Controlling local disorder in self-assembled monolayers by patterning the topography of their metallic supports

Micropatterning is a powerful method for controlling surface properties, with applications from cell biology to electronics1,2,3,4,5,6,7,8. Self-assembled monolayers (SAMs) of alkanethiolates on gold and silver9,10,11—the structures most widely used for preparing organic films with specific surface properties—are usually patterned by partitioning the surface into regions formed from different thiols12,13,14,15. Here we describe a way to pattern SAMs using a single alkanethiol on substrates consisting of regions of different topography: planar islands of one metal on the surface of a second (which may be different from or the same as the first). These topographically patterned SAMs consist of three regions: two planar surfaces and a transition region between the two. The characters of the SAMs on these three regions were inferred from images of three structures that form on them: condensation figures, patterns of crystals of CaCO3 and regions of selective etching. The transition region is more active in the processes generating these structures than either of the two planar regions, and we propose that this activity is due to the relatively high disorder in the organic film there. We believe that this ability to control the local disorder in a SAM with high resolution will be important in controlling processes such as nucleation, wetting, adhesion and etching on scales of below 50 nm to 5 µm.