Abstract
The PdNi film hydrogen sensors with Wheatstone bridge structure were designed and fabricated with the micro-electro-mechanical system (MEMS) technology. The integrated sensors consisted of four PdNi alloy film resistors. The internal two were shielded with silicon nitride film and used as reference resistors, while the others were used for hydrogen sensing. The PdNi alloy films and SiN films were deposited by magnetron sputtering. The morphology and microstructure of the PdNi films were characterized with X-ray diffraction (XRD). For efficient data acquisition, the output signal was converted from resistance to voltage. Hydrogen (H2) sensing properties of PdNi film hydrogen sensors with Wheatstone bridge structure were investigated under different temperatures (30 °C, 50 °C and 70 °C) and H2 concentrations (from 10 ppm to 0.4%). The hydrogen sensor demonstrated distinct response at different hydrogen concentrations and high repeatability in cycle testing under 0.4% H2 concentration. Towards 10 ppm hydrogen, the PdNi film hydrogen sensor had evident and collectable output voltage of 600 μV.
Highlights
Hydrogen (H2 ) is one of the most potential and cleanest energy sources [1]
Single-sided polished silicon wafers were selected as the where Uin and U0 are the voltage of external voltage source and initial bias of the Wheatstone bridge, substrates
PdNi alloy film was used as the hydrogen sensing resistor
Summary
Hydrogen (H2 ) is one of the most potential and cleanest energy sources [1]. Considering its low minimum ignition energy and wide flammable range (4–75%), a responsive sensor is essential to detect hydrogen concentration [1,2,3]. Fast and accurate detection of hydrogen concentration is vital to prevent hydrogen leakage when using liquid hydrogen and other aerospace operations in space [2]. Based on different working principles, the hydrogen sensor can be divided into electrical, electrochemical, optical type, work function based, etc. Among those sensors, work function based sensors typically need to work at elevated temperature in order to maintain high sensitivity [2,3]. While resistance based sensors are extensively applied due to ambient working temperature and convenience for measurement [2,4,5,6]
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