Molecular self-assembly guided by surface reconstruction: CH₃SH monolayer on the Au(1 1 1) surface

Self-assembly of methanethiol (CH₃SH) on Au(1 1 1) was studied using scanning tunneling microscopy at T < 150 K when the S-H bond is intact. The CH₃SH monolayer assumes a commensurate structure with a fenced((6, 2; 0, 2)) unit-cell. Only one of three possible azimuthal domains of the monolayer was observed with domain walls pinned at the rotational boundaries of the herringbone reconstruction. From a real-time observation of monolayer formation at T = 60 K we propose a phenomenological model for the growth of preferential domains, which is based on the interplay between molecular detachment from domain boundaries and anisotropic mass transport on the Au(1 1 1) surface due to its herringbone reconstruction.