Preparation of antireflective SiO_2 nanometric films

摘要

Antireflective nanometric SiO_2 films were formed on glass substrates by dip coating from a colloidal SiO_2 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 SiO_2 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 A maximum light transmittance of 95% was obtained with 4.5% points increase, from the films which were withdrawn at 100 mm/min and baked at 450 or 500 °C. It was seen from SEM observations that the films exhibited full coverage on glass surface and contained no voids or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 SiO_2 particles in the film was seen in the AFM analyses to increase with baking temperature. Sintering of SiO_2 particles appeared to accelerate at temperatures over 450 °C.