Microcavities containing individually addressable recessed microdisk and tubular nanoband electrodes

by Henry, Charles Sherman; Fritsch, Ingrid

Construction and characterization of a new microcavity electrode system, microfabricated into alternating layers of gold and polyimide, is reported. The cavities contain individually addressable recessed microdisk (RMD) and tubular nanoband (TNB) gold electrodes inside a small cavity with a third electrode accessible at its rim. The cavity is cylindrical, with a 53 mu m diam and 8 mu m depth. The electrodes were characterized with cyclic voltammetry in Ru(NH3)(6)(3+)/KNO3 solution, and the experimental current was compared to that predicted from models. At slow scan rates (0.1 V s(-1)), the measured current for the TNB is within error of the current predicted from hemicylindrical diffusion models. The measured current for the RMD, which is about 300 times larger in area than the TNB, is within error of the model for hemispherical diffusion to planar microdisks. A similar current obtained for the RMD and TNB is consistent with the dominance of diffusion to the edges at these time scales. At faster scan rates (204 V s(-1)), the current for the TNB is significantly higher than predicted. At 204 V s(-1) at the RMDs, the current is less than expected for the model for linear diffusion. This is probably partly due to uncompensated resistance and the manner in which charging current was subtracted from the total current. The quality of construction of the system was evaluated by determining the dependence of area-normalized capacitance on scan rate for both the RMD and TNB and comparing it to that for a macroelectrode. The data are consistent with good adhesion between the electrodes and polyimide insulator. (C) 1999 The Electrochemical Society. S0013-465(98)10-069-1. All rights reserved.

Journal of the Electrochemical Society
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1945-7111; 0013-4651