Correlation between the structural and optical properties of Mn-doped ZnO nanoparticles

Highlights: ► Mn-doped ZnO nanoparticles with wurzite structure are prepared by sol–gel. ► Lattice constants along a- and c-axes increase with increasing Mn concentration. ► Optical band gap and band-edge emission energy increase in proportion to a and c. ► Optical properties are mainly influenced by Mn atoms substituting Zn lattice sites. - Abstract: The crystallographic and optical properties of Mn-doped ZnO nanoparticles prepared by a sol–gel process have been investigated by X-ray diffraction, UV-visible absorption spectroscopy and cathodoluminescence microanalysis. X-ray diffraction reveals that the nanoparticles have hexagonal wurtzite crystal structure, with the lattice constants along the a- and c-axes increasing with increasing Mn concentration from 0 to 2.4 at%. For all Mn concentrations in this range, the nanoparticles are essentially free of native point defects so that they exhibit only band-edge luminescence. The optical bandgap and band-edge emission energies for Mn-doped ZnO were found to increase in proportion to the lattice constants. The direct correlation between the bandgap and crystal structure suggests that the band-edge optical properties of Mn-doped ZnO is predominantly influenced by the amount of Mn atoms substituting Zn on the lattice sites.