Study of dielectric relaxation processes in printable zinc oxide films on transparent substrates

Abstract

AC impedance spectroscopic measurements have been performed on sol–gel derived zinc oxide (ZnO) films on transparent fluorine-doped tin oxide coated glass substrates in the frequency range 10⁻² to 10⁶ Hz over the temperature range −185 to +25 °C (88–298 K). The relaxation behaviour of the nanocrystal line ZnO thin film can be described in terms of the Debye model giving an interpretation of the semi-circular relaxation phenomenon within the given temperature range. Two different relaxation times were obtained from impedance (Z) and electric modulus (M) studies of the devices and the multiple hopping of charge carriers between trap sites in grain and grain-boundary regions is believed to be responsible for charge transport. The values of activation energies for trap levels obtained from AC conductivity study are 0.0153 and 0.0487 eV which are close to the activation energies obtained from DC electrical measurement for temperature region between 88 and 178 K and 179 and 298 K, respectively.