32 The total electronic charge density distribution (Fig. 1) is consistent with the bond length distribution along the chain.…”

“…The dependence of the DOS at E F on the number of C atoms in the chain, presented in Figure 4, shows oscillatory behavior with the number of carbon atoms in the chain. As high DOS near E F leads to high conductance, 16,19 we can conclude that odd numbered chains should have higher conductivity and even-numbered chains should prove poor conductors. For a given N a AGNR-CAC-N a AGNR, the DOS at E F generally increases with the number of atoms in the odd-numbered CAC.…”

“…Due to the metallic character and good conductance, ZGNRs are chosen as the electrodes and the transport properties of chain-ZGNR junctions are extensively studied by several research groups. [16][17][18][19][20] However, AGNRs are not choosen as the electrodes because of their semiconducting or semimetallic nature, providing poor conductance. Theoretical results for transport along GNR-CAC-GNR have recently been presented.…”

“…Theoretical results for transport along GNR-CAC-GNR have recently been presented. Shen et al 19 suggest that for ZGNR-CAC-ZGNR with short CAC, ballistic transport should be observed for odd-numbered chains but not for even-numbered chains.…”

“…In this respect, the work by Lang and Avouris is noteworthy. [16][17][18] Using a similar technique, Shen et al 19 have investigated transport properties of ZGNR-ended CAC systems. Because of the metallic properties of ZGNRs, they prefer to use these as leads.…”