Understanding the influence of stabiliser concentration on the formation of high quality In 2 O 3 thin films Aysha Riaz , Anna Regoutz Department of Chemistry, University College London, 20 Gordon Street, WC1H 0AJ In 2 O 3 thin films have been studied extensively as they are currently the benchmark parent system for transparent conducting oxides (TCOs) for both optical and electronic device applications. Whilst TCOs are well established for conventional applications, a future area of application is in flexible electronics, which rely on the optimisation of low-cost, solution-based, environmentally friendlier processing methods such as the sol-gel process. The advantage of sol-gel based deposition approaches is their simplicity, requiring an indium-based precursor, solvent, and stabiliser only and can be performed on the bench without the need of vacuum equipment. This enables easier scale-up for large area flexible applications and ensures compatibility with a wide range of substrates (e.g. polymers). However, to produce high quality films needed to achieve peak performance of the oxide thin films, a deeper understanding of the chemistry occurring in the deposition solution is essential. A core challenge with sol-gel processes is their sensitivity to a wide range of synthesis parameters, with e.g. changes in temperature and concentration easily destabilising the solution. A stabiliser is routinely added to the solution to help regulate the hydrolysis reactions taking place, through competitive chelation and alteration of the pH. However, the role of the stabiliser is complex and rarely commented on or fully explored. Here, an investigation into how the amount of stabiliser monoethanolamine (MEA) affects the quality of In 2 O 3 thin films was carried out. By using a combination of XPS, IR and UV-vis the progression of aging of a sol-gel solution was followed across a 24-hour period for varying ratios of MEA to indium content. The results allow to follow the reactions between MEA, solvent, and indium nitrate precursor to determine at which point the solutions were at their optimum for thin film deposition. Additionally, the optimum MEA concentration for the production of the best quality In 2 O 3 thin films could be determined through comparison of surface roughness and film thickness from AFM and ellipsometry, as well as surface chemistry from XPS. Overall, this work delivers a systematic study of the influence of stabiliser concentration on the production of high quality metal oxide films providing the fundamental understanding to select the best synthesis conditions. This facilitates the optimisation of deposition processes and future implementation for large scale industrial deposition pathways for flexible electronics.
P107F
Made with FlippingBook Learn more on our blog