Preparation and growth mechanism of solidified TiO2 film on polyimide by SILAR at room temperature

In order to further expand the applications of polyimide, titanium oxide (TiO2) was deposited on flexible Kapton substrate by successive ionic layer adsorption and reaction (SILAR) method at room temperature. The growth process was systematically investigated by analyzing the changes of surface structures, film thickness, water wettability and adhesion work during film deposition. The results showed the SILAR TiO2 films growth initializes in an island-like pattern and then gradually transforms into a 2D layered manner after 10 deposition cycles with a growth rate of about 0.5 nm/cycle. With the increase of cycle number, the water wettability and adhesion work increased to ensure the deposition process to be continued. Interestingly, the obtained TiO2 film exhibits weak crystallinity, which is attributed to the surface graphitized structure of Kapton induced by the ultraviolet (UV) activation in ambient. However, no information of the crystalline phase was detected when TiO2 films were deposited on glass or polyethylene (PE) substrates without the special graphit-like structures under the same conditions. Hence, the growth mechanisms as the surface reactions, film formation and continuous growth behaviors of TiO2 film on Kapton substrate were discussed in details. (C) 2019 Author(s).