Growth and atomic oxygen erosion resistance of Al2O3-doped TiO2 thin film formed on polyimide by atomic layer deposition

Abstract

Polyimide (PI) coated with atomic layer deposition (ALD) thin films shows promising potential for applications in extreme environments. To achieve a high quality ultrathin ALD coating on the PI surface, Al-doped ALD-TiO₂ (ATO) films were deposited on the alkaline hydrothermally activated PI surfaces. The nucleation and growth of ATO films were studied by XPS monitoring and SEM observation. The incorporation of aluminum introduced additional active sites that acted as a seed layer, promoting the adsorption and growth of titanium oxide. This effectively compensated for the defects in the TiO₂ film, resulting in the formation of a continuously growing conformal film on the PI surface. After 200 ALD cycles, the ATO film deposited on PI exhibits excellent water vapor barrier properties and significant resistance to atomic oxygen (AO) erosion. When exposed to an AO flux of 1.4 × 10²² atom per cm², the erosion yield of the PI coated with 200 ALD cycles of ATO film was as low as 2.4 × 10⁻²⁶ cm³ per atom, which is two orders less than that of the standard polyimide-ref Kapton® film.