Formation of Silica Coatings from Perhydropolysilazane Using Vacuum Ultraviolet Excimer Lamp

Silica coatings have been prepared by the spin-coating technique with the 172 nm vacuum ultraviolet (VUV) irradiation using a Xe2∗ excimer lamp. Perhydropolysilazane was used as a precursor. The chemical states, composition and optical transmittance of VUV-irradiated films were investigated by Fourier transform infrared, X-ray photoelectron, UV-visible absorption spectroscopies. The results showed that VUV irradiation was effective to remove hydrogen and nitrogen from the coating film and to incorporate oxygen to the film, so that the film transforms into silica. The effects of VUV treatment on the film were found to be dependent on oxygen concentration in surrounding gas. It was suggested that the effect of oxidation reaction due to active oxygen species and/or ozone is larger than that of the cleavage of a chemical bonding by photon energy.