New tool for studying the in situ growth processes for self-assembled monolayers under ambient conditions

A new tool for studying self-assembled monolayer (SAM) nucleation and growth processes on faceted inorganic substrates under ambient conditions is reported herein. The methodology involves coating an atomic force microscope tip with molecules of interest and raster scanning across a substrate of interest with the modified tip. Large scale images of the deposition process provide kinetic information about the nucleation and growth of SAMs. The water meniscus, which is the transport medium in these experiments, is proposed to strongly influence the growth process for 1-octadecanethiol and 16-mercaptohexadecanoic acid. The former involves an island formation and subsequent growth behavior while the latter shows evidence of more random growth. Lattice-resolved images of both SAM structures have been obtained at the end of film growth, and in the case of the 1-octadecanethiol SAM, lattice-resolved images were obtained for the SAM islands. The virtues of this novel technique are its simplicity, adsorbate generality, and serial nature, which allows one to control monolayer growth in a step-by-step process with concomitant imaging capabilities.