Palladium/silicon nanowire Schottky barrier-based hydrogen sensors

This work presents the design, fabrication, and characterization of a hydrogen sensor based on a palladium/nanowire Schottky barrier field-effect transistor that operates at room temperature. The fabricated sensor consists of boron-doped silicon nanowire arrays that are contact printed on top of a SiO₂/Si substrate with subsequently evaporated Pd contacts. The fabrication process is compatible with post-CMOS and plastic substrate integration as it can be completed at temperatures below 150 °C with good yield and repeatability. The sensor can reliably and reversibly detect H₂ concentrations in the range from 3 ppm to 5% and has a sensitivity of 6.9%/ppm at 1000 ppm. A response distinguishable from drift and noise is produced in less than 5 s for H₂ concentrations over 1000 ppm and less than 30 s for concentrations over 100 ppm. The sensor settles to 90% of the final signal value in about 1 h at lower concentrations and less than 1 min at 10,000 ppm H₂. Drift over an 87-h measurement period is below 5 ppm H₂ concentration.