Submicron electrode gaps fabricated by gold electrodeposition at interdigitated electrodes

Electrodes with submicron gaps are desired for achieving high amplification redox cycling sensors. In this contribution we report the use of electrodeposition of gold in order to decrease the inter-electrode spacing at interdigitated electrodes. Using this method submicron spacings can be obtained without expensive techniques such as e-beam lithography or focused ion beam milling. Initially, gold interdigitated electrodes with a finger spacing of 2.5 μm were realized by lift-off processing. Using a commercial gold sulphite bath (ECF64D) and 100 ms current pulses of -1.78 μA, these gold electrodes were plated with an additional gold layer. As a result, the inter-electrode spacing, as measured using atomic force microscopy and conventional microscopy, was reduced to 0.6 μm. The achieved gap spacing is limited by electrode imperfections resulting from the lift-off process. At these imperfections the electrodes become shorted. Additional experiments with wet etched electrodes are expected to yield smaller gap spacings.