Search

Raman scattering experiments complemented by density functional theory (DFT) calculations of phonon frequencies have been performed to understand the origin of observed high-energy local Raman modes at 2269 cm-1 and 2282 cm-1 on N-plasma treated ZnO nanowires (NWs). We show that these modes increase in intensity with prolonged N-plasma treatment. Our results reveal that the origin of the high-energy Raman local mode is a loosely bound N2 molecule in the vicinity of a zinc vacancy, which according to our latest work acts as a shallow acceptor and leads to the donor-acceptor-pair transition at 3.232 eV [Phys. Rev. B 92, 024103 (2015)]. Moreover the results provide a more thorough description of nitrogen related complexes in ZnO NWs. [ABSTRACT FROM AUTHOR]

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 2.4at%. 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. [Copyright &y& Elsevier]