Improvement of gas-sensing performance of ZnO nanorods by group-I elements doping

In the present work, a comparative study of gas sensor performance of group-I-doped (Na- and K-doped) ZnO nanorods to ethanol was carried out for the first time. The nanorods were grown on SiO2/Si substrates by a thermal evaporation method, using a tube furnace. X-ray photoelectron spectroscopy (XPS) results confirmed that the K and Na were doped in the ZnO nanorods. Furthermore, the XPS spectra indicated that the K-doped ZnO nanorods were grown by more oxygen vacancy compared with the Na-doped ZnO nanorods. Room temperature photoluminescence results confirmed the XPS results about oxygen vacancy level of the doped samples. The doped ZnO nanorods showed excellent gas-sensing performance against ethanol in comparison with the undoped ZnO nanorods. The K-doped ZnO nanorods revealed a high gas sensing at the operating temperature of 300 °C, while the operating temperature of the Na-doped was 280 °C. Moreover, the response and recovery time of the doped samples were shorter than those of the undoped sample. The enhanced gas-sensing performance of doped ZnO nanorods is attributed to the larger amount of oxygen vacancy in the doped ZnO nanorods. Furthermore, group-I-doped ZnO nanorods performed good selectivity compared with the undoped ZnO nanorods.