Phtonic crystal is promising systems for application in the fields of optoelectronics and optical communication. Many researchers currently employ the same lithographic chip-patterning techniques used in advanced elctronics to make photonic crystals. But lithography has a difficulty in making thick 3D photonic crystals, which are needed for optoelectronic devices. Therefore in this research 3D photonic crystals(colloidal crystals) of monodispersed spherical $SiO_2$ were fabricated by using the self-assembly method.
Monodispersed spherical $SiO_2$ particles with various size were synthesized with $TEOS-EtOH-H_2O-NH_4OH$ system and $MTMS-H_2O-NH_4OH$ system by hydrolysis and condensation reactions. The particle size and size distribution were controlled by changing the amount of TEOS and MTMS, the volume ratio of $H_2O$ to EtOH, and reaction temperature.
Colloidal photonic crystals ordered in the area of about 1 ㎠, were self-assembled by using vertical-substrate-solvent-evaporation method. The number of ordered $SiO_2$ layers could be controlled by changing the amount of dispersed $SiO_2$ volume fraction in the solvent. The optical properties of 3D photonic crystals were observed with different $SiO_2$ size and number of layers. The positions $(\lambda_{Bragg})$ of the first-order Bragg diffraction peak increased as the self-assembled $SiO_2$ size increased. And the intensity of Bragg diffraction peaks increased as the thickness of self-assembles $SiO_2$ increased.
Patterned $SiO_2$ photonic crystals were fabricated on the patterned PDMS, whose width and height were 50 μm and 30 μm and patterned glass with PR, whose width and height were 10 μm by using solvent-evaporation-with-ultrasonic method. And patterned $SiO_2$ photonic crystals were fabricated on patterned glass with PR whose width and height were 10 μm and 1.4 μm, respectively by using vertical-substrate-solvent-evaporation method.
