Impedance spectroscopy and sensors under ethanol vapors application of sprayed vanadium-doped ZnO compounds

Abstract

Thin films of vanadium-doped zinc oxide with different vanadium-doping levels (0, 1, 2 and 3at%) were deposited on glass substrates by employing an inexpensive, simplified spray technique using at relatively low substrate temperature (460°C). The effect of V doping on the structural, morphological and optical properties of the films was investigated by Mhamdi et al. (2013). The X-ray diffraction analysis shows that the films were well crystallized in würtzite phase with the crystallites preferentially oriented toward (002) direction parallel c-axis. As also that the average particle size along the surface of the films decreases with increasing of concentration of vanadium. In this work we study the AC and DC conductivity and gas sensor application on ZnO:V thin films. The dielectric properties of ZnO:V thin films were studied by means of complex impedance spectroscopy and frequency dependence of conductivity measured from the impedance data at a range of frequency intervals between 10Hz and 13MHz with a temperature between 355 and 445°C. The frequency dependence of the dielectric constant ɛ′, dielectric loss ɛ″, loss tangent (tanδ) and AC electrical conductivity (σAC) of the layers was subsequently investigated. In literature, we have shown in previous papers that structural and surface morphology of ZnO thin films, prepared by spray, plays an important role in the gas detection mechanism. In this article, we have studied the response evolution of ZnO:V sensors ethanol versus time and working temperature, relative doping and the concentration of the ethanol vapor.