Preparation of Polysilane/Silica Nano-particle Hybrid Thin Films and Their Optical Properties

Photofunctional polymethylphenylsilane (PMPS) and toluene dispersed silica nano-particles (13 nm average diameter) were used for the preparation of organic-inorganic hybrid thin films. The surface of silica nano-particles were modified with phenyl and methyl groups. The thin films were prepared by spin-coating the toluene solution of PMPS and silica nano-particles on quartz and silicon substrates, respectively. The UV spectra of polysilane/phenyl modified silica nano-particle hybrid thin films indicated a red-shift of absorption peak related to the Si-Si bond in PMPS. This interesting phenomenon was caused by the longer c-conjugation due to the stretched Si-Si bond, which was resulted from the pi-pi interaction of phenyl groups between PMPS and surface of silica nano-particles. Furthermore, after UV irradiation and heat treatment of the hybrid thin films containing small amount of PMPS, the cross-linked nano porous silica thin films with a low refractive index were obtained.