Enhanced antireflection properties of silica thin films via redox deposition and hot-water treatment

Silicon oxide (SiOx) thin film was deposited onto poly(ethylene terephthalate) substrate by the reduction of an aqueous solution containing ammonium hexafluorosilicate, dimethylamine borane and cetyltrimethylammonium bromide (CTAB). Post-deposition hot water treatment: immersion of the film in water at 333 K dissolved CTAB producing nanopores in silica (SiO2) film and remarkably enhanced the antireflection property of the film: 0.1% at 550 nm of wavelength. The films before and after the treatment were compared via characterization by means of X-ray photoelectron spectroscopic depth profile, X-ray diffraction and transmission electron microscopy. The decrease of refractive index dispersion by the porous silica films, attributing to the low reflection, was verified by effective medium approximation analysis.