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

Research output: Contribution to journalArticle

Authors

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

Colleges, School and Institutes

Abstract

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.

Details

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