期刊
NANO LETTERS
卷 14, 期 2, 页码 794-798出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl404143v
关键词
Level alignment; electronic coupling; single-molecule junctions; conductance switching; thermopower
类别
资金
- NSF MIRT program [DMR-1122594]
- Division of Materials Sciences and Engineering (Theory FWP) under Office of Basic Energy Sciences of the U.S. Department of Energy [DE-AC02-05CH11231]
We measure conductance and thermopower of single Au-4,4'-bipyridine-Au junctions in distinct low and high conductance binding geometries accessed by modulating the electrode separation. We use these data to determine the electronic energy level alignment and coupling strength for these junctions, which are known to conduct through the lowest unoccupied molecular orbital (LUMO). Contrary to intuition, we find that, in the high-conductance junction, the LUMO resonance energy is further away from the Au Fermi energy than in the low-conductance junction. However, the LUMO of the high-conducting junction is better coupled to the electrode. These results are in good quantitative agreement with self-energy corrected zero-bias density functional theory calculations. Our calculations show further that measurements of conductance and thermopower in amine-terminated oligophenyl-Au junctions, where conduction occurs through the highest occupied molecular orbitals, cannot be used to extract electronic parameters as their transmission functions do not follow a simple Lorentzian form.
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