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Langmuir. 2009 Dec 1;25(23):13561-8. doi: 10.1021/la901888q.

Surface dipole layer potential induced ir absorption enhancement in n-alkanethiol SAMs on GaAs(001).

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  • 1Department of Electrical and Computer Engineering, UniversitĂ© de Sherbrooke, Sherbrooke, QuĂ©bec J1K 2R1, Canada.


The work function of n-alkanethiol self-assembled monolayers (SAMs) prepared on the GaAs(001) surface was measured using the Kelvin probe technique yielding the SAM 2D dipole layer potential (DLP). Direct n-dependent proportionality between the DLP values and the C-H stretching mode infrared (IR) absorption intensities was observed, which supports a correspondence of reported IR enhancements with the electrostatic properties of the interface. X-ray photoelectron spectroscopy is also used to verify the work function measurements. In addition, the principal components of the refractive index tensor are shown to be n-invariant in the ordered SAM phase. Our results suggest that a local field correction to the transition dipole moment accounts for the observed increase in IR activity through an increase to the electronic polarizability.

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