Revealing the origin of high-energy Raman local mode in nitrogen doped ZnO nanowires

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. Scanning electron microscopy (SEM) image of ZnONWs. (© 2016 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)