Lithography Using an Atomic Force Microscope and Ionic Self-assembled Multilayers

Abstract

This thesis presents work done investigating methods for constructing patterns on the nanometer scale. Various methods of nanolithography using atomic force microscopes (AFMs) are investigated. The use of AFMs beyond their imaging capabilities is demonstrated in various experiments involving nanografting and surface electrochemical modification. The use of an AFM to manipulate a monolayer of thiols deposited on a gold substrate via nanografting is shown in our work to enable chemical modification of the surface of the substrate by varying the composition of the monolayer deposited on it. This leads to the selective deposition of various polymers on the patterned areas. Conditions for enhancing the selective deposition of the self-assembled polymers are studied. Such conditions include the types of polymers used and the pH of the polyelectrolyte solutions used for polymer deposition. Another method of nanolithography is investigated which involves the electrochemical modification of a monolayer of silanes deposited on a silicon substrate. By applying a potential difference and maintaining the humidity of the ambient environment at a certain level we manage to change the chemical properties of select areas of the silane monolayer and thus manage to establish selective deposition of polymers and gold nanoparticles on the patterned areas. Parameters involved in the patterning process using surface electrochemical modification, such as humidity levels, are investigated. The techniques established are then used to construct circuit elements such as wires.