Cu-doping effect on structural, optical and photoluminescence properties of Zn_0.96−xFe_0.04Cu_xO (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) nanopowders by sol–gel method

Zn_0.96−xFe_0.04Cu_xO (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) nanopowders have been synthesized by sol–gel method. The synthesized samples have been characterized by powder X-ray diffraction, energy dispersive X-ray spectra, X-ray photoelectron spectroscopy, UV–visible spectrophotometer and Fourier transform infrared spectroscopy. The XRD measurement reveals that the prepared nanopowders have different microstructure without changing a hexagonal wurtzite structure. The calculated average crystalline size increases from 20.9 to 22.1 nm for x = 0 to 0.02 then gradually decreases to 18.2 nm for x = 0.10 which were confirmed by SEM and TEM micrographs. The change in lattice parameters, micro-strain, and shift of X-ray diffraction peaks towards lower angles and increase of energy gap reveal the substitution of Cu²⁺ ions into Zn–Fe–O matrix. X-ray photoelectron spectroscopy study described the increase of oxygen vacancies with increase of Cu concentrations, which was found to enhance the green emission. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra. Photoluminescence spectra of Zn_0.96−xFe_0.04Cu_xO system shows that the blue shift in NBE ultraviolet emission from 389 to 369 nm and the same blue shift in green band emission from 552 to 535 nm with enhancing intensity confirms the substitution of Cu into the Zn–Fe–O lattice. Cu-doped Zn_0.96−xFe_0.04Cu_xO system is appreciable for the fabrication of nano-optoelectronic devices like tunable light emitting diode in the near future.