Cobalt-doped ZnO nanowires on quartz: Synthesis by simple chemical method and characterization

The synthesis of cobalt-doped ZnO nanowires is achieved using a simple, metal salt decomposition growth technique. A sequence of drop casting on a quartz substrate held at 100 °C and annealing results in the growth of nanowires of average (modal) length ∼200 nm and diameter of 15±4 nm and consequently an aspect ratio of ∼13. A variation in the synthesis process, where the solution of mixed salts is deposited on the substrate at 25 °C, yields a grainy film structure which constitutes a useful comparator case. X-ray diffraction shows a preferred [0001] growth direction for the nanowires while a small unit cell volume contraction for Co-doped samples and data from Raman spectroscopy indicate incorporation of the Co dopant into the lattice; neither technique shows explicit evidence of cobalt oxides. Also the nanowire samples display excellent optical transmission across the entire visible range, as well as strong photoluminescence (exciton emission) in the near UV, centered at 3.25 eV.

► Co-doped ZnO nanowires (200×15 nm) synthesized by simple solution-based technique.
► Preferential growth direction is (0001).
► Successful incorporation of Co is corroborated by XRD, Raman, optical absorption.
► Nanowires show greater optical transmission and exciton luminescence than grainy film