Design of a thin film for optical applications, consisting of high and low refractive index multilayers, fabricated by a layer-by-layer self-assembly method

Anti-reflection (AR) thin film with high and low reflective index layers was successfully fabricated by a layer-by-layer (LBL) self-assembly method. For the deposition of high refractive index layer, poly(diallyldimethylammonium chloride) (PDDA) and titanium(IV) bis (ammonium lactato) dihydroxide (TALH) were alternatively assembled and then, annealed at 200 °C for 5 h. The average thickness of (PDDA/TALH) was determined to be 3.0 ± 0.15 nm and the refractive index was n = 2.2 at 550 nm. Poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) were assembled on high refractive index layer for the deposition of low refractive index layer. The average thickness of (PAH/PAA) was determined to be 4.6 ± 0.1 nm and the refractive index was n = 1.51 at 550 nm. The prepared AR thin film was assembled from 21 bilayers of PDDA/TALH and 20 bilayers of PAH/PAA and the thickness control was achieved with nano-scale precision. The thickness and surface roughness of AR thin film were 155 ± 3 and 6.5 nm, respectively. This AR thin film showed the maximum transmittance (99%) and the minimum reflection (0.04%) around 550 nm in wavelength.