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Effect of Asymmetric Anchoring Groups on Electronic Transport in Hybrid Metal/Molecule/Graphene Single Molecule Junctions
Author(s) -
He Chunhui,
Zhang Qian,
Fan Yinqi,
Zhao Cezhou,
Zhao Chun,
Ye Jingyao,
Dappe Yannick J.,
Nichols Richard J.,
Yang Li
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201900424
Subject(s) - graphene , conductance , electrode , density functional theory , molecule , break junction , quantum tunnelling , materials science , scanning tunneling microscope , chemistry , molecular physics , condensed matter physics , nanotechnology , chemical physics , computational chemistry , optoelectronics , physics , organic chemistry
Abstract A combined experimental and theoretical study on molecular junctions with asymmetry in both the electrode type and in the anchoring group type is presented. A scanning tunnelling microscope is used to create the “asymmetric” Au‐S‐(CH 2 )n‐COOH‐graphene molecular junctions and determine their conductance. The measurements are combined with electron transport calculations based on density functional theory (DFT) to analyze the electrical conductance and its length attenuation factor from a series of junctions of different molecular length ( n ). These results show an unexpected trend with a rather high conductance and a smaller attenuation factor for the Au‐S‐(CH 2 ) n ‐COOH‐graphene configuration compared to the equivalent junction with the “symmetrical” COOH contacting using the HOOC‐(CH 2 ) n ‐COOH series. Owing to the effect of the graphene electrode, the attenuation factor is also smaller than the one obtained for Au/Au electrodes. These results are interpreted through the relative molecule/electrode couplings and molecular level alignments as determined with DFT calculations. In an asymmetric junction, the electrical current flows through the less resistive conductance channel, similarly to what is observed in the macroscopic regime.