20 August 2009 Energy-level alignment of aryl thiols chemisorbed on metal surfaces: implications for charge transport
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Abstract
Photoemission spectra of self-assembled monolayers of para-phenylene-ethynylene thiols chemisorbed on gold have been measured. Three compounds were studied: 4,4'-bis(phenylethynyl)benzenethiol, 4-(phenylethynyl)benzenethiol, and benzenethiol. The monolayer spectra were interpreted with the aid of gas-phase photoemission spectra of 4,4'- bis(phenylethynyl)benzenethiol and benzenethiol. The work function of the monolayer-covered surface and alignment of the highest occupied π-state of the monolayer relative to the Fermi level of the substrate were determined from the monolayer spectra. The work function of the monolayer-covered surface decreased relative to that of the bare substrate by about an electronvolt. The shift is attributed to changes in the charge distribution at the interface associated with chemisorption. No statistically significant trend in the work function shift was observed with respect to oligomer length. This observation points to a near-constant interface dipole and the role of the gold-sulfur bond in determining energy-level alignment.
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Christopher D. Zangmeister, Steven W. Robey, Roger D. van Zee, Nadine E. Gruhn, Yuxing Yao, James M. Tour, "Energy-level alignment of aryl thiols chemisorbed on metal surfaces: implications for charge transport", Proc. SPIE 7396, Physical Chemistry of Interfaces and Nanomaterials VIII, 73960C (20 August 2009); doi: 10.1117/12.825276; https://doi.org/10.1117/12.825276
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