Ⅰ.Photo-induced Characteristics Of The Nanoscale TiO₂ Thin Films Prepared By RF Sputtering Ⅱ.Study On One-dimensional Photonic Crystals With The Nonlinear Defect Layers

I. Photo-induced Characteristics of the Nanoscale Titanium Dioxide Thin Films Prepared by RF SputteringNanoscale TiO2 thin films were prepared by RF magnetron sputtering process. TiO2-SiO2 and M-TiO2 composite thin films were prepared by RF magnetron co-sputtering process. Their photocatalytic activity and photo-induced hydrophilicity were investigated. This work includes three parts.1) Nanoscale titanium dioxide thin films were prepared at room temperature by RF magnetron sputtering process. Microstructure of thin films with different sputtering pressures and different annealed temperatures was measured by XRD, AFM and Raman spectra, and their photo-induced hydrophilicity and photocatalytic activity have been studied. It shows that the as-prepared TiO2 thin films are in amorphous state and the anatase phase forms when anneal temperature is over 400℃. The TiO₂ thin films annealed at 400℃ for an hour exhibit a good hydrophilicity and photocatalytic activity.Electrochemical characteristic of ITO/TiO2 electrode under UV irradiation was investigated using the method of cyclic voltammetry. There are two photoelectrochemical processes for TiO2 electrode under UV Illumination. One is a fast process, which resulted on the appearance of anodic photocurrent. The other is a slow process, which will be responsible for the formation of Ti3+ on the surface when the TiO2 thin films were irradiated by UV light. Photo-generated currents were observed under 254nm and 365nm UV irradiation. New oxidative peaks were observed when the TiO2 electrode was irradiated by 254 nm UV light for a certain time. The peak current increased with the increase of UV irradiation time. It is assumed that the new oxidative peak belonging to the oxidation of Ti3+, which was formed during the UV illumination, and the changes of hydrophilicity of the films may be related with the formation of Ti3+ on the surface when the films were irradiated by UV light.2) SiO2/TiO2 composite thin films were prepared by RF magnetron co-sputtering process. The ratio of SiO2 to TiO2 can be adjusted by controlling the sputtering time of SiO2 and TiO2 targets, respectively. All SiO2/TiO2 composite thin films annealed at 400℃ for an hour have the anatase phase. The refractive index of SiO2/TiO2 composite thin films decreases with the ratio of SiO2 increases. It is found that adding SiO2 will reduce the photocatalytic activity of SiO2/TiO2 composite thin films but improve its maintaining timeof super-hydrophilicity. The contact angle of SiCVTiC^ composite thin films with SiC>2 ratio of 6-13% decreases to 2° after 30 minutes under UV irradiation, and keeps lower than 6° for 5 days without UV irradiation.3) M-TiC>2 (M=Au/Ag/Cu) thin films were prepared by RF magnetron co-sputtering process. The ratio of metal to TiCh can be adjusted by controlling sputtering time of metal target. The M-TiO2 thin films annealed at 400'C for an hour were anatase phase. Photocatalytic degradation of methylene blue (MB) dye in aqueous solutions by M-TiO2 thin films was carried under UV irradiation. Electrochemical characteristics of M-TiCh/ITO electrodes under UV irradiation were investigated using the method of cyclic voltammetry. Experimental results show that an optimal Ag content of 1.5% of the Ag-TiC>2 thin films enhanced the MB photodegradation and the photo-induced current. The enhancement of photocatalytic activity is attributed to the suppressing of recombination of excited electron-hole pairs. The photocatalytic activity of Au-TiO2 thin films decreased slightly and Cu-TiCh thin films have a poor photocatalytic activity.EL. Study on One-dimensional Photonic Crystals with the Nonlinear Defect LayersOne-dimensional photonic crystals (ID PC) with CdS defect layers were calculated by transfer matrix method and fabricated by vacuum deposition process. Two-photon-absorption (TPA) were investigated by pump-probe measurement. This work includes four parts:1) Localized electric field intensity in defect layers of one-dimensional photonic crystals was investigated by transfer matrix method. Effect of defect material, defect mode, period and band gap on localized electric field intensity was discussed, respectively. Simulation results show that the maximum of electric field intensity in defect layers is obtained for normal incidence, quarter-wavelength of high and low refractive index dielectric layer and matched defect mode. The electric field intensity increases with the period increase and decreases for absorption of defect material. The defect mode can be adjusted by changing the thickness of defect laye.2) One-dimensional photonic crystals with a CdS defect layer of different structural parameters (defect mode, period and photonic band gap) were fabricated by vacuum deposition process and TPA coefficients were investigated by pump-probe measurement. The TPA coefficients were influenced by the structural parameters of ID PC and increased with the period increase and the distance decrease between the defect mode and midgap of photonic band gap. The best TPA coefficient was 164.0 cm/GW and was 28 times...