Structure and Optical Properties of Opal Films Made by an Out-of-Plane Electric Field-Assisted Capillary Deposition Method

Self-assembled opals that are considered as a promising candidate for three-dimensional photonic crystals often suffer from the existence of internal defects. Defects influence optical properties and limit the applicability of opal films. Directed assembly using external fields may offer a certain degree of tunability in the opal formation process. We investigate the effect of an out-of-plane electric field on the formation and optical properties of opal films deposited using the capillary deposition method. The application of an electric field of intermediate strength (20–30 V/cm) can improve opal quality. The quality of opal films was found to depend on the polarity of the bottom substrate resulting from the beneficial influence of an asymmetry between the growths and the interplay with gravity. The negatively charged bottom substrate results in slightly better opal quality. This finding shows the potential of electric fields to tune opal formation in order to reduce the defect content