Highly sensitive dual-FET hydrogen gas sensors with a surface modified gate electrode

Abstract

Low-power dual-FET type H2 sensors were fabricated, and surface modification techniques were developed to control the morphology of the catalytic metal gate. The differential outputs between the sensing FET and the reference FET were preserved even under a thermal change (from 50 °C to 150 °C) due to the same dependence of the electrical characteristics. The proposed sensor design showed low power consumption (45.5 mW 150 °C) by complete heat isolation. The sensors gave stable responses to H2 gas over a wide temperature range, and the temperature of optimal response in micro-heater operation was approximately 150 °C. The surface of the catalytic metal gate was modified with solution based methods using a poly-styrene (PS) nano-beads suspension. The maximum drain current changes of the FET sensors with a nano-bumpy Pd film and a flat-surface Pd film were 164.6 μA and 128.2 μA to 5000 ppm hydrogen, respectively. The gas sensing characteristics of the FET sensor with the nano-bumpy Pd film were much higher than those of the FET sensor with the thin film due to the nano-porosity of the catalytic metal film.