Sensitivity Enhancement of ZnO Nanorod Gas Sensors with Surface Modification by an InSb Thin Film

Zinc oxide (ZnO) nanorods were prepared on sol–gel ZnO seed-coated alumina substrates by a hydrothermal method. A very thin layer of indium antimonite (InSb) was deposited on the ZnO nanorods by a thermal evaporation technique. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were applied to analyze the quality of the ZnO nanorods. XRD results showed that the as-synthesized ZnO nanorods were well crystallized in hexagonal wurzite ZnO. An X-ray photoelectron spectroscopy (XPS) study confirmed the deposition of InSb on the ZnO nanorods. The activation energies of sensors fabricated from ZnO nanorods and InSb-deposited ZnO nanorods were calculated. It was found that the activation energy of the InSb-deposited ZnO nanorods was very small. The sensitivity of the sensors towards acetone gas was measured at concentrations of 500–5,000 ppm and at operating temperatures ranging from 200 to 350 °C. The sensitivity of the InSb-deposited ZnO nanorod sensor was much higher than that of the ZnO nanorod sensor. The optimum temperature of the sensors was found to be 300 °C.