Tunability of Pd-nanogapped H₂sensors made on SiO₂-coated Si micropillar arrays

A micro-nano hybrid technique is implemented to produce Pd-nanogapped gas sensors with tunable H2sensing properties. The basic idea is to deposit a Pd film on a SiO2-coated Si micropillar array. By adjusting the SiO2-gap size and Pd film thickness, one can tune the size and distribution of the nanogaps in the Pd film precisely to achieve the desired gas sensing performances. With this approach, sensors of three different configurations were fabricated to go through the tests for 0–6% H2at 40 °C. Different sensor types were found to give respective dynamic range of detection, shape of sensor response and mode of operation. The sensor type designed to contain an Au/Cr buffer layer exhibits a detection limit of 20 ppm of H2. The method is scalable and compatible with Si-based micromachining processes. The design is also extendable for making multi-sensor arrays. The physical mechanisms involved in controlling the sensor properties are proposed and discussed.