High-reflection optical thin films based on SiO2/TiO2 nanoparticles multilayers by dip coating

The alternately stacking layers of SiO2 and TiO2 nanoparticles with different refractive indices were fabricated to form the distributed Bragg reflectors on the silicon wafer by dip coating method. By appropriate design of the thickness of the quarter-wave layers, the peak reflectance region can be tuned from the blue-green to the infrared portion of the electromagnetic spectrum. The peak reflectance of 65% at 800 nm and at 1600 nm has been achieved using seven periods, respectively; meanwhile, compared with the simulation, 80% at 800 nm and 70% at 1620 nm for seven periods, respectively. The scanning electron microscopy and the atomic force microscope studies confirm the thickness uniformity achieved along the fabrication direction, and a good quality of surfaces and interfaces.