Process optimization of sedimentation self-assembly of opal photonic crystals under relative humidity-controlled environments

Minimum time of fabricating high quality of opal photonic band gap (PBG) crystal films was obtained by adjusting the relative humidity (RH)-controlled environments using the process optimization approach developed in this study. A three-stage process of silica particle (380 nm) deposition was proposed for the PBG crystal fabrication. The stop band intensity of the produced PBG film was determined using a spectrometer to represent the quality of the film. A process model of the film quality associated with the RH environments at the three stages was constructed using a design of experiment (DOE) and an artificial neural networks (ANN) methods. Results show that the quality of the PBG films was most influenced by the RH environment in the final deposition stage. The optimization approach with the built ANN model was used to estimate the optimal RH-controlled conditions to minimize the fabrication time of required PBG films. Moreover, the predicted optimal operating conditions were verified by experimental tests which results agree with the estimated quality of the PBG films.