Fabrication and characterization of au disk mircoelectrodes

Au fiber disk microelectrodes with well defined geometries were fabricated by low temperature plasma enhanced chemical vapor deposition (PECVD). Silicon nitride thin films with thickness of 0.7 μm were deposited concentrically on the cylindrical length of 25 μm Au fibers. To form microelectrodes devices, the coated gold microfibre was connected to a copper leader with Ag epoxy. The thin film deposition was performed in a PECVD instrument with substrate temperature (340±10)°C. Comparing with chemical vapor deposition and resistive heating (CVD-RH), the insulation by the PECVD can be performed to metal microfibres with the low melting or softening points for the fabrication of microelectrodes as it offers the possibility to fabricate a surface coating at low temperature (≤450°C). The quality, thickness and adhesion to the fiber substrates of films were characterized by scanning electron microscopy. The films are found to be free of microcracks and have a quality seal with Au fibers. Cyclic voltammograms were obtained in electrolyte of 0.5 mmol/L K₃Fe₃(CN)₆ in 0.5 mol/L KCl solution. The electrochemical responses are sigmoidal in shape and indicate that the radial diffusion is the primary mode of mass transport at different scan rates. As a result, the silicon nitride coated disk microelectrodes exhibit an excellent microelectrode electrochemical response without using an epoxy sealant.