Effects of bath temperature on the morphology of ZnO nano-rods and its optical properties

• We control the morphology and growth direction during ZnO growth by changing water bath temperature.
• We are using the ECD method in a two-electrode cell without any other supporting electrolyte.
• The morphology is best at 85 °C water bath temperature.

ZnO nano-rod arrays with different morphologies were vertically grown on indium-tin oxide (ITO) glass substrates using the electrochemical deposition (ECD) method processing in a two-electrode cell. The bath temperature plays a key role in the growth process. The effect of growth bath temperature was studied with respect to the morphological, structural, and photoluminescence properties of the ZnO nano-rod arrays. The ZnO nano-rod arrays fabricated at 85 °C bath temperature had the best morphology, structural and optical qualities. The clear lattice fringes in the image of high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) showed that a single-crystal structure of ZnO nano-rods with the growth direction along the [002] direction. The top-sectional field emission scanning electron microscopy (SEM) images results revealed that the bath temperature played a key role in the morphology evolvement of the ZnO nano-rods. A sharp peak in the UV region and a weak broad peak in the visible region between 400 and 500 nm were shown in the room temperature photoluminescence (PL) spectra of the samples, suggesting that the ZnO nano-rod arrays with high-quality crystals were obtained. This synthesis method provided a low cost and easy route for the preparation of 1D ZnO nanostructures.