The effect of pH condition on Zinc Oxide growth fabrication using Flexible Substrate

Abstract

Zinc Oxide (ZnO) nanostructures using glass substrate exhibit attention-grabbing properties together with high chemical process efficiency and robust adsorption ability. Various initiatives have been undertaken to develop ZnO growth on flexible substrates to replace the conventional glass substrate as it can be utilized as flexible optoelectronic and flat panel displays. This research work focused on the effect of pH condition on ZnO growth fabrication using a flexible substrate. In this study, ZnO thin films were deposited on ITO/PET substrate by a spin coating sol-gel method. The precursor solution was prepared by dissolving Zinc Acetate Dihydrate (ZnAc) and Diethanolamine (DEA) in Deionized Water (H2O) and Iso-Propanol (2-PrOH). ZnO thin films were obtained after pre-heating the spin-coated thin films at 100 °C for 5 minutes after each coating until five layers obtained. Subsequently, growth solutions were obtained from Hexamethylenetetramine (HMT), Zinc Nitrate-6-Hydrate (ZnN) and Sodium Hydroxide (NaOH), pH adjuster with final solution pH values of 6, 8, 10, 12 and 14. After that, hydrothermal synthesis was done with 90 °C for 4 hours. XRD results indicated high intensity on (101) plane, which increased until the optimum pH level of 10 but decreased due to high alkalinity. Meanwhile, FESEM demonstrated hollow nanotube hexagonal wurtzite, nanoneedle-like nanorods, dendrite nanoparticles with nanoflower-like morphology as the pH value increased from 6 to 14. The optical band gap values obtained were in the range of 3.89 to 3.96 eV as pH 10 sample had the highest value. In conclusion, it is proven that the pH condition of the growth solution influences the ZnO growth on ITO/PET substrate.