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High sensitivity MEMS capacitive hydrogen sensor with inverted T-shaped electrode and ring-shaped palladium alloy for fast response and low power consumption

We report a novel palladium (Pd)-based micro electro-mechanical system (MEMS) capacitive hydrogen gas sensor that has an inverted T-shaped electrode and a ring-shaped Pd alloy layer, which enable high sensitivity and low power consumption. Thanks to these structures, deformation of the membrane as a result of hydrogen absorption can be efficiently transduced to capacitance change. The capacitance change of the proposed sensor is found to be three times larger than that of the conventional structure. Prototype sensors were fabricated by a CMOS-compatible surface micromachining process. The proposed sensor offers a broad design window for attaining high sensitivity. Finally, we show that our sensor provides fast response, is hysteresis-free, and has excellent hydrogen selectivity characteristics despite not employing a heater by using PdCuSi metallic glass.