Transport Mechanisms and Dielectric Features of Mg-Doped ZnO Nanocrystals for Device Applications

Abstract

Magnesium-doped zinc oxide “ZnO:Mg” nanocrystals (NCs) were fabricated using a

sol gel method. The Mg concentration impact on the structural, morphological, electrical, and

dielectric characteristics of ZnO:Mg NCs were inspected. X-ray diffraction (XRD) patterns display

the hexagonal wurtzite structure without any additional phase. TEM images revealed the nanometric

size of the particles with a spherical-like shape. The electrical conductivity of the ZnO NCs, thermally

activated, was found to be dependent on the Mg content. The impedance spectra were represented

via a corresponding circuit formed by a resistor and constant phase element (CPE). A non-Debye type

relaxation was located through the analyses of the complex impedance. The conductivity diminished

with the incorporation of the Mg element. The AC conductivity is reduced by raising the temperature.

Its plot obeys the Arrhenius law demonstrating a single activation energy during the conduction

process. The complex impedance highlighted the existence of a Debye-type dielectric dispersion.

The various ZnO:Mg samples demonstrate high values of dielectric constant with small dielectric

losses for both medium and high-frequency regions. Interestingly, the Mg doping with 3% content

exhibits colossal dielectric constant (more than 2 104) over wide temperature and frequency ranges,

with Debye-like relaxation. The study of the electrical modulus versus the frequency and at different

temperatures confirms the non-Debye relaxation. The obtained results reveal the importance of the

ZnO:Mg NCs for device applications. This encourages their application in energy storage.