The structural and optical properties of Volmer-Weber-type ZnO nanorods

Abstract

Volmer-Weber-type ZnO nanorods (VW ZnO NRs) were fabricated by using a hybrid method combined with RF sputtering and hydrothermal methods. The structural and optical properties of VW ZnO NRs were investigated by using synchrotron X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that VW ZnO NRs showed wurtzite structure and were vertically standing on a substrate with a compressive stress from the substrate that can be reduced by annealing. In the micro-Raman study, a forbidden E1(LO) mode in a bulk ZnO was observed in VW ZnO NRs due to the many edges in NR structures. It was also confirmed that VW ZnO NRs have a wurtzite structure by observing E 2 low and E2 high peaks. In the PL spectra, VW ZnO NRs showed a broad emission in the visible range, especially yellow emission, with a weak UV emission. The UV emission was monotonously enhanced on increasing the annealing temperature. The yellow emission was enhanced in the annealed sample at 200 °C due to an evaporation of hydroxyl groups (OH-) on the surface of VW ZnO NRs. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.