Enhanced Electrical and Optical Properties of Cu-Doped ZnO Nanorods Synthesized via Co-Precipitation Method

Abstract

Copper-doped zinc oxide (CZO) nanomaterials were prepared by the co-precipitation method, with a 0.5 M ZnCl₂ solution as the starting material, doped with 0-5 wt.% CuCl₂. The 100 wt.% Cu sample, synthesized without Zn, acts as a pure CuO reference. A 1 M NaOH solution was used as the precipitating agent to adjust the pH to 10. The final product was calcined at 500 °C for 3 h. Morphological analysis using SEM revealed that the CZO samples with 0-5 wt.% Cu exhibited a rod-shaped morphology, whereas the 100 wt.% Cu sample displayed a sheet-like structure with mixed nanoparticles. XRD confirmed the hexagonal wurtzite crystal structure in CZO with no detectable secondary phases, indicating successful incorporation of Cu²⁺ ions into the ZnO lattice. Elemental composition analysis using EDS supported this finding, showing a progressive increase in Cu content from 0.83 wt.% at 1 wt.% doping to 6.03 wt.% at 5 wt.%, accompanied by a corresponding decrease in Zn content. These results suggest that Cu²⁺ ions were effectively substituted for Zn²⁺ within the crystal lattice without forming impurity phases. Optical properties and energy band gap analysis, conducted using fluorescence and ultraviolet-visible spectrophotometry, indicated optimal conditions at 1 wt.% Cu doping. This level corresponded to the lowest band gap energy and the highest electrical conductivity value of 2.71 ´ 10^-3 (Ω·cm)^-1, demonstrating a strong correlation between optical absorption and electrical performance. This study presents a systematic investigation into the effect of low-level Cu doping on the structural, optical, and electrical properties of ZnO nanomaterials.