Self-Assembled Monolayers Exposed to Metastable Argon Beams Undergo Thiol Exchange Reactions

Self-assembled monolayers (SAMs) formed from alkanethiols on thin films of gold were exposed to a beam of metastable argon atoms through a stencil mask. The changes in the organizational structure of the alkyl chains in the SAM that resulted from exposure were characterized using reflection−absorption infrared spectroscopy. All spectroscopic evidence suggested that the SAMs become disordered after exposure to metastable argon atoms and that no apparent oxidation of the alkane chain occurred. The alkanethiolates in the regions of a SAM of dodecanethiolate damaged by the atom beam exchanged readily upon immersion in a solution of 16-mercaptohexadecanoic acid. The exchange reaction was selective for the regions of the SAM exposed to metastable argon atoms with patterns containing critical dimensions of <50 nm. A thin (<5 nm) polymeric multilayer was covalently linked to the carboxylic acid groups in the exposed regions of the SAM. The polymeric layer served as an improved resist against a commercial KI/I2-based etchant used to transfer the pattern into the thin film of gold.