Probing the Electronic Properties of Materials that Self-Assemble

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Title: Probing the Electronic Properties of Materials that Self-Assemble
Author: Fuierer, Ryan R
Advisors: Dr. E.F. Bowden, Committee Member
Dr. D.L. Feldheim, Committee Co-Chair
Dr. C.B.Gorman, Committee Co-Chair
Dr. T.B. Gunnoe, Committee Member
Dr. Jan Genzer, Committee Member
Abstract: Developing methods to control the chemistry of surfaces on the 1—100 nm length scale is a fundamental and exciting challenge in many disciplines of science today because it opens new possibilities in fields ranging from molecular electronics (ME) to biomedicine to catalysis. Scanning probe microscopy techniques have been a key goal in achieving this challenge. This work begins with an exhaustive review of scanning probe lithography techniques using self-assembled monolayer (SAM) systems reported in the literature to date. Experimental study describes the development of a scanning probe lithography technique (termed replacement lithography) in which an STM tip selectively desorbs organothiolate SAMs in a predefined pattern, allowing a replacement thiol to adsorb onto the exposed gold in the patterned region. The replacement parameters were investigated using electroactive containing replacement thiol species because they displayed large apparent height contrasts in STM images, allowing the efficacy of the pattern to be easily ascertained. These data were subsequently employed to create mesoscale chemical gradients with replacement lithography. The electronic properties of redox active SAMs were also shown to display negative differential resistance in current-voltage measurements, a behavior that has possible utility in the development of ME devices. Temporal investigations monitoring the stochastic variation in apparent height contrasts in STM images of electroactive containing SAM guest species isolated within insulating host SAM matrices was also studied. The observations from these data may lend insight to how ME candidates might behave when sandwiched in a two-electrode configuration (metal-SAM-metal junction).
Date: 2004-05-21
Degree: PhD
Discipline: Chemistry
URI: http://www.lib.ncsu.edu/resolver/1840.16/4457


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