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 (H2) 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 H2 response (ΔI/I0 = 4.36% → 12.4% for 0.1% H2). Furthermore, it was verified that the combination of thermal annealing of Pd and subsequent MaCE on the Si thin film synergistically enhances the H2 sensitivity of the sensor by 65 times as compared to the flat Si thin film sensor (ΔI/I0 = 4.36% → 285% for 0.1% H2). 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.