AVS 56th International Symposium & Exhibition
    Surface Science Thursday Sessions
       Session SS2-ThM

Paper SS2-ThM9
XPS and AFM Characterization of Two Component Self-Assembled Monolayers on Au(111)

Thursday, November 12, 2009, 10:40 am, Room N

Session: Electron Activated Molecular Interfaces
Presenter: M.H. Cheng, University of California, Irvine
Authors: M.H. Cheng, University of California, Irvine
T. McIntire, University of California, Irvine
R.L. Grimm, University of California, Irvine
J.C. Hemminger, University of California, Irvine
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Water uptake on organic films is of great importance in a number of fields. We have used two-component alkanethiol self-assembled monolayers (SAMs) to prepare surfaces with varied hydrophilic character. These surfaces have been used to study water uptake as a function of hydrophilic/ hydrophobic character. The chemical composition and morphology of the two two-component alkanethiol self-assembled monolayers on Au(111) were characterized by x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Gold films on glass were prepared by piranha cleaning and in vacuo argon ion sputtering yielding carbon- and oxygen-free surfaces. Solution-phase chemistry forms a two-component SAM comprised of the octanethiol and 6-mercaptohexanoic acid. These components were selected for comparison with previous research in our laboratory regarding the interaction and temperature-programmed desorption (TPD) of water from organic surfaces of tuned hydrophobic and hydrophilic character. The ratio of the O(1s) to the Au(4f) peak areas in the XPS quantify the relative fraction of the carboxylic acid-terminated thiol in the SAM. The XPS spectra indicate that the relative fraction of the two thiol components in the surface adsorbed SAM phase does not correspond to the relative solution-phase concentrations. By comparison with water thermal desorption experiments, we discuss the implications for the interaction of water with methyl-terminated and carboxylic acid-terminated organic surfaces and partially-oxidized organic aerosol.