Controlling the quality of SiO₂ colloidal crystals by temperature ramping on the vertical convective self-assembly method

Traditionally, the vertical convective self-assembly method (VCSA) uses time-invariant temperature conditions to obtain high-quality colloidal crystal (CC) films, leaving unexplored possible effects due to temperature variations during the elaboration process. Here, the quality of colloidal crystal films grown by the VCSA method when applying temperature ramps is investigated. This study is conducted by combining experimental measurements and simulations of concentration profile and meniscus displacement, using the temperature dependent Kynch’s theory. The quality of the elaborated CC films is evaluated by analyzing the resulting optical Bragg diffraction. Colloidal crystal films deposited under controlled parameters showed that high-quality films can be achieved by positioning the meniscus into the uniform zone under temperature ramping, as a definite relation between sedimentation velocity and evaporation rate, in agreement with modelling results.