| Summary: | 碩士 === 國立臺灣大學 === 化學研究所 === 98 === Ultramicroelectrodes (UMEs) are wildly used in trace sample analysis and some kinetic reaction studies because of their fast mass transfer and low charging current properties. However, the small effective size of UMEs also leads to a decrease in Faradaic signal and results in a low signal-to-noise ratio. Ultramicroelectrode arrays (UMEAs) were thus developed to solve the problem. In general, the silicon technology used to fabricate UMEAs involves photolithography and chemical etching for properly controlling their structure. However, the technology uses sophisticated instruments, which makes the fabrication process costly. Its solvent waste also raises environmental concerns. In this study, we introduced a novel and facile method to fabricate UMEAs on silicon wafers. It has the advantages of low fabrication cost and of posing no harm to the environment. The UMEs were electrochemically developed from a copper-based line structure which was produced by the annealing in oxygen environment of a copper thin films deposited on silica-covered silicon chip. The resulting UMEA structure (termed silica-isolated UMEA, SUMEA) was studied using scanning electron microscopy (SEM) and scanning Auger electron microscopy (SAM); the SUMEA electrochemical properties were determined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in both ferrocene (organic) or ruthenium hexamine (aqueous). The results showed that there were multiple UMEs on a single chip. The Faradaic signal was enhanced while the unique UME properties were preserved. The kinetic calculations from the CVs were also agreed with the UME properties in SUMEA. Further electrical properties of SUMEA were analyzed using EIS, in which an equivalent circuit was assumed to describe the electrical conduction in SUMEA. The relative electrical parameters of the SUMEA were obtained using the impedance fitting in Nyquist plot, and confirmed by the kinetic calculation of the steady-state cyclic voltammogram, which shows the assumed equivalent circuit is suitable to describe the electrical behavior of the SUMEA.
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