Self-Assembly of Crack-Free Silica Colloidal Crystals on Patterned Silicon Substrates

Face-centered cubic (fcc) (111)-orientated two-dimensional (2D) and three-dimensional (3D) crack-free silica colloidal crystals (CCs) were fabricated on patterned silicon substrates via a vertical deposition method. The influence of the surface properties of the substrate and the concentration of colloidal microspheres on the self-assembly were studied. The results showed that monolayer of silica microspheres self-assembled on a hydrophobic substrate surface while on a hydrophilic surface multilayer of silica microspheres formed under otherwise the same experimental conditions. The number of CC layers grown on the patterned substrate was proportional to the volume fraction of the colloidal microspheres. The optical properties of the samples were less influenced by the patterned surface with increasing the volume fraction of the colloidal suspension when the patterned substrates were fully covered by the CCs. The results presented in this paper reveal that the vertical deposition method can allow the formation of crack-free and well-ordered 3D CCs in large domains on patterned surfaces.