Mechanical and charge transport properties of alkanethiol self-assembled monolayers on a au(111) surface: the role of molecular tilt

Yabing Qi; Imma Ratera; Jeong Y Park; Paul D Ashby; Su Ying Quek; J B Neaton; Miquel Salmeron

doi:10.1021/la703147q

Mechanical and charge transport properties of alkanethiol self-assembled monolayers on a au(111) surface: the role of molecular tilt

Langmuir. 2008 Mar 4;24(5):2219-23. doi: 10.1021/la703147q. Epub 2008 Jan 29.

Authors

Yabing Qi¹, Imma Ratera, Jeong Y Park, Paul D Ashby, Su Ying Quek, J B Neaton, Miquel Salmeron

Affiliation

¹ Materials Sciences Division, University of California Berkeley, Berkeley California 94720, USA.

PMID: 18225934
DOI: 10.1021/la703147q

Abstract

The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAMs) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant beta = 0.57 +/- 0.03 A-1 was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of approximately 1 A-1 found when the separation is varied by changing the length of the alkanethiol molecules. Calculations indicate that, for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.