Impedance Spectroscopy Study of Porous ITO Based Gas Sensor

In this work, Tin-doped indium oxide (ITO) films were prepared by the screen printing technique onto glass substrates then annealed in a furnace at a temperature of 570¡C during 45 minutes. The crystallinity, roughness and morphology of the obtained films were analyzed by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). The energy dispersive spectroscopy (EDX) analysis has been used to determine the atomic composition of the films. The activation energies calculated from the plot of the resistance R versus temperature T indicate that different scattering mechanisms are operative. From Lennard-Jones equation, we can estimate the operating temperature range to activate the chemisorption process that leads to the maximum response of the sensor. AC impedance spectroscopy has been used to investigate the nature of the conduction processes and modeling the sensing mechanisms. All impedance spectra seem to have a single half circle shape without shift along the Z’ axis, the equivalent circuit can be decomposed as a parallel R-C circuit. We found that the resistance and capacitance values depend on temperature and atmosphere change.