Activation of polyimide by oxygen plasma for atomic layer deposition of highly compact titanium oxide coating

Titanium oxide (TiO₂) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO₂coating on polyimide by atomic layer deposition (ALD), the polyimide was activated byin situoxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO₂coating by ALD. The nucleation and growth of TiO₂were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO₂nuclei decreased and the quantity of TiO₂nuclei increased, resulting in the growth of a highly uniform and dense TiO₂coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 10²¹atom cm^-2atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO₂was as low as 3.0 × 10^-25cm³/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton^®film.