Time-resolved in-situ x-ray diffraction study of the formation of 3D-hexagonal mesoporous silica films

Highly oriented 3D-hexagonal silica thin films have been produced on silicon substrates by dip-coating technique, using cetyltrimethylammonium (CTAB) bromide as structuring agent. For the first time, time-resolved in situ X-ray diffraction experiments have been used to investigate the formation of such mesostructured films. Interestingly, the data shows that an intermediate mesophase appears just after film deposition (t<500 ms), characterized by one diffraction peak centered at a d spacing of 65 Å. Then after 20 s, another mesophase appears with a shorter d spacing (44 Å), which corresponds to the 3D-hexagonal structure found for the final dried film.