Molecule-Based Negative Differential Resistance Across a Self-Assembled Monolayer: Its Dependence on Monolayer Coverage and Tunneling Gap

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Title: Molecule-Based Negative Differential Resistance Across a Self-Assembled Monolayer: Its Dependence on Monolayer Coverage and Tunneling Gap
Author: Robuck, Holly Elizabeth
Advisors: Dr. Edmond F. Bowden, Committee Member
Dr. Christopher B. Gorman, Committee Chair
Dr. Daniel L. Feldheim, Committee Member
Abstract: A scanning tunneling microscope (STM) was used to perform current-voltage (I-V) measurements over electroactive self-assembled monolayers (SAMs). It was hypothesized that the redox potential of an electroactive molecule influences the peak position of negative differential resistance (NDR). For this research, a ferrocene terminated alkanethiol, a ferrocenyl-ketone terminated alkanethiol, and a methyl viologen terminated alkanethiol were used, giving a range of redox potentials. Variability from the tip and the sample made the detection of any discernable differences impossible in the NDR peak position when the different SAMs were used. To address the variability, experiments were conducted where the order of the SAM was increased. The STM tip was also coated with 2,2,2-trifluoroethanethiol to make the tip surface more homogeneous. The results of the experiments discussed in this thesis suggest that the mechanism that leads to NDR is much more complicated than the resonant tunneling model suggests.
Date: 2004-09-02
Degree: MS
Discipline: Chemistry
URI: http://www.lib.ncsu.edu/resolver/1840.16/2616


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