Application of the pressure controlled isothermal heating vertical deposition method to the fabrication of colloidal photonic crystals is systematically investigated in this paper. The fabricated samples are characterized by scanning electron microscope and transmission spectrum. High-quality samples with large transmissions in the pass bands and the sharp band edges are obtained and the optimum growth condition is determined. For the best sample, the transmission in the pass bands approaches 0.9 while that in the band gap reaches 0.1. More importantly, the maximum differential transmission as high as 0.1/nm is achieved. In addition, it is found that the number of stacking layers does not increase linearly with concentration of PS spheres in a solution, and a gradual saturation occurs when the concentration of PS spheres exceeds 1.5 wt.%. The uniformity of the fabricated samples is examined by transmission measurements on areas with different sizes. Finally, the tolerance of the fabricated samples to baking was studied.
Three-dimensional photonic crystal (PC) heterostructures with high quality are fabricated by using a pressure controlled isothermal heating vertical deposition technique. The formed heterostructures have higher quality, such as deeper band gaps and sharper band edges, than the heterostructures reported so far. Such a significant improvement in quality is due to the introduction of a thin TiO2 buffer layer between the two constitutional PCs. It is revealed that the disorder caused by lattice mismatch is successfully removed if the buffer layer is used once. As a result, the formed heterostructures possess the main features in the band gap of constitutional PCs. The crucial role of the thin buffer layer is also verified by numerical simulations based on the finite-difference time-domain technique.
