title: Revealing the molecular structure of single-molecule junctions in different conductance states by fishing-mode tip-enhanced Raman spectroscopy.
abstract: The conductance of single-molecule junctions may be governed by the structure of the molecule in the gap or by the way it bonds with the leads, and the information contained in a Raman spectrum is ideal for examining both. Here we demonstrate that molecule-to-surface bonding may be characterized during electron transport by 'fishing-mode' tip-enhanced Raman spectroscopy (FM-TERS). This technique allows mutually verifiable single-molecule conductance and Raman signals with single-molecule contributions to be acquired simultaneously at room temperature. Density functional theory calculations reveal that the most significant spectral change seen for a gold-4,4'-bipyridine-gold junction results from the deformation of the pyridine ring in contact with the drain electrode at high voltage, and these calculations suggest that a stronger bonding interaction between the molecule and the drain may account for the nonlinear dependence of conductance on bias voltage. FM-TERS will lead to a better understanding of electron-transport processes in molecular junctions.
authors.affiliation: State Key Laboratory of Physical Chemistry of Solid Surfaces and Key Laboratory of Analytical Sciences, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Liu
authors.forename: Song-Yuan
authors.initials: SY
authors.lastname: Ding
authors.forename: Zhao-Bin
authors.initials: ZB
authors.lastname: Chen
authors.forename: Xiang
authors.initials: X
authors.lastname: Wang
authors.forename: Jing-Hua
authors.initials: JH
authors.lastname: Tian
authors.forename: Jason R
authors.initials: JR
authors.lastname: Anema
authors.forename: Xiao-Shun
authors.initials: XS
authors.lastname: Zhou
authors.forename: De-Yin
authors.initials: DY
authors.lastname: Wu
authors.forename: Bing-Wei
authors.initials: BW
authors.lastname: Mao
authors.forename: Xin
authors.initials: X
authors.lastname: Xu
authors.forename: Bin
authors.initials: B
authors.lastname: Ren
authors.forename: Zhong-Qun
authors.initials: ZQ
authors.lastname: Tian
mesh_terms: D004553:Electric Conductivity; D004566:Electrodes; D004574:Electromagnetic Fields; D055590:Electromagnetic Phenomena; D004579:Electron Transport; D006046:Gold / Q000737:chemistry; D016252:Microscopy, Scanning Tunneling; D015394:Molecular Structure; D050607:Organogold Compounds / Q000032:analysis* / Q000737:chemistry; D011725:Pyridines; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties
chemical_list: D050607:Organogold Compounds; D011725:Pyridines; D006046:Gold; C034306:4,4'-bipyridyl