Ordering analysis of SiO2 particle-accumulated films by small-angle X-ray scattering

The ordered arrangement of particles and holes in SiO2 particle-accumulated films by small-angle X-ray scattering (SAXS) was investigated. The SAXS profiles of SiO2 particles exhibited the typical oscillation shown by monodisperse spherical particles. On the other hand, the SAXS profile of the ordered SiO2 particle-accumulated film showed an additional oscillation suggesting that another scattering component existed except for SiO2 particles. Furthermore, considering two components: “SiO2 in an air matrix” and “air holes in a SiO2 matrix”, we successfully reproduced the SAXS profile of the ordered particle-accumulated film. The additional oscillation shows the existence of the tetrahedral holes, suggesting that this SiO2 particle-accumulated film forms a close-packed structure. The intensity of the additional oscillation increased with the regularity of the particle arrangement in the SiO2 particle-accumulating film. These results suggest that SAXS measurements using synchrotron radiation can provide information on the order of particle arrangement in composite films.