Performance Enhancement of Polymer Electrolyte MEIS Hydrogen Sensor by DC-Biasing

DC-biasing was applied as a method to enhance the performance of a capacitive type gas sensor with a polymer electrolyte layer. The sensor was constructed as a metal-electrolyte-insulator-semiconductor structure with a polymer electrolyte layer deposited on a Si-substrate with SiO₂-dielectric layer and aluminum back electrode. The electrolyte was prepared from polyvinyl chloride polymer dissolved in water with adding H₃PW₁₂O₄₀ to the mixture making it proton conductive. The device was finalized with a platinum top electrode. The sensor was shown to be sensitive to H₂ with detection limit below 100-ppm concentrations in synthetic air at room temperature. The sensor was tested using ac voltages with 250-mV amplitude and frequency from 1 to 100 kHz. In addition, by dc biasing the device with voltages up to 2 V during the capacitive measurements, the response, and sensitivity of the sensor were increased by 70% and 50%, respectively, at the optimal measurement frequency (5 kHz).