AVS 47th International Symposium
    Surface Science Friday Sessions
       Session SS+MC-FrM

Paper SS+MC-FrM6
Synchrotron-based XPS Study of 1-Decanethiol Chemisorbed on Au(111)

Friday, October 6, 2000, 10:00 am, Room 209

Session: Characterization of Oxides and Thin Films
Presenter: Y.W. Yang, Synchrotron Radiation Research Center, Taiwan
Authors: Y.W. Yang, Synchrotron Radiation Research Center, Taiwan
L.J. Fan, National Tsing Hua University, Taiwan
L.J. Lai, Synchrotron Radiation Research Center, Taiwan
Correspondent: Click to Email
Self-assembled monolayers have been the subject of intense research due to their potential applications in areas of lubrications, corrosion inhibitions, gas sensors, etc. We combined TDS and synchrotron-based, high resolution core level spectroscopy to study the chemisorption of 1-decanethiol monolayer on Au(111) surface with the molecular films prepared from both gas-phase dosing and solution immersion. On heating to temperatures higher than 400 K, decanethiolate starts to decompose, forming 1-decene via @beta@-hydrogen elimination, and leaves atomic sulfur on the surface. For thin films produced by both methods, S2p core level exhibits a single, well-characterized spin-orbit doublet with S2p@sub 2/3@ at 162.1 eV, indicating identical chemical interaction between sulfur and gold atoms in the films. However, C 1s core level starts from 284.0 eV at low coverage, develops a high-binding shoulder at intermediate coverage and eventually becomes a single peak at 285.0 eV for the high coverage prepared from solution phase. Angle-resolved XPS measurements of substrate core level signal provide a direct measure of the film thickness. The increases of C 1s binding energy is found to be associated with the incomplete final-state relaxation of the carbon atoms due to the thickness increase of the film as the carbon chains tilt toward the surface normal. Moreover, the implication of observing only a well-defined doublet of S 2p signal will be discussed in relation to the sulfur dimer model.