Spontaneous pattern formation on silica and titania dip-coating films prepared at extremely low substrate withdrawal speeds

Abstract

Linear patterns were spontaneously formed on the silica and titania dip-coating films prepared from tetramethyl orthosilicate (Si(OCH₃)₄) and titanium tetraisopropoxide (Ti(OC₃H₇ⁱ)₄) solutions, respectively. In both films, the pattern formation occurred at extremely low substrate withdrawal speeds below 1.0 cm min⁻¹, where the film thickness increased with decreasing substrate withdrawal speed for dip-coating. The linear patterns on micrometre scale were arranged perpendicular to the substrate withdrawal direction. The values of R_Z (10 point height of irregularities) and S (mean spacing of local peaks) of the patterns increased with decreasing substrate withdrawal speed.