Fabrication of High Quality Three-Dimensional Photonic Crystals

High quality colloidal photonic crystals made from polystyrene spheres with diameter 240 nm are fabricated by the vertical deposition method. The scanning electron microscopy (SEM) and the transmittance spectrum are used to characterize the properties of the photonic crystal. The SEM images show that there are few lattice defects. The transmittance of the photonic crystal is above 75% in the pass band at 700 nm and is lower than 5% at the centre of the band gap, respectively. It is found that proper concentration is a very important factor to fabricate the photonic crystal when the diameter of the spheres is lower than 300 nm.