Growth of highly ordered colloidal photonic crystals using a modeling approach

Colloidal photonic crystals were grown using a vertical deposition method. The effect of colloidal concentration and deposition rate on crystalline quality and domain size was studied by means of response surface design. The crystalline quality was assessed using the optical reflectance. The results show that a strong negative correlation exists between the reflectance and the full width at half-maximum (FWHM), as illustrated by the close optimal region between maximizing reflectance and minimizing FWHM. For reflectance and FWHM, the quadratic effect of colloidal concentration is highly significant. For domain size, the colloidal concentration-lifting speed interaction effect was found to be significant. The observed colloidal concentration-lifting speed interaction effect explains the controversy that a low deposition rate is desirable at low colloidal concentrations, whereas a high deposition rate is favorable at high colloidal concentrations. Predictive models relating the important factors to the reflectance, FWHM, and domain size are proposed in the paper. The resulting optimal recipe shows a well-ordered structure with good optical reflectance, consistent with the prediction from modeling.