Optical study on opaline thin films grown by vertical deposition

We have studied optical properties of opaline thin films grown by the vertical deposition method. The opaline films under study were three-dimensional close-packed arrangements of a-SiO 2 spheres. The fcc domains, which are of 10–50 μm in size and separated by cracks, were seen in FE-SEM images. Analysis of angle-resolved transmissivity of opaline films shows that they act as three-dimensional photonic crystals. Photonic stop-bands were observed and attributed to the {111} family of crystallographic planes. Crystallographic structure of the films was characterized as twinned fcc, in which twins are spatially separated by cracks.