Enhanced Gas Sensing Properties of Multiple Networked In₂O₃-Core/ZnO-Shell Nanorod Sensors

The influence of the encapsulation of In₂O₃ nanorods with ZnO on the H₂S gas sensing properties was studied. In₂O₃-core/ZnO-shell nanorods were fabricated by a two step process comprising the thermal evaporation of an 1:1 mixture of In₂O₃ and graphite powders and the atomic layer deposition of ZnO. The core–shell nanorods ranged from 100 to 200 nm in diameter and were up to a few hundreds of micrometers in length. The thickness of the ZnO shell layer in the core–shell nanorod ranged from 5 to 10 nm. Multiple networked In₂O₃-core/ZnO-shell nanorod sensors showed the response of more or less 4 times higher than bare In₂O₃ nanorod sensors to H₂S in a concentration range of 10–100 ppm at 300 °C. The substantial improvement in the response of In₂O₃ nanorods to H₂S gas by the encapsulation with ZnO can be accounted for based on the spacecharge model. Besides the enhanced sensor response, both the response and recovery times of the core–shell nanorods were shorter than those of the bare-In₂O₃ nanorods for any H₂S concentration, respectively.