Electrical transport through atomic carbon chains: The role of contacts

Chains of carbon atoms in the sp1 hybridization are the one-dimensional analog of graphene. The first experimental studies of electrical transport in atomic carbon chains have shown a much lower conductivity than the quantum conductance limit. Here we explain, experimentally and by ab-initio transport modeling, the limited conductivity by studying the influence of carbon contacts in different hybridization states on the electrical properties of carbon chains. In-situ measurements in an electron microscope allow the synthesis and electrical characterization of carbon chains. Current-voltage curves of carbon chains, spanning between carbon contacts with sp2-or sp3-hybridized contact atoms, are measured and calculated. Contact atoms in the sp2-hybridization allow up to two orders of magnitude higher current than through sp3 contacts. Another important factor is the electron distribution in the chain which is determined by an even or odd number of atoms. On the other hand, it is shown that the overall length of the chain and strain have only minor influence on the conductivity. A current carrying capacity of up to 6.5 μA at an applied voltage of 1.5 V is measured.

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