Nanografting of Thiols with SAMs

The nanografting was performed on the (111) surface of a gold crystal onto which a SAM of decanethiol had been adsorbed. Imaging and lithography were done in contact mode in an aqueous solution containing octadecanethiol whose tail is eight carbon atoms longer than decanethiol. At low forces, the AFM simply imaged the SAM. However, when higher forces were applied during lithography, the AFM displaced the original SAM molecules. The longer-tailed molecules then diffused in to heal the SAM resulting in a raised surface from the protruding SAM tails. The spirals are 620 nm in diameter, with average line spacings of 40 nm, average line-widths (FWHM) of 15 nm, and average heights of 0.15 nm, and mono-atomic steps in the background. Imaged with the MFP-3D AFM. Courtesy of G. Liu, UC Davis.