Fabrication of suspended nanowires for highly sensitive gas sensing

Nanowires suspended above substrates are advantageous as gas sensing materials compared to substrate-bound ones for their better exposure to gas molecules and suppressed undesirable interaction with the substrates. Here, we report a method to fabricate nanowires suspended between electrodes, using suspended carbon nanotubes as sacrificial template. Since all the fabrication steps are scalable process without any exposure of nanowires to photoresist or solvents, the sensors with suspended nanowires could be mass-produced suppressing possible contamination or damage. We could also successfully fabricate suspended nanowires using four different kinds of materials (PdO, NiO, SnO₂, and WO₃). As an exemplary device, hydrogen sensor was demonstrated by forming suspended Pd nanowires between two electrodes, and it could detect 10 ppm hydrogen gas diluted with air at room temperature. This high sensitivity to gas is attributed to the high surface area and small diameter of the suspended nanowires, and the wide variety of material choice with similar morphology of suspended nanowires may be harnessed for the fabrication of highly sensitive gas sensors with diverse sensing targets.