Structure of Heptanethiolate Monolayers on Au(111): Adsorption from Solution vs Vapor Deposition

Abstract

A combined low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) study on the structural properties of heptanethiol (C7H15SH) monolayers prepared by either adsorption from the liquid or chemical vapor deposition (CVD) on Au(111) single crystal surfaces has been performed. Deposition from the vapor produces a commensurate c(17×√3) superstructure which exhibits a well-defined LEED pattern. XPS data recorded for these films reveal that the hydrocarbon molecules are orientated with their axes parallel to the substrate surface. Compared to the more commonly used fabrication of alkanethiolate self-assembled films by adsorption from solution the c(17×√3) CVD film exhibits a coverage of less than 40%.