Holmium (Ho)-coated ZnO nanorods: an investigation of optoelectronic properties

Abstract

In this work, ZnO nanorods were synthesized by a simple and low-temperature hydrothermal method. Their surfaces were coated by Holmium using the drop-coating deposition technique. The morphology and the structural measurements showed that Holmium has coated completely the surface of ZnO; nanorods have hexagonal structure and their average diameter is about 500 nm, length up to 4 µm. The absorption properties result showed that Ho coated ZnO has an intense absorbance in the ultra-violet region and the optical band gap energy (Eg) of Ho-coated ZnO was calculated and was found to be 3.35 eV. The photoluminescence (PL) spectrums of nanostructures were analyzed to survey the effect of Ho coating on the optical luminescence properties of ZnO, finding that the ZnO nanorods have a strong visible emission centered around 560 nm, while Ho-coated ZnO nanorods have luminescence peaks in the UV and visible region. The excitations wavelength effect revealed that the blue emission can be excited by energies lower than the band gap of ZnO (3, 37 eV). Thus, it indicates that the Ho-coated ZnO nanorods can increase the absorption of UV light, which may hold great promise for the development of the optoelectronic applications.