Kojiro Okude

Photoluminescence behavior of SiO2 prepared by sol–gel processing

Two kinds of SiO2 were prepared by the usual sol–gel process (heat-treated sample) or a sol–gel process using photoirradiation (photoirradiated sample) and their photoluminescence behaviors were investigated. All heat-treated samples had photoluminescence bands, but none of the photoirradiated samples did. Intensity of emission of heat-treated sample increased as the treatment temperature increased. This photoluminescence behavior occurred reversibly with thermal treatment and photoirradiation. The network structure of SiO2 samples were evaluated by solid state NMR. The intensity of 17O solid state NMR peak increased with increased emission intensity. These results implied that heat-treated samples included some defects which showed photosensitivity, but the photoirradiated samples lacked such defects and formed a rigid network structure instead. These defects caused the observed photoluminescence.

Synthesis of SiO2 thin films by sol-gel method using photoirradiation and molecular structure analysis - Code: EP1

The SiO2 thin films were prepared by a process which combines a sol-gel method and photoirradiation. The HF etch rate and microhardness of a film prepared by this process were better than those of a film furnace-fired at same temperature. The Raman and 29Si solid state NMR spectra of film prepared by this process were similar to those of a film furnace-fired at higher temperature. There are many unstable folded non-linear SiO2 species in the film prepared at low temperature. On treatment at higher temperature, unstable folded non-linear Si-O-Si rearranges to the stable linear Si-O-Si bond. Photoirradiation enhances this structure change. The process provided denser and harder SiO2 thin films, even at low temperature, than the conventional furnace-firing method did.