Cross-plane Conductance through a Graphene/Molecular Monolayer/Au Sandwich

Research output: Contribution to journalArticle


  • Bing Li
  • Marjan Famili
  • Evangelina Pensa
  • Iain Mark Grace
  • Nicholas J. Long
  • Colin Lambert
  • Lesley Cohen

Colleges, School and Institutes


The functionalities offered by single-molecule electrical junctions have yet to be translated into monolayer or few-layer molecular films, where effective and reproducible electrical contact represents one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made to a monolayer biphenyl-4, 4’-dithiol (BPDT) molecular film, sandwiched between gold and graphene electrodes. This sandwich device structure is advantageous, because the current flows through the molecules to the gold substrate in a ‘cross-plane’ manner, perpendicular to the plane of the graphene, yielding high-conductance devices. We elucidate the nature of cross-plane graphene/molecule/Au transport using quantum transport calculations and introduce a simple analytical model, which captures generic features of the current-voltage characteristic. Asymmetry in junction properties results from the disparity in electrode electrical properties, the alignment of the BPDT HOMO-LUMO energy levels and the specific characteristics of the graphene electrode. The experimental observation of scalability of junction properties within the junction area, in combination with a theoretical description of the transmission probability of the thiol-graphene contact, demonstrate that between 10%-100% of the molecules are contacted to the electrodes, which is several orders of magnitude greater than achieved to date in the literature.


Original languageEnglish
Early online date27 Sep 2018
Publication statusE-pub ahead of print - 27 Sep 2018