AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS1+AS+BI-FrM

Paper SS1+AS+BI-FrM4
Structure of Self-assembled Monolayers of Alkanethiols and Disulfides on Au(111)

Friday, October 29, 1999, 9:20 am, Room 606

Session: Organic Films/Self-Assembled Monolayers
Presenter: H. Nozoye, National Institute of Materials and Chemical Research, Japan
Authors: H. Nozoye, National Institute of Materials and Chemical Research, Japan
C. Kodama, University of Tsukuba, Japan
T. Hayashi, University of Tsukuba, Japan
Correspondent: Click to Email
Self-assembled monolayer (SAM) films of alkanethiols and alkyldisulfides have been attracting an increasing interest. However, we do not have a concrete picture of SAM, e.g. is the SH bond broken on the surface ? , is the SS bond formed on the surface ?, or where is the adsorption site of S ?. We studied these problems by means of STM, HREELS, high-sensitivity LEED, and TPD. Alkanethiols (C1-C10) and alkyldisulfides (C2-C12) were adsorbed on a Au(111) single crystal surface at room temperature or at around 120 K. Dersorption of H2, parent alkanethiol, alkylthiolate radical, and alkyldisulfide were observed in TPD and a vibration peak assigned to a SS bond was missing in HREEL spectra. We clearly concluded that the SH bond of alkylthiols breaks at low temperature forming alkylthiolates on the surface. Furthermore, the SS bond of alkyldisulfides was shown to be broken on the surface, forming alkylthiolate. The Au-S bond of alkylthiolates on the surface gave a relatively strong peak in HREEL spectra. We will discuss the formation process and the relation between the local structure and the long-range order of SAM.