Fabrication and Characterization of Colloidal Photonic Crystals Self-assembled by Monodispersed Silica Nanospheres

The monodisperse silica spheres with diameters of 200-350 nm were synthesized by hydrolysis of tetraethyl orthosilicate based on the Stober process, and silica colloidal crystals was fabricated with a vertical deposition self-assembly method. Scanning electron microscopy and optical transmission spectra were applied to characterize the structures and properties of the deposited films. Experimental results show that the silica spheres form a face-centered cubic structure and the film thickness can be manipulated by controlling the particle concentration. The distinct peaks of transmission spectra for colloidal layers depend on the size of the silica spheres, which are consistent with theoretical calculation according to Bragg’s law. The depth of the optical stop band can be tuned by varying the volume fraction of SiO2 particles in the colloidal suspension.