Filled and empty states of alkanethiol monolayer on Au (1 1 1): Fermi level asymmetry and implications for electron transport

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Abstract

The electronic structure of the prototypical self-assembled monolayer (SAM) system, i.e. alkanethiol molecules on Au, is investigated via ultraviolet and inverse photoemission spectroscopy measurements. The determination of the density of filled and empty states of the system reveals that the metal Fermi level is significantly closer to the lowest unoccupied molecular orbital (LUMO) of the molecules than to their highest occupied molecular orbital (HOMO). The results suggest that charge carrier tunneling is controlled by the LUMO, rather than by the HOMO, in contrast to what is commonly assumed.

Highlights

Alkanethiol SAMs on Au are investigated via UPS and IPES measurements. ► The metal Fermi level is significantly closer to the LUMO than to their HOMO. ► The results suggest that charge carrier tunneling is controlled by the LUMO.

Section snippets

Acknowledgements

DC & AK gratefully acknowledge support from the US-Israel Binational Science Foundation. Work at Princeton was in part supported by the National Science Foundation (DMR-1005892) and the Princeton MRSEC of the National Science Foundation (DMR-0819860). Work at the Weizmann received also partial support from the Israel Science Foundation, via a Centre of excellence and its NAno-ERA+ program. OY thanks the Azrieli foundation for a fellowship. DC. Holds the Schaefer chair in Energy research.

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