Effect of modifiers on uniformity of spin-coated sol-gel silica antireflective films

The mechanism of radiative striations in spin-coated sol-gel silica antireflective films was analyzed. Several kinds of fluoroalkanol modified sols were prepared using the Stöber method in order to improve the surface properties of the spin-coated films, especially the surface roughness. Surface morphologies of the films were observed using the Nomarski optical microscope and AFM, and quantitatively evaluated by surface roughness measurement. Results show that the striation defects are eliminated, and the surface roughness(RMS) of the coatings reduces from 4.55 nm to 1.00 nm after modification, while the antireflective properties show no apparent change. The films' peak transmittance ranges from 99.60% to 99.89% with the laser damage threshold of 21.0 to 25.3 J/cm².