Structural, FTIR and photoluminescence studies of Cu doped ZnO nanopowders by co-precipitation method

Abstract

Cu doped ZnO (Zn1−xCuxO, x=0, 0.02, 0.04 and 0.06) nanopowders have been synthesized by co-precipitation method and annealed at 500°C for 2h under Ar atmosphere. The synthesized samples have been characterized by powder X-ray diffraction, energy-dispersive analysis X-ray (EDAX) spectra, UV–Visible spectrophotometer and Fourier transform infrared (FTIR) spectroscopy. The XRD measurement reveals that the prepared nanoparticles have different microstructure without changing a hexagonal wurtzite structure. The calculated average crystalline size decreases from 22.24 to 15.93nm for x=0 to 0.04 then reaches 26.54nm for x=0.06 which is confirmed by SEM micrographs. The change in lattice parameters, micro-strain, a small shift and broadening in XRD peaks and the reduction in the energy gap from 3.49 to 3.43eV reveals the substitution of Cu2+ ions into the ZnO lattice. Hydrogenation effect improves the crystal quality and optical properties. It is proposed that Cu doping concentration limit is below 6% (0.06) molar fraction which is supported by the detailed XRD analysis and the derived structural parameters. This Cu concentration limit was proposed as below 5% by previous studies. The presence of functional groups and the chemical bonding is confirmed by FTIR spectra. PL spectra of the Zn1−xCuxO system show that the shift in near band edge (NBE) UV emission from 398 to 403nm and a shift in green band (GB) emission from 527 to 522nm which confirms the substitution of Cu into the ZnO lattice.