Sensing Molecular Adsorption Through Interfacial Electron Scattering in Atom -Scale Junctions
Castle, Patrick James
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https://hdl.handle.net/2142/84182
Description
Title
Sensing Molecular Adsorption Through Interfacial Electron Scattering in Atom -Scale Junctions
Author(s)
Castle, Patrick James
Issue Date
2005
Doctoral Committee Chair(s)
Bohn, Paul W.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Language
eng
Abstract
The goal of this work was to fabricate Au atom-scale junctions as the basis for robust, regenerable, nanostructured sensors to use with mass-limited samples for improved protection of health and safety. Atom-scale junctions were formed between two Au thin film electrodes. The inter-electrode gap was lithographically defined, and a microfluidic channel was aligned over the inter-electrode gap. The inter-electrode gap was reduced with electrodeposition, which was terminated at an atom-scale junction by setting a comparator to trigger a relay at a current corresponding to a junction conductance comparable to the conductance quantum. Based on conductance measurements and estimates from SEM images, atom-scale junctions were successfully formed. Lewis bases were introduced to atom-scale junctions, and the resulting alternating current impedance change was measured. For example, the interfacial scattering from chemisorption of 10 mM hexadecanethiol (HDT) on a 2.6 G0 atom-scale junction caused a normalized impedance change of 71% +/- 1%, with a noise level consistent with a population fluctuation of only 1 HDT molecule. To regenerate the device in situ, the junction was broken with a potential sweep and reformed with comparator-terminated electrodeposition. The atom-scale junction capability to measure small numbers of adsorption/desorption events makes a powerful case for pushing the limits of sensitivity for electrical measurements of single molecule events.
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