Chemically well-defined lithography using self-assembled monolayers and scanning tunneling microscopy in nonpolar organothiol solutions

A method of chemically well-defined, scanning tunneling microscope-based li thography is presented in which one thiolate in a self-assembled monolayer is removed and replaced with a second thiol. This method is distinguishable from other lithographic replacement processes on SAMs in that a nonpolar s olution and an uncoated tip can be employed. Elevated relative humidity was important in the facility of this process, suggesting an electrochemical m echanism for replacement. The resolution of features written with this proc ess is ca. 10-15 nm. In nonpolar solution, the apparent heights of self-ass embled decanethiolate and dodecanethiolate monolayers are reversed compared to those observed in images obtained in air. When the thiol solution was e xchanged after the first replacement, writing with two different thiols was demonstrated.