Hydrogen Gas Sensors Using Anodically Prepared and Surface Modified Nanoporous ZnO Thin Films

High purity Zn was electrochemically anodized to grow nanocrystalline and nanoporous ZnO thin film, which was subsequently surface modified by Pd using electroless chemical dipping method. Two different device configurations e.g., a planar structure and a metal-active insulator-metal (MIM) sandwich structure, both working in Schottky barrier mode were designed, fabricated and tested as a hydrogen sensor. A Pd-Ag alloy was used as catalytic electrode contact for both the planar and MIM (metal-insulator-metal) configurations. Nitrogen and synthetic air were used as carrier gases for hydrogen in separate experiments. A dynamic response of ∼65, response time of 2.2 s and a recovery time of 21.8 s for the planar structures and the corresponding values of ∼62, 1.8 s and ∼14 s were recorded for the MIM structures at an optimum temperature and voltage of 50 °C and 0.5 V. The sensing operation for 16 h showed an excellent stability.