Defect healing of self-assembled SiO2 layer by heat-treatment and multi-coating.

This study examined the effect of heat-treatment and multi-coating on the microstructure and optical properties of photonic crystals (PCs) that had been self-assembled using mono-dispersed spherical SiO2 nanoparticles. When the heat-treatment temperature was increased, the reflectance peak due to the photonic bandgap moved to a shorter wavelength direction, and the peak intensity of the Fabry-Perot fringes increased. The highest reflectance peak intensity was obtained in the sample heat-treated at 250-300 degrees C. Heat-treatment reduced the average particle size and number of defects, and increased the packing density of the PC. When the heat-treatment temperatures were increased up to 900 degrees C, a large crack with an average size of approximately 1.3 microm was formed through the self-assembled layer. A multi-coating could effectively fill the open space of this crack and thereby reduce the total number of defects. The crystallinity and optical properties of the self-assembled PC were improved by the heat-treatment and multi-coating.