A method of color modulation based on porous alumina and atomic layer deposition

By modeling and analyzing porous alumina (PA), a method to modulate the colors of PA templates is proposed, which is based on the preparation of PA templates and the atomic layer deposition (ALD) technique. Referring to the experimentally prepared PA samples, theoretical simulations are carried out for a series of PA templates with the same hole-diameter and hole-interval, but with different hole-depths. The relationship between the modulated colors and the hole-depths are thus disclosed. By controlling the time of anodization in oxalic acidsolution, two PA samples with different hole-depths (296 nm and 373 nm) were prepared, both with an average hole-diameter of 40 nm and an average hole-interval of 100 nm, respectively. ALD processing is then applied to deposit a layer of Fe2O3 film with total thickness of 16.8 nm on these samples. It was experimentally observed that the processed PA samples show different colors which change with hole-depths. The experimental results are in good agreement with the theoretical simulations, which proves the feasibility of color modulation with this method.