Preparation of antireflective SiO2 nanometric films

Antireflective nanometric SiO2 films were formed on glass substrates by dip coating from a colloidal SiO2 sol having an average particle size of 9 nm. Withdrawal speed of dip coating was varied between 100 and 200 mm/min with 25 mm increments, and baking temperature of the films was altered between 300 and 550 °C with 50 °C increments. Obtained SiO2 films were in 80–200 nm thickness range. Film thickness was seen to increase with increasing withdrawal speed and to decrease with increasing baking temperature. A maximum light transmittance of 95% was obtained with 4.5% points increase, from the films which were withdrawn at 100 mm/min and baked at 450 or 500 °C. It was seen from SEM observations that the films exhibited full coverage on glass surface and contained no voids or cracks. Size of SiO2 particles in the film was seen in the AFM analyses to increase with baking temperature. Sintering of SiO2 particles appeared to accelerate at temperatures over 450 °C.