Characterization of Au ring microelectrode with cyclic voltammetry and AC impedance spectroscopy

In this paper Au ring microelectrodes are fabricated and characterized. With an optical fibre core as a substrate Au film with thickness 300nm was coated by an electron beam evaporation system, then on this Au coated substrate a parylene passivation layer was deposited, forming the desired Au ring microelectrode. Scanning electron microscopy (SEM) was used to characterize the quality of the deposited films and the adhesion at the interfaces. With a CHI660D electrochemical workstation the electrochemical characterizations were performed at room temperature in a conventional three-electrode system. Cyclic voltammograms as a function of scan rate were sigmoidal form, a typical electrochemical response of microelectrodes. AC impedance frequency spectrum of the fabricated Au ring microelectrode was also obtained in a reversible system, and good agreement was found with the Randels-type equivalent circuit.