6312
Langmuir 2000, 16, 6312-6316
Chemically Well-Defined Lithography Using Self-Assembled Monolayers and Scanning Tunneling Microscopy in Nonpolar Organothiol Solutions Christopher B. Gorman,* Richard L. Carroll, Yufan He, Fang Tian, and Ryan Fuierer Department of Chemistry, North Carolina State University, Box 8204, Raleigh, North Carolina 27695-8204 Received March 3, 2000. In Final Form: May 9, 2000 A method of chemically well-defined, scanning tunneling microscope-based lithography 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 solution and an uncoated tip can be employed. Elevated relative humidity was important in the facility of this process, suggesting an electrochemical mechanism for replacement. The resolution of features written with this process is ca. 10-15 nm. In nonpolar solution, the apparent heights of self-assembled decanethiolate and dodecanethiolate monolayers are reversed compared to those observed in images obtained in air. When the thiol solution was exchanged after the first replacement, writing with two different thiols was demonstrated.
Introduction Recently there has been substantial interest in generating chemically well-defined patterns. Substantial progress has been made using various procedures to pattern thiol molecules on gold.1 Among them, various scanning probe lithography techniques have been reported where self-assembled monolayers (SAMs) are manipulated on small (e.g.,
