Nanofabrication of self-assembled monolayers: Advanced methodologies and applications.

摘要

We developed advanced scanning probe lithography (ASPL) methodologies for the nanometer-scale fabrication of thiol self-assembled monolayers (SAMs). First, we studied the stability of SAMs in the conditions under which they are fabricated.; Second, we developed a new multimode scanning probe microscope capable of automated scanning probe lithography. Complex nanostructures, including large arrays and nanodevice-like patterns, were fabricated.; Third, we systematically studied the influence of two fabrication parameters (the force applied by the tip and its speed during fabrication) on the resolution during AFM-based nanofabrication. Patterning imperfections induced by the piezoelectric scanner, the AFM cantilever and the feedback electronics were also described, and possible remedies suggested.; Fourth, we investigated the formation of a partial thiol-containing bilayer on top of SAMs in contact with highly concentrated thiol solutions. The following formation mechanism was proposed: (i) the matrix SAM rapidly exchanged with thiols in solution; (ii) protruding alkyl chains anchored a physisorbed thiol-containing monolayer on top of the SAM; (iii) hydrophobic forces drove the formation of a (partial) reverse bilayer film. Partial bilayer formation is not observed on nanopatterns fabricated in the SAM matrix. Thus, it might serve as a nanopattern transfer method. The bilayer deposition selectivity is attributed to differences in surface order between the pattern area and the surrounding exchanged SAM.