Large-area colloidal crystals are produced by the shear-alignment of stabilized PMMA. Domain areas of several square centimeters are formed. The shear influences the stacking sequence of the hexagonally close-packed layers of spheres. Two face-centred cubic (fcc) structures are produced, one for each shearing direction. On cessation of the shear the stacking relaxes to faulted twinned fcc. Pure fcc structures are fabricated by applying shear sequentially in three directions. We are able to make permanent fcc crystals by dispersing spheres directly in an epoxy resin host. After shear was applied the colloidal crystal was exposed to UV light, thus solidifying the crystal. This technique creates larger crystal domains compared to standard sedimentation techniques that have a low defect density and show excellent optical quality.
Figure1. Scanning electron microscope images of the solidified colloidal crystal film. Long range face-centred cubic packing is observed.