Large-scale self-organized growth of (001) surface-oriented colloidal crystals by edge meniscus effect

Millimeter-sized films of (100) facing face-centered crystals (fcc) of colloidal nanoparticles have been fabricated by self-assembly on silicon substrates and studied by both optical and scanning electron microscopy. The top surface layer sometimes also reconstructs to form a 1 x n (n varies from 2-7) superstructure. Such (100) oriented regions of the colloidal film are apt to concentrate near the edge of the substrate, and changing the width of the substrate could control the areas of the (100)-oriented domains. The formation of the square packing surface pattern is related to the shape of the meniscus at the edges of the substrate, where the particles suffer additional shear force and higher evaporation, which can be used to control the location and size of the square arrangement of nanoparticles.