Self-assembly of SiO₂ colloidal crystals

SiO2 colloidal crystals were fabricated by vertical deposition and spin coating methods, and their appearance morphology, microstructure and photonic band-gap properties were compared. The used colloidal SiO2 spheres were synthesized by improved Stober method with different diameters and small relative standard deviation. With white light illumination, characteristic six-beam diffraction appears on the SiO2 colloidal crystal fabricated by spin coating, while stripes appear on the surface of the SiO2 colloidal crystal fabricated by vertical deposition. SEM images reveal that, with different dilutions in the same spin coating process conditions, the quality of SiO2 colloidal crystal dispersed in a mixture of glycol and ethanol is best. Transmission