Impact of copper doping on the structural, electrical and optical properties of auto-combustion synthesized ZnO nanocomposites

Abstract

Nanocomposites of ZnO have been synthesized by auto-combustion technique to study their electrical (dielectric and direct current), optical, and structural properties by increasing copper content in these composites. Techniques used for characterizing these composite nanoparticles involve X-ray diffraction, scanning electron microscopy, UV–vis spectrophotometry, and photoluminescence spectroscopy. X-ray diffraction patterns suggested hexagonal wurtzite structure of ZnO, which remains unchanged upon increasing the amount of Cu dopant. However, there is a noticeable decrease in the particle size with rising Cu content. Morphology of the crystallites, as observed by scanning electron microscopy, is nearly spherical. Dielectric parameters, including dielectric constant and dielectric loss, decrease, whilst AC conductivity increases with the increase of Cu content as well as with the rise of frequency of the applied alternating biasing field. In addition, DC electrical conductivity is also improved by the enhancement of Cu doping percentage and temperature. These variations of electrical parameters of nanocomposites allow their potential utilization in those devices which are operated at high frequencies. Band gap energy Eg, analyzed by UV–vis spectrophotometer, is noticed to decrease upon rising Cu content from 3.39 eV to 2.46 eV, and depicts a red shift from UV to visible light region. PL emission intensity decreased in the studied light spectrum by increasing Cu content implying that the recombination rate of photo-induced charge carriers decreases effectively. Thus, upon Cu doping reduction in Eg occurs, which along with the reduced recombination rates of photogenerated electrons and holes pairs, becomes a cause of the participation of more and more charge carriers in the photocatalysis process in order to degrade the organic compounds.