Low temperature electrochemical deposition of nanoporous ZnO thin films as novel NO2 sensors

The nanoporous ZnO thin films were prepared on Ti substrate by the low temperature, one-step electrochemical deposition for a novel NO2 sensor. The porous structure of the prepared thin films can be controlled by the added amounts of eosin Y in the deposition bath. The crystalline structure and morphologies of ZnO thin films were characterized. The effect of the surface structure and defects of ZnO thin films on the adsorption of oxygen and the gas sensing performance were investigated. The sensing test results indicate that the ZnO porous thin films have high sensitivity toward NO2. On the other hand, the response to NO2 is higher than that to CH4 and CO at relative low temperature indicating its good sensing selectivity. The intrinsic sensing characterization is attributed to the native defects in ZnO because the relative content of donors is more than that of the acceptors, which was confirmed by the photoluminescence analysis. This work presents a new possibility and usefulness of such electrochemically prepared ZnO porous thin film and can give rise to interesting option for developing other novel sensors.