Vol.:(0123456789) 1 3 Applied Physics A (2019) 125:615 https://doi.org/10.1007/s00339-019-2911-3 Rietveld refnement of X‑ray difraction, impedance spectroscopy and dielectric relaxation of Li‑doped ZnO‑sprayed thin flms Mohamed Salah 1  · Samir Azizi 1  · Abdelwaheb Boukhachem 2  · Chokri Khaldi 1  · Mosbah Amlouk 2  · Jilani Lamloumi 1 Received: 22 May 2019 / Accepted: 6 August 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract In this paper, thin flms of lithium-doped zinc oxide (ZnO: Li) were prepared by spray pyrolysis in a monophase hexagonal wurtzite structure as shown by X-ray analysis. Rietveld refnement of the X-ray difraction diagram was applied to calculate the crystalline structure parameters. Impedance spectroscopy, electrical conductivity and dielectric measurements, at various temperatures 340–440 °C and in a frequency spectrum from 5 Hz to 1 MHz, were performed using the EC-Lab V10.12 sys- tem. During the electrical conduction processes in the sample, the physical parameters of ZnO:Li thin flms such as dielectric constant, relaxation frequency and electrical conductivity σ ac and σ dc , were examined. In addition, AC conductivity analysis resulted in a power law (σ ac = ω s ). Obviously, the temperature dependence of the exponent s ftted well with the correlated barrier hopping (CBH) model proposed by Elliott. Finally, the dependence of conductivity and dielectric constants with frequency and temperature was discussed. 1 Introduction Zinc oxide (ZnO) is an II–VI semiconductor material widely used in diferent applications due to its low cost [1–4], non- toxicity [5–8] and bio-compatibility [9–12]. Moreover, it is quite abundant and can be deposited in various ways [13–17]. In addition, ZnO has been the focus of intensive studies in recent decades because of its wide range of appli- cations (sensors [18–22], light-emitting devices [23–25], solar cell electrodes [26–31] and optical waveguide devices [32–34] and its semiconductor optoelectronic properties [35, 36], such as its high transparency to visible light [37–39]. Its direct band gap is about 3.3 eV at room temperature [40, 41] with a high binding energy of about 60 meV and an intrinsic conductivity of type n [42]. In fact, the doping of ZnO thin flm is carried out to enhance the microstructural, optical and electrical performances [43–47]. Indeed, the choice of the dopant element depends on the required application. It is well established that the physical characteristics of nano- materials are afected by the size and morphology of nano- particles. As a result, various nanostructured morphologies were synthesized for diferent applications. The increase in the surface/volume ratio due to the decrease in the size of the crystallites allows surface defects to play an important role in all surface phenomena (gas adsorption [48–51], wettabil- ity [52–54], photocatalytic activities [55–58]…). Moreover, it is well understood that a rise in the size of crystallite can afect the optical properties of oxide thin flms (gap optics, transparency) [59] as well as their electrical conductivi- ties [60]. Vishwas et al. [61] reported electrical and micro- structural investigations of zinc oxide flms elaborated by the sol–gel method and annealed at diferent temperatures (200–500 °C). They concluded that the annealing tempera- ture afects substantially the morphostructure of ZnO and consequently its electrical properties. Fu et al. [60] discussed the optical, structural and electrical investigations of Cr- doped ZnO flms elaborated by the sol–gel method. They noticed that ZnO resistivity decreased as the crystallinity of the flm increased, which proves the improvement of electri- cal properties by increasing the size of the crystallites. The same behaviour was observed by Kumar et al. [62] on Cd- doped ZnO thin flms grown by reactive DC magnetron sput- tering. The electrical resistivity of the flms was diminished by cadmium doping. The authors found that, at a higher Cd * Mohamed Salah mohamed.salah@esstt.rnu.tn * Samir Azizi azizi_samir@yahoo.fr 1 Université de Tunis, ENSIT, LR99ES05, 1008 Montfeury, Tunisia 2 Faculté Des Sciences de Tunis, Unité de Physique Des Dispositifs à Semi-Conducteurs, Université de Tunis El Manar, 2092 Tunis, Tunisia