Fabrication of ZnO nanorods for NO2 sensor applications: Effect of dimensions and electrode position

In this study, zinc oxide (ZnO) nanorods were fabricated by using hydrothermal method and resistive type nitrogen dioxide (NO2) sensing properties of the nanorods were investigated depending on temperature, NO2 concentration, electrode position and the dimension of the nanorods. To produce ZnO seed layer, zinc acetate solution was coated on a glass substrate by using spin-coater. ZnO nanorods were grown by changing concentration of solution at 90 °C for 3 h onto seed layer coated substrate. ZnO nanorods were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was observed that the diameters of ZnO nanorods were approximately 30 nm, 60 nm and 120 nm depending on solution concentration. For gas sensing measurements, interdigitated Au electrodes were coated on top or bottom of ZnO nanorods by using thermal evaporator. All samples were tested against to NO2 in dry air ambient depending on concentration (100 ppb-1 ppm) in the temperature range of 25-200 °C. The highest sensor response was observed for ZnO nanorods that were 60 nm in diameter. The response and recovery times for all sensors decreased with increasing temperature and the sensors were fully recovered above temperature of 100 °C.