Joule heated and suspended silicon nanowire based sensor for low-power and stable hydrogen detection.

We developed self-heated, suspended, and palladium-decorated silicon nanowires (Pd-SiNWs) for high performance hydrogen (H2) gas sensing with low power consumption and high stability against diverse environmental noises. To prepare the Pd-SiNWs, SiNWs were fabricated by conventional complementary metal-oxide-semiconductor (CMOS) processes and Pd nanoparticles were coated on the SiNWs by physical vapor deposition method. Suspended Pd-SiNWs were simply obtained by etching buried oxide layer and Pd deposition. Joule heating of Pd-SiNW (< 1 mW) enables the detection of H2 gas with faster response and without reduction of sensitivity unlike other Pd based H2 gas sensors. We proposed a H2 sensing model using oxygen adsorption on Pd nanoparticle-coated silicon oxide surface in order to understand the H2 response of Joule heated Pd-SiNW. A suspended Pd-SiNW showed similar transient sensing response with around four times lower Joule heating power (147 μW) than the substrate-bound Pd-SiNW (613 μW). The effect of interfering gas on the Pd-SiNW was investigated and it was found that the Joule heating of Pd-SiNW helps to maintain the H2 sensing performance in humid or carbon monoxide environments.