Influence of isovalent Cd doping concentration and temperature on electric and dielectric properties of ZnO films


Altun B., Ajjaq A., ÇAĞIRTEKİN A. O., Er I. K., SARF F., ACAR S.

CERAMICS INTERNATIONAL, vol.47, no.19, pp.27251-27266, 2021 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 47 Issue: 19
  • Publication Date: 2021
  • Doi Number: 10.1016/j.ceramint.2021.06.147
  • Journal Name: CERAMICS INTERNATIONAL
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Chemical Abstracts Core, Communication Abstracts, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.27251-27266
  • Keywords: ZnO, Cadmium, Isovalent doping, Impedance, Dielectric, IMPEDANCE PROPERTIES, NANOPARTICLES, RELAXATION, CADMIUM
  • Gazi University Affiliated: Yes

Abstract

In this study, pure zinc oxide and lightly cadmium doped zinc oxide (Zn1-xCdxO; x = 0.01, 0.03, 0.05 and 0.07) films were synthesized by chemical bath deposition to mainly investigate the possible impact of isovalent (in particular Cd) doping ratio and temperature on their electric and dielectric features. X-ray diffraction patterns revealed that all produced films have a dominance of ZnO hexagonal wurtzite structure with the emergence of a minor CdO cubic phase at x >= 0.03, and predicted the decrease in average crystallite sizes with Cd doping. Cd content in the films was verified by energy dispersive X-ray analysis. Images of scanning electron microscopy revealed the formation of nanorods and spheres on the surface of pure ZnO film which changed to porous/agglomerative spheres with Cd doping. Then a comprehensive electric and dielectric analysis was carried out as a function of frequency in a wide temperature range (300-700 K) using two separate experimental data sets, (Z, theta) and (C, G). The results demonstrated the critical effect of temperature and Cd doping ratio on the electrical and dielectric properties of ZnO films. Among the investigated films, Zn0.97Cd0.03O film recorded highest conductivity and enhanced dielectric properties which was attributed to the equal activation of grains and grain boundaries in the film structure verified by the estimation of activation energies from impedance spectrum. However, the effect of Cd doping on electric and dielectric properties was prominent only below 500 K, beyond which the doping effect became negligible which might be correlated with the effective dominance of grain boundaries at high temperatures as was witnessed by modulus spectrum.