Structural characteristics of oriented mesostructured silica thin films

Mesoporous thin films synthesized via an electrochemical strategy (ref 1) generally show granular domains, each of which is composed of hexagonally packed one-dimensional channels oriented uniquely perpendicular to the film surface. Grain boundaries either parallel or normal to the channel direction might affect the properties and subsequent application of the film. In this study, the structural details of oriented mesostructured silica thin films have been examined by transmission electron microscope. The pore structures are characterized using the traditional crystallographic concepts but show different structural properties from that of polycrystalline materials. The boundary structures vary much depending on the residual internal stress and the orientation relationship between the bounded grains. A variety of structural features, typically near the large-angle tilt boundaries, have been observed including coincidence site lattices, lattice distortion, lattice displacement, and dislocations. According to the present structural analysis, microstructure evolution and potential applications have been discussed with respect to the oriented mesoporous films.