AVS 49th International Symposium
    Organic Films and Devices Wednesday Sessions
       Session OF+EL-WeP

Paper OF+EL-WeP3
Photoemission Study of Dodecanthiol on Au (111)

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Organic Films and Devices
Presenter: J.M. Burst, University of New Orleans
Authors: H. Geisler, Xavier University of Louisiana
S. Sales, Xavier University of Louisiana
J.M. Burst, University of New Orleans
S.N. Thornburg, University of New Orleans
C.A. Ventrice Jr., University of New Orleans
Y. Losovyj, Louisiana State University
P.T. Sprunger, Louisiana State University
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The adsorption of alkanethiols on various single-crystal metal surfaces results in the formation of self-assembled monolayers (SAMs). Typically, SAMs are grown on surfaces that are immersed in aqueous solutions, and adsorption times of 15 hours or more are necessary to obtain well-ordered, defect free structures. In this study, 1-dodecanethiol was vapor deposited on Au (111) in ultra high vacuum, which produces a SAM in a period of only a few minutes. Angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) was used to determine the orientation and the electronic structure of the thiol. Deposition at room temperature gave no signature of thiol adsorption at the surface with either ARUPS or low energy electron diffraction (LEED). Deposition at ~100 K resulted in an ordered monolayer, as indicated by the dispersion of the thiol valence band emissions. A comparison between clean gold and the SAM spectra indicate that the 1-dodecanethiol adsorbs upright at a 20° angle to the surface normal. Deposition of multilayers of thiol at ~100 K produced a disordered overlayer with no dispersion of the valence band emissions. The onset of emission from the thiol valence band for the multilayer films was measured to be 3.5 eV below the Fermi level.