Electrical characteristics of CO2-sensitive diode based on WO3 and IrO2 for microsensor applications

Abstract

Devices based on the contact of sputtered WO3 and IrO2 that are covered by an HCO3--containing polymer exhibit reversible and reproducible CO2-dependent, diodelike current rectification at 1 atm and room temperature. The gain or loss of current in the forward direction as a function of CO2 concentration is found to be tunable by controlling the thickness ratio of the WO3 and IrO2 films. The rectification mechanism is uniquely governed by the thermodynamic free energies; this is the key to the durability previously not attainable using conventional diodes in microsensor applications. These diodes are useful as a basis of construction for durable microsensors operating in gases or liquids.