Characterization of a “solid-state” Microelectrochemical Diode Employing a Poly(vinyl Alcohol)/phosphoric Acid Solid-state Electrolyte: Rectification at Junctions Between WO3 and Polyaniline


The functionalization of an array of eight, closely spaced (∼1.2 μm) Pt or Au microelectrodes each ∼50 μm long, 2 μm wide, and 0.1 μm thick with redox-active WO3 and polyaniline and the electrochemical characterization of the WO3/polyaniline junction are reported. Chips consisting of microfabricated WO3 covering three of the available eight microelectrodes have been analyzed by Auger electron spectroscopy. The remaining five microelectrodes are available for further derivatization with polyaniline or can function as counterelectrodes. By placing a counterelectrode and a Ag quasi-reference electrode directly on the microchip and by coating the assembly with a thin film of poly(vinyl alcohol)/H3PO4 solid polymeric electrolyte, the electrochemical system becomes self-contained. The solid polymer electrolyte is a good room-temperature H+ conductor only when exposed to a H2O-containing atmosphere. Complex impedance studies show as much as a 103 change in H+ conductivity from H2O-saturated to H2O-free gaseous atmosphere above the polymer electrolyte. The changes in conductivity of WO3 upon reduction or polyaniline upon oxidation allow demonstration of solid-state microelectrochemical transistors with these materials. The combination of WO3 and polyaniline on the chip allows demonstration of a microelectrochemical diode. © 1990 American Chemical Society.



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© 1990 American Chemical Society (ACS), All rights reserved.