Nanoporous Silicon Thin Film-Based Hydrogen Sensor Using Metal-Assisted Chemical Etching with Annealed Palladium Nanoparticles.

This article reports a nanoporous silicon (Si) thin-film-based high-performance and low-power hydrogen (H) sensor fabricated by metal-assisted chemical etching (MaCE). The nanoporous Si thin film treated with Pd-based MaCE showed improvement over a flat Si thin film sensor in H response (Δ/ = 4.36% → 12.4% for 0.1% H). Furthermore, it was verified that the combination of thermal annealing of Pd and subsequent MaCE on the Si thin film synergistically enhances the H sensitivity of the sensor by 65 times as compared to the flat Si thin film sensor (Δ/ = 4.36% → 285% for 0.1% H). This sensor also showed a very low operating power of 1.62 μW. After the thermal treatment, densely packed Pd nanoparticles agglomerate due to dewetting, which results in a higher surface-to-volume ratio by well-defined etched holes, leading to an increase in sensor response.