Characterization of two-dimensional colloidal polycrystalline materials using optical diffraction

We present an optical-diffraction method for quantitative characterization of two-dimensional colloidal polycrystalline materials. From the angular-diffraction profile we can estimate both the average size of the crystalline grain and the defect density within the grains. Our statistical diffraction model shows that the diffraction line shape is close to a Lorentzian profile if a lot of defects exist within a grain, and it becomes close to Gaussian if the grains are essentially free of defects. This method is used for analyzing the quality of polystyrene colloidal crystals produced by the evaporation technique. The results are compared with direct statistical analysis of microscope images.