Ordered nucleation of a self-assembled monolayer on Au(111) studied by scanning tunneling microscopy

Abstract

Scanning tunneling microscopy (STM) of a self-assembled monolayer (SAM) deposited on Au(111) reveals ordered nucleation of two-dimensional molecular islands at the initial growth stage. The nucleation islands, which are composed of several tens of molecules each, have a periodicity of 7.3 nm × 14 nm in average and locate at the herringbone turns of the Au(111)−22 × √3 surface reconstruction. From numerous STM studies, it is confirmed that such periodic nucleation comprises a large homogeneous domain over an area of atomically flat Au(111) terrace, even if the 22 × √3 surface reconstruction does not show periodic herringbone turns throughout on the bare surface of Au(111) before SAM deposition. Here we propose that the periodic herringbone structure is also induced by adsorption process of SAM molecules, while the periodic SAM islands grow at surface-lattice dislocations induced by the Au(111) herringbone reconstruction.