Thermal Annealing of SiO ₂ Fabricated by Flame Hydrolysis Deposition

Amorphous SiO 2 films were fabricated on Si substrates by flame hydrolysis deposition as buffer layers applied in the planar optical waveguides. Then the Si wafers with the porous particles were put into electric furnace annealing at different temperatures for consolidation in air. The products were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, and variable angle spectroscopic ellipsometry. It was found that different structures at different annealing temperatures were obtained. When the annealing temperature arrives at 1400°C, SiO 2 is continuous and dense and the refractive index at 1550 nm is 1.4564, which is highly desirable.