Fabrication of (PDDA/SiO2) Thin Film by an Applying Voltage Layer-By-Layer Self Assembly Method

(PDDA/SiO2) thin films that consisted of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged SiO2 nanoparticles were fabricated on a glass substrate by an applying voltage layer-by-layer (LBL) self-assembly method. In this study, the microstructure and optical properties of the (PDDA/SiO2) thin films coated on glass substrate were measured as a function of the applied voltage on the Pt electrodes. When 1.0 V was applied to a Pt electrode in a PDDA and SiO2 solution, the thickness of the (PDDA/SiO2)10 thin film increased from 79 nm to 166 nm. The surface roughness also increased from 15.21 nm to 33.25 nm because the adsorption volume of the oppositely charged PDDA and SiO2 solution increased. Especially, when the voltage was applied to the Pt electrode in the SiO2 solution, the thickness increase of the (PDDA/SiO2) thin film was larger than that obtained when using the PDDA solution. The refractive index of the fabricated (PDDA/SiO2) thin film was ca. n = 1.31~1.32. The transmittance of the glass substrate coated by (PDDA/SiO2)6 thin film with a thickness of 106 nm increased from ca. 91.37 to 95.74% in the visible range.