Effect of surface roughness on the self-assembly of octadecanethiol monolayer on to polycrystalline noble metal surfaces

Abstract

The role of surface roughness on defect formation in ocatadecanethiol monolayer covered surfaces of gold, silver and copper has been investigated using cyclic voltammetry and scanning tunneling microscopy. The adsorption of alkanethiol on surfaces subjected to various 'pre-treatments like mechanical polishing using different grades of emery and alumina indicates that a surface polished with 0.05 μm alumina has a significantly greater number of defect sites, thereby allowing access to redox species, compared to a surface treated with coarse emery. Scanning tunneling microscopic studies reveal that for a given area, a 'smooth' alumina polished surface has a number of closely spaced corrugations compared to a surface roughened using course emery. From these results, we establish that there exists a direct corielation between surface roughness and barrier efficiency.