Morphology and optical properties of ZnO nanorods coupled with metal oxides of various bandgaps by photo-oxidation

Abstract

This work aims to compare the effects on the morphology and optical properties of ZnO NRs (Eg: 3.33 eV) when coupled with metal oxides of various bandgaps, i.e. CuO (Eg: 1.72eV), NiO (Eg: 3.76 eV), and Al2O3 (Eg: 7.07 eV). The amount of metal oxide deposited on the hydrothermally grown ZnO NRs was controlled by the UV irradiation duration of the photo-oxidation process. The deposition of CuO on ZnO NRs produced flake-like structures while Al2O3 deposition created tubular structures. However, when coupled with NiO, ZnO NRs were uniformly covered by a thin layer of NiO without morphological change. The optical bandgap of ZnO NRs was modified slightly from 3.20 eV to 3.17, 3.28 or 3.16 eV after coupling with CuO, NiO, or Al2O3, respectively. The strongest enhancement of IUV/Ivis ratio in the RTPL spectra of ZnO NRs was achieved from Al2O3 coupling.