The effect of surfactant removal on continuous mesoporous ultra-thin silica films-A study by X-ray reflectivity, X-ray diffraction and Kr adsorption

Supported triblock coplymer-SiO2 composite thin films of thickness ~ 0.2 µm were dip-coated on Si-wafer, glass and Au coated Si-wafer substrates. The copolymer template was found to be removed almost completely by UV-O3 irradiation and calcination as detected by grazing incident Fourier transform infrared spectroscopy. The porous SBA-15 continuous films of high porosity with large surface area and pore volume, low average density and thickness were produced through UV-O3 treatment as characterized by X-ray reflectivity (XRR) and Kr adsorption, and with low refractive index of 1.32 after hydrophobic modification. The water uptake was observed by XRR analysis inside both mesochannels and micropores in the mesochannel wall at high relative humidity (45-50%). The anisotropic shrinkage of films derived by template removal was detected by in-plane and out-of plane one dimensional X-ray diffraction and two dimensional grazing incident X-ray diffraction, which depending on the template removal methods, UV-O3 irradiation period and substrate employed.