Hydroxyl radical from UV-irradiated DI water: A simple method for enhancing metal oxide TFTs at low temperature

We have achieved improvements in the electrical properties and low-temperature fabrication of solution-processed amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) using hydroxyl radicals (OH•) generated from ultraviolet-irradiated deionized water (UV-DI). Solution-processed a-IGZO is typically vulnerable due to the high thermal budget required to reduce organic chemical-induced defects arising from the inherent oxidation mechanism. To address this challenge, we generated hydroxyl radicals in deionized water through a UV/O₃ process; these strong oxidants effectively eliminate and decompose organic compounds and are widely used in industrial applications. Hydroxyl radicals were introduced into the IGZO sol-gel mixture, facilitating the production of lower boiling point components and enabling the deposition of IGZO active layers with fewer defects. Thermogravimetric and differential scanning calorimetry (TG-DSC) analysis revealed that the organic materials in the IGZO solution mixture with UV-DI began to decompose at a lower temperature (121.6 °C) than those in the pristine IGZO mixture (144.5 °C). An abrupt weight loss was also observed in the IGZO solution with UV-DI compared to the pristine IGZO solution. Additionally, the saturation mobility and sub-threshold slope of the a-IGZO TFTs made with UV-DI improved compared to the conventional process, increasing from 0.40 to 0.97 cm²/V·s and decreasing from 0.34 to 0.29 V/dec, respectively. These findings suggest that incorporating hydroxyl radicals from UV-DI into the sol-gel solution mixture is a simple method to achieve high-performance TFTs by reducing organic chemical-induced defects through low-temperature processing, potentially influencing future industry practices.