Adsorption structures of alkanethiols self-assembled monolayers on the Cu(100) surface studied by S-K EXAFS and C-K NEXAFS spectroscopies

Abstract

We performed S-K XAFS and C-K NEXAFS experiments for alkanethiols (CH3(CH2)n-1SH; n=6,12,16) on Cu(100), and clarified the local structures around the S head groups and the orientation of alkyl chains; the S atoms were found to locate at a fourfold hollow site without surface reconstruction. These results are in clear contrast with the case of Cu(111), where the S atoms locate at a deep three-fold hollow site with significant lateral outward movements of the nearest neighbor Cu atoms. Such a structure difference might come from the different densities of the Cu atoms on these surfaces.