| Photonic crystals (PC) are a kind of materials with periodic refractive indices. With the properties of photonic band and photonic localization, photonic crystals can control the propagation of light and have a promising application in many fields, such as optoelectronic integration, optical communication, and so on. At present, photonic crystals have been obtained in infrared and microwave region, but for UV-Vis. light range the study of theoretical and fabrication is relatively less. This is because most materials have high absorption coefficients, and tremendous trouble exists in the preparation of2D and3D PCs with several nanometers for present technology. However, for the simple structure and preparation of ID PCs, moreover, ID PCs can replace some higher dimensional PCs in applications, it is becoming hot point. The multilayer films can be regarded as ID PCs, composed of dielectric, semi-conductor or metal materials. Metal belongs to the dispersion medium and exist greater absorption due to the properties of negative refractivity in infrared to ultraviolet range. Therefore, it will be possible to make better optical properties. Titanium dioxide is a kind of semiconductor material in the visible region with high refraction, low-absorption, wide band gap, good chemical stability and photo-catalysis property. It is widely used in sensors, solar energy, catalysis and environmental governance, and so on. The research in the thesis was focused on the multilayer films based on TiO2. Based on the principle of transfer matrix method we designed multilayer ID PC with different structure, respectively using Cu, A12O3, SiO2. According to the designed models we fabricated the Cu/TiO2multilayer films. The detail of the study can be introduced as follows:1. We designed Cu/TiO2multilayer which photonic band gap (PBG) covered the range from640nm to1250nm, and the reflectivity was95%. The gap in TE and TM mode completely overlapped each other when the incident angle varied from0°to15°but incompletely overlapped each other when the incident angle more than15°, then the gaps became narrow in TE mode but broad in TM mode. Moreover, the reflectivity was62%in400nm, and the transmittance was0.2. Designed Al2O3/TiO2multilayer which PBG covered the UV-Vis. range from346nm to475nm, and the reflectivity was100%in400nm. With the increasing of the incident angle, the gaps move towards to short wavelength and became narrow in TE mode but broad in TM mode. Therefore, the gaps belong to the incomplete band gap.3. Designed (SiO2/TiO2/SiO2) multilayer ID PC which PBG covered the UV-Vis. range from320nm to400nm, and the transmittance was95.4%in400nm. After optimizing the structure, the gap became flat, and with the increasing of the incident angle, the gaps move towards to short wavelength and became broad. When the incident angle varied from0°to30°, the transmittance was100%in400nm. Thence, the structure is expected to be used for photocatalyst.4. By magnetron sputtering, we prepared Cu/TiO2multilayer films. The films were uniform, dense and amorphous. The transmittance and absorption of multilayer films is high than TiO2in400nm to800nm range. The structure can improve the utilization rate of the sunlight, in order to improve the photocatalysis efficiency. So the structure is hopeful to be used as the photocatalyst. |
