Abstract
We have measured the conductance of three pyridyl-terminated molecules binding to Ag electrodes by using electrochemical jump-to-contact scanning tunneling microscopy break junction approach (ECSTM-BJ). Three molecules, including 4,4′-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA), contacting with Ag electrodes show three sets of conductance values, which follow the order of BPY > BPY-EE > BPY-EA. These values are smaller than those of molecules with Au electrodes, but larger than those of molecules with Cu electrodes. The difference may attribute to the different electronic coupling efficiencies between the molecules and electrodes. Moreover, the influence of the electrochemical potential on the Fermi level of electrodes is also discussed.
Highlights
Single metal-molecule-metal junctions have attracted much attention for their fundamentally important role in molecular electronics [1,2,3]
We have developed an electrochemical jump-to-contact scanning tunneling microscopy break junction approach (ECSTM-BJ) [23]
Since the pyridyl group has received much attention [15,17,25,26,27], we recently extended this approach to the conductance measurement of pyridyl-based molecules binding to Cu electrode, which shows that the single-molecule conductance with pyridyl-Cu contacts is smaller than that with pyridyl-Au contacts [28]
Summary
Single metal-molecule-metal junctions have attracted much attention for their fundamentally important role in molecular electronics [1,2,3]. While the molecular structure is demonstrated to influence the charge transport through single-molecule conductance [4,5], the contact between electrode and molecule plays an important role [6,7]. We have developed an electrochemical jump-to-contact scanning tunneling microscopy break junction approach (ECSTM-BJ) [23]. By using this approach, single-molecule junctions with carboxylic acid binding to different metallic electrodes were systematically investigated [9,24]. We focus on the single-molecule junctions with pyridyl group (Figure 1a) binding to Ag contacts by ECSTM-BJ. Influence of the electrochemical potential on the Fermi level of electrode is discussed
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