Surface-modulation-controlled three-dimensional colloidal crystals

Significant effects of the modulation depth (h) on a three-dimensional (3D) colloidal self-assembly with symmetric and asymmetric two-dimensional (2D) templates are demonstrated. When the ratio “h/D” of the surface modulation (h) to the diameter of the bead (D) exceeded 0.35, then 3D square array patterns were obtained, and when the ratio h/D was from 0.28 to 0.35, pseudo-{110} structure resulted. When the ratio h/D was less than 0.28, the 3D crystallization of colloids was not observed but regular tetragonal or hexagonal clusters were formed in a 2D pattern.