title: Surface dipole layer potential induced ir absorption enhancement in n-alkanethiol SAMs on GaAs(001).
abstract: 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.
authors.affiliation: Department of Electrical and Computer Engineering, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada.
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Marshall
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Lopinski
authors.forename: Farid
authors.initials: F
authors.lastname: Bensebaa
authors.forename: Jan J
authors.initials: JJ
authors.lastname: Dubowski