Rare Earth Oxide Surface Modification of Porous SiO₂ Film Prepared by Atomic Layer Deposition

Broadband transparent films play a pivotal role in various applications such as lenses and solar cells, particularly porous structured transparent films exhibit significant potential.This study investigates a porous SiO 2 refractive index gradient anti-reflective film prepared by atomic layer deposition (ALD).A porous SiO 2 film with gradual porosity was obtained by phosphoric acid etching of Al 2 O 3 /SiO 2 multilayers with gradient Al 2 O 3 ratios, achieving a gradual decrease in refractive index from the substrate to the surface.The film exhibited an average transmittance as high as 97.8% within the wavelength range from 320 nm to 1200 nm.The environmental adaptability was further enhanced by surface modification using rare earth oxide (REO) La 2 O 3 , resulting in formation of a lotus leaf-like structure and achieving a water contact angle of 100.0.These data proved that the modification significantly improved hydrophobic self-cleaning capability while maintaining exceptional transparency of the film.The surface structure of the modified film remained undamaged even after undergoing wipe testing, demonstrating its excellent surface durability.