THEORETICAL STUDY ON ADSORBATE-INDUCED SURFACE STRESS IN THE SELF-ASSEMBLY OF ALKANETHIOLS ON GOLD

By using established statistical thermodynamic theory of adsorbate-induced surface stress of adsorption monolayer on metal surface, the surface stress Delta g in the self-assembly of alkanethiols on Au(111) surface has been calculated. The quantitative relations of the surface stress Delta g with the length N of the alkyl chain of the molecule and with the coverage. of molecules on Au(111) have been theoretically studied, respectively. The calculated results agree with Berger et al.'s experiment. The qualitative discrepancy between the theory and experiment on the sign of the surface stress has been resolved. Among various components of the adsorbate-adsorbate interaction energies in the adlayer, the substrate-mediated interaction is significant for the adsorbate-induced surface stress, which shows that indirect contribution of the adsorption energy of alkanethiols through the substrate-mediated interaction is very important.