The optical properties of ultra-thin films fabricated by layer-by-layer adsorption process depending on dipping time

The layer-by-layer (LBL) self-assembled polyelectrolytes adsorption process is a very slow process. For the fabrication of low-cost application, fabrication time must be decreased. In this work, we measured optical properties of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) thin films depending on deposition time and added impurities. As dipping time was short from 900 s to 180 s, thickness was almost the same. The reason for this was that adsorption quantity was almost the same between 900 s and 180 s from frequency shift of the quartz crystal microbalance measurement. When dipping time was 900 s and 180 s, the refractive index dispersion curves were different before HCl treatment. However, the refractive index dispersion curves were almost the same after HCl treatment. The total fabrication time of the anti-reflection (AR) film decreased from about 6 h (dipping time 900 s) to 2 h (dipping time 180 s), three times faster. Luminous reflection of the film decreased from 0.5 to 0.2, performing 2.5 times better. We propose a high-performance AR film fabrication method for LBL process by the optimization of the film thickness.