Master of Science in Chemical Engineering (MSChE)


Chemical Engineering

Document Type



Electrodeposited AuCo and Au/Co multilayers are of interest as potential materials for MEMS components. AuCo alloys have been fabricated by the electrodeposition technique, but from cyanide-containing electrolyte. In this study, we explored the electrodeposition of AuCo and Au/Co multilayer thin films, and nanowires, from a non-cyanide electrolyte. Two variables were considered: the concentration of citric acid and pH. The changes in composition were described by the differences in the partial current densities. The effect of pH and citric acid concentration on the deposit composition and current efficiency was investigated. Results showed that a lower citric acid concentration was favored for multilayered Au/Co deposits with disparate compositions in each layer. At low current density elemental gold is deposited, while at high current density a cobalt rich alloy (98.7 % Co) is obtained. An increase in the citric acid concentration requires larger applied current density to achieve the same cobalt concentration. The influence of pH has a similar behavior. The lower the pH, the larger is the disparity between the compositions. The current efficiency drops with increasing citric acid concentration and pH. By comparing the partial current densities, both the side reaction and Co rates are influenced by the citric acid and pH. Giant magnetoresistance (GMR) property was explored for Au/Co nanometric multilayers, and a large GMR (> -13 %) was found when the films were deposited on (100) Cu. The GMR changes from a positive to negative value depending on the Au and Co layer thicknesses. The application of the multilayered deposit to fabricate a nanomold was explored. The mold was fabricated by depositing the multilayer and selectively etching one layer. Electrodeposition of Au/Co multilayer nanowires was also fabricated in this study. Both alumina oxide and polycarbonate membranes were used as templates. A nanowire of 15 nm for Co and 25 nm for Au, which is closed to the calculated layer size, was confirmed by TEM analysis.



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Committee Chair

Elizabeth J. Podlaha