Uncovering the hidden gold atoms in a self-assembled monolayer of alkanethiol molecules on Au(111)

Abstract

Self-assembled monolayers (SAMs) of alkanethiols on Au(111) contain adatoms of gold in the form of gold thiolate (Au-S-R). Using localized water dissociation underneath the tip of a scanning tunneling microscope, we are able to break the Au-S bond within a confined area of an octanethiol SAM to release the gold adatoms which subsequently coalesce into single atomic layer gold islands. By measuring the volume of the resultant gold islands, and considering the incorporation of gold atoms into the herringbone reconstructed surface, we found about 0.22 ML of gold atoms are released during the desorption of the octanethiol SAM.