MgF <2> / TiO 2 Double-layer Antireflective Films

Based on the TFC film system design software, in the range380~780nm visibleband, the MgF2/TiO2antireflection coating system has been desigened, and theencapsulate materials refractive index has been considered. The thin films have beendeposited by electron beam evaporation. The film system has been optimized. First,many experiments have been done for the technology parameters of deposting MgF2and TiO2thin film. The SEM, ellipsometry, XRD, UV-visible absorption/reflectionspectra have been used for analyzesed the performences of thin films. By experiments,the following resultes have been obiained:1.For TiO2film, the film thickness gradually increase, with increasing depositingtime, and the compactness of the film increase, and the film surface becomes smooth.The refractive index of the film change between2.0to2.25;2. For TiO2film, with the substrate temperature increases, the surface of the filmbecomes smooth;and the refractive index of the film increase;3. For TiO2film, with deporsiting pressure from1.0×10-3pa to5.0×10-3pa, thecompactness of the film increase, and the surface of the film becomes smooth, butwith deporsting pressure from5.0×10-3pa to9.0×10-3pa,the surface of the filmbecomes rough. The optimum deporsting pressure is5.0×10-3pa, and the filmrefractive index is2.3, the amorphous TiO2films have been obiained;4. The450℃are the crystallization temperature of TiO2films. That is to say theamorphous TiO2film changes to crystalline TiO2thin films;5. For MgF2film, the film thickness increase with the depositing time increases, andthe compactness of the film increases, and the film surface becomes smooth; and therefractive index of the film changes between1.373to1.384;6. For MgF2film, the film thickness increase with the substrate temperatureincreases, and the compactness of the film increases, and surface of the the filmbecomes smooth;7. For MgF2/TiO2double-layer film system, at a wavelength of500~600nm and800~1200nm, the low reflectivity of double antireflection system has been obtained.