Complex electrical impedance and modulus characterizations of ZnO:Sn thin films in a wide temperature range

Abstract

In this study, pure zinc oxide (ZnO) and tin-doped zinc oxide (Zn_1−xSn_xO) thin films were synthesized using successive ionic layer adsorption and reaction (SILAR) method in 40 cycles with doping ratios x = 0.05, 0.10, 0.15, and 0.20. Subsequently, structural, optical, and electrical characteristics of all synthesized thin films were properly investigated by the appropriate techniques. For structural characterizations, X-ray diffraction (XRD) technique was employed, and the data demonstrated the appropriate hexagonal wurtzite structure of the synthesized thin films and predicted the decrease of crystallite size with Sn doping. Likewise, optical characterizations were carried out through ultraviolet–visible (UV–Vis) technique, and the data showed good transparency of ZnO thin film and confirmed the increase in transparency and bandgap upon Sn doping. Additionally, to probe the electrical aspects of the synthesized thin films, impedance, modulus, and conductivity analyses were carried out as a function of frequency in a wide temperature range (450–750 K). The results demonstrated the critical effect of temperature and Sn doping ratio in ZnO thin films. At high enough temperatures, inductive effects became evident in the low-frequency region of all the thin films. And at all temperatures, 5 wt%- and 10 wt%-doped films exhibited extreme responses in the investigated doping range, where the former and the latter showed, respectively, highest and lowest conductivity as well as lowest and highest possibility of grain effects in the film structure. This behavior was confirmed using two different analysis techniques with two separate data sets, (Z, θ) and (C, G).