Structural study of 3D-hexagonal mesoporous spin-coated sol-gel films

Mesostructured films deposited on glass substrates by spin coating are stud ied by X-ray diffraction, small angle X-ray scattering using grazing incide nce (GISAXS) and high resolution electron microscopy. The films generally p resent a gradient of ordering from the air/sol interface to the interior of the film, with a 3D-hexagonal mesophase near the surface and a disordered micellar structure at the interior. However, the 3D-hexagonal ordering and the texturing can be extended over all the film thickness by adjusting the composition of the deposited solution. In particular, critical values are c learly observed both for the size of silica units forming the walls in the mesophase and for the film thickness. All these results can be understood f rom the competition between structuration and gelation of the films during alcohol removal.