Growth imperfections in three-dimensional colloidal self-assembly

Towards a full understanding of the growth dynamics and optical response of self-assembled photonic colloidal crystal films

“…These features have been repeatedly observed for a large number of samples, hence confirming the relation between film growth speed, crystal thickness and density of intrinsic defects in colloidal crystal films. Other groups have recently reported thorough analyses of the variations of crystal thickness along the growth direction 21,25 or of the relation between crystal thickness and defect density or domain size, 23,26 such observations being in fair agreement with those reported in ref. 18 and 19. A complete picture of the film growth process still lacks a description of the ordering of microspheres in a facecentred-cubic lattice within a receding meniscus.…”

Ultralow-n SiO2Thin Films Synthesized Using Organic Nanoparticles Template

“…Additionally, in all cases, as the concentration of the colloidal solution increases, the morphology of the template film seems to be improved because of the decrease in droplet surface tension, together with the increase in frictional force induced by a thicker wetting layer. 15 It is worth mentioning that the template film quality was enhanced by using PS-AA colloidal solutions instead of PS ones. This may be due to the fact that the water-soluble polyacrylic acid tails of the PS-AA made the colloidal solution more viscous and that the interaction between the particle-particle and particle-substrate were improved, where the frictional force and wetting surface tension were both increased, keeping a flat wetting layer from droplet formation.…”

“…During the drying process, water between the PS-10AA particles evaporated, producing a capillary force that in turn pulled particles closer together into a closely packed fashion. 15 Colloidal particles can be slipped over the substrate by capillary forces so that empty cracks are formed, as shown in Fig. 4d.…”

“…These values are close to that of ordered macroporous SiO 2 (74%) film fabricated from a closely packed colloidal template. 14,15 Since the sacrificial template films used for the synthesis of macroporous SiO 2 are less ordered, their high porosities here are likely to result in part from other resources. While in the first film, its porosity partially caused the removal of organic moieties during thermal treatment, the extremely high porosity of the second film was due to its hollow structure in which secondary voids exist among hollows.…”

“…This imperfect colloidal nanoparticle thin film is mainly due to a lack of controllability in process factors such as solvent (water in most cases) evaporation rate, which is required for maintaining the concentration of the colloidal solution and wetting ability of the colloidal solution upon the substrate surface. 15 In the case of PS, the low interaction between the particles and between the particle and substrate was attributed mainly to van der Waals interactions. In addition, the crystallization of PS particles is slow as growth of the template crystal driven by the capillary force is opposed by Brownian motion.…”