One dimensional (1-D) signatures of nanopillars and nanowires in niobium doped zinc oxide (NZO) thin films prepared by aerosol assisted chemical vapour deposition (AACVD)

Abstract

Abstract We report for the first time a facile synthesis of niobium (Nb) doped (1-D) ZnO nanopillars and nanowires by aerosol assisted chemical vapour deposition with improved structural and optical properties. The micro structural, vibrational and optical properties of Nb-doped ZnO were investigated by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM)/Energy dispersive spectroscopy (EDS) and UV–Vis spectroscopy (UV/VIS). The results presented show that Nb doping and solvent choice can effectively control the growth of ZnO nanostructures as well as their reproducibility. The XRD results revealed that the highest estimated crystallite size of Nb doped ZnO was found to be 4.7 nm from depositions conducted in methanol and 5.4 nm from depositions conducted in toluene for 0.2 M% Nb doping. It is further explored that with an increase of Nb content, ZnO films show poor crystallinity with preferential orientation along the 0 0 2 plane. The change in morphology and local structure of ZnO also led to variations in the vibrational properties of the materials. Upon Nb doping, the A1 (LO) mode of ZnO was found to red shift and broaden, whereas a blue shift was found for the 2A1 (LO), 2E1 (LO) and 2LO vibrational modes. The UV–Visible spectroscopy of Nb doped ZnO revealed that excellent visible transmittance (∼89%) was achievable and witnessed an increase in band gap from 3.3 eV to 3.5 eV with increased Nb doping.