Highly-Sensitive Thermally-Stabilized Palladium Cantilever Nanogap H 2 Sensor

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Abstract
We present a new palladium-based nanogap hydrogen sensor designed for fast, low-concentration H2 detection in environmental monitoring applications. The device consists of a long electrically-conductive low-stress palladium cantilever beam separated by a nanometer-sized air gap from a second cantilever beam of different length placed near the first beam tip thus forming a H2-dependent capacitor. The cantilevers are anchored on top of a thermally-isolated SiN membrane with an integrated microheater that maintains the sensor at constant temperature. When exposed to H2, the capacitor nanogap is reduced resulting in a change in capacitance with H2 sensitivity $S_{\mathrm {H2}} =0.15$ fF/ppm. The sensor shows a consistent response up to $55~^{\circ }$ C with a thermal drift smaller than 0.22 aF/oC and a minimum detectable signal of 10 ppm. The device repeatability was confirmed across 5 consecutive test cycles. Selectivity tests show negligible response to common interfering gases CO, CO2, CH4, water vapor and NH3 ( $S_{i}\lt 5.2\times 1{0}^{-6}$ fF/ppm). The sensor exhibited a response time of approximately 390 ms upon exposure to H2.[2025-0141]
Funding Information
  • U.S. Department of Energy (DOE) Advanced Research Projects Agency-Energy (DE-AR0001836)
  • SEAfloor Self-Sustaining CO2 Assessment Probe Edge (55801195)

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