Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Cross-plane conductance through a graphene/molecular monolayer/Au sandwich
AU - Li, Bing
AU - Famili, Marjan
AU - Pensa, Evangelina
AU - Grace, Iain
AU - Long, Nicholas J.
AU - Lambert, C.
AU - Albrecht, Tim
AU - Cohen, Lesley F.
PY - 2018/11/14
Y1 - 2018/11/14
N2 - The functionalities offered by single-molecule electrical junctions are yet to be translated into monolayer or few-layer molecular films, where making effective and reproducible electrical contact is one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made with 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 graphene, yielding high-conductance devices. We elucidate the nature of the 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, demonstrates that between 10% and 100% of the molecules make contact with the electrodes, which is several orders of magnitude greater than that achieved to date in the literature. © 2018 The Royal Society of Chemistry.
AB - The functionalities offered by single-molecule electrical junctions are yet to be translated into monolayer or few-layer molecular films, where making effective and reproducible electrical contact is one of the challenging bottlenecks. Here we take a significant step in this direction by demonstrating that excellent electrical contact can be made with 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 graphene, yielding high-conductance devices. We elucidate the nature of the 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, demonstrates that between 10% and 100% of the molecules make contact with the electrodes, which is several orders of magnitude greater than that achieved to date in the literature. © 2018 The Royal Society of Chemistry.
KW - Current voltage characteristics
KW - Electric contacts
KW - Electrochemical electrodes
KW - Gold
KW - Graphite electrodes
KW - Molecules
KW - Monolayers
KW - Quantum chemistry
KW - Quantum electronics
KW - Electrical contacts
KW - Electrical junctions
KW - Graphene contacts
KW - Graphene electrodes
KW - HOMO-LUMO energies
KW - Junction properties
KW - Orders of magnitude
KW - Transmission probabilities
KW - Graphene
U2 - 10.1039/c8nr06763e
DO - 10.1039/c8nr06763e
M3 - Journal article
VL - 10
SP - 19791
EP - 19798
JO - Nanoscale
JF - Nanoscale
SN - 2040-3364
IS - 42
ER -