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

Abstract Titanium oxide (TiO 2 ) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO 2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen 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 TiO 2 coating by ALD. The nucleation and growth of TiO 2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO 2 nuclei decreased and the quantity of TiO 2 nuclei increased, resulting in the growth of a highly uniform and dense TiO 2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 10 21 atom cm −2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO 2 was as low as 3.0 × 10 −25 cm 3 /atom, which is one order less than that of the standard POLYIMIDE-ref Kapton ® film.