Graphene as a Promising Electrode for Low-Current Attenuation in Nonsymmetric Molecular Junctions

Qian Zhang (1, 2) , Li Liu (3) , Shuhui Tao (2, 1) , Congyi Wang (2) , Cezhou Zhao (4) , César González (5, 6) , Yannick J. Dappe (5) , Richard J. Nichols (1) , Li Yang (2, 1)

1 Department of Chemistry University of Liverpool
2 Department of Chemistry, Suzhou, Jiangsu, 215123 China
3 Department of Chemistry and Chemical Engineering, China
4 University of Liverpool
5 GMT - Groupe Modélisation et Théorie
6 UGR - Universidad de Granada = University of Granada

We have measured the single-molecule conductance of 1,$\it n$-alkanedithiol molecular bridges ($\it n$ = 4, 6, 8, 10, 12) on a graphene substrate using scanning tunneling microscopy (STM)-formed electrical junctions. The conductance values of this homologous series ranged from 2.3 nS ($\it n$= 12) to 53 nS ($\it n$= 4), with a decay constant β$_n$ of 0.40 per methylene (−CH$_2$) group. This result is explained by a combination of density functional theory (DFT) and Keldysh− Green function calculations. The obtained decay, which is much lower than the one obtained for symmetric gold junctions, is related to the weak coupling at the molecule−graphene interface and the electronic structure of graphene. As a consequence, we show that using graphene nonsymmetric junctions and appropriate anchoring groups may lead to a much-lower decay constant and more-conductive molecular junctions at longer lengths.

Mots clés: single molecule conductance; Graphene-based electrode; charge transport; alkanedithiol; density functional theory

Domaines: Physique [physics]

Qian Zhang, Li Liu, Shuhui Tao, Congyi Wang, Cezhou Zhao, et al.. Graphene as a Promising Electrode for Low-Current Attenuation in Nonsymmetric Molecular Junctions. Nano Letters, 2016, 16, pp.6534 - 6540. ⟨10.1021/acs.nanolett.6b03180⟩. ⟨cea-01490890⟩