Hydroxylation of organic substrate surfaces for the atomic layer deposition of Al2O3 thin films

The hydrophilicity of flexible organic substrates has a certain influence on the quality and performance of Al2O3 films prepared by atomic layer deposition (ALD). Surface treatment and other methods to improve the hydrophilicity of the substrate can make it more suitable for deposition of Al2O3 film. In this paper, polyimide organic substrates were hydroxylated by dry and wet hydroxylation. The water contact angle of the hydroxylated surfaces was measured using Droplet shape analyser. The results show that the water contact angle of the organic substrate surface after dry and wet hydroxylation is significantly reduced, and the hydrophilicity of the substrate is enhanced. Al2O3 thin films were deposited by ALD on the surfaces of untreated and hydroxylated substrates, and the effects of hydroxylation on the uniformity and growth rate of the films were investigated. The Al2O3 films were characterized using scanning electron microscopy and atomic force microscopy. When 30 ALD cycles were performed at 200 °C, the results show that the Al2O3 clusters grown on the surface of the dry hydroxylated substrate are denser, which is favorable for the growth of continuous films. Comparative study of Al2O3 films deposited at different temperatures and number of cycles showed that at 200 °C, the roughness Ra of the deposited films decreased to 0.55 nm with the increase in the number of ALD- Al2O3 cycles, and the films were uniform and smooth, no subsurface growth was observed. This study provides a feasible process route for the preparation of high-performance Al2O3 films on organic substrates, which is of great significance in the field of flexible electronic devices and functional coatings.