Structural, morphological and spectroscopic investigation of Mn doped Zn_0.96Cu_0.04O nanoparticles

Abstract

Zn_0.96−xCu_0.04Mn_xO (0 ≤ x ≤ 0.04) nanoparticles were synthesized by sol–gel method. The X-ray diffraction pattern indicated that doping of Mn and Cu did not change the ZnO hexagonal wurtzite structure. The Mn doped nanoparticles had smaller average crystalline size than un-doped Zn_0.96Cu_0.04O nanoparticles due to the distortion in the host ZnO lattice. This distortion prevented the subsequent growth and hence the size reduced by Mn doping. The changes in lattice parameters, average crystalline size, peak position and peak intensity confirmed the Mn substitution in Zn–Cu–O lattice. The dielectric constant also varied by depend the size of the nanoparticles. The change in morphology by Mn-doping was studied by scanning electron microscope and the presence of compositional elements such as Mn, Cu and Zn with their nominal stoichiometry was confirmed by energy dispersive X-ray spectra. The optical absorption and band gap were changed with respect to both compositional and size effects. The band gap was initially increased from 3.65 to 3.73 eV at 1 % of Mn doping, while decreasing trend in band gap was noticed for further increase of Mn. The band gap was decreased from 3.73 to 3.48 eV when Mn concentration was increased from 2 to 4 %. Presence of chemical bonding and purity of the nanoparticles were confirmed by FTIR spectra. The Mn and Cu co-doping increased the charge carrier density in ZnO which led to increase the dielectric constant.