Self-Assembly of an Octanethiol Monolayer on a Gold-Stepped Surface

We investigate the influence of the native staircase nanostructure of a Au(lll) vicinal surface upon the self-assembly of alkylthiols. Through a comparison with standard alkylthiol SAMs deposited on Au(111) flat surfaces, we show that on the vicinal surface the octanethiol monolayer (OT SAM) reproduces the nanopatterned staircase structure, giving rise to a new kind of molecular layer self-ordered on the nanometer scale. The SAM's structure is determined by UHV STM and PM-IRRAS measurements and exhibits a specific behavior relative to the nanostructured substrate. The differences from the film grown on Au( 111) are attributed to the influence of step edges on the molecular packing, leading to a specific 2D crystallographic order through the step edges.