Pyramid-shaped assembly of colloidal particles underneath top-gathering pillars

Pyramidal assemblies of polystyrene (PS) or SiO2 particles were fabricated by micromolding underneath top-gathering pillar arrays, and their optical properties were investigated. The assembly was milled by a focused ion beam and the inner side was observed by SEM. The transmittance and reflectance spectra of the assemblies composed of PS particles with diameters of 212 nm and 300 nm showed a dip and a peak, respectively, which corresponded to a Bragg reflection maximum for (1 1 1) of the face-centered cubic lattice structure or (0 0 0 1) of the hexagonal close-packed lattice structure. These results revealed that the particles were densely packed partially on the top and underneath the top-gathering pillars and that the packing of the particles would occur from the top of the top-gathering pillars.