溶胶—凝胶法制备TiO₂/SiO₂宽带增透膜及偏振分光膜研究

【作者】 王永强；

【导师】 胡晓云；

【作者基本信息】 西北大学 ， 凝聚态物理， 2008， 硕士

【摘要】 本文首先利用Mass膜系设计软件，根据多层膜理论，对由TiO₂和SiO₂两种材料组成的交替多层膜进行理论模拟设计，得到最佳化和最优化的宽带增透膜模型和偏振分光膜模型。然后以理论模拟结果为指导，利用溶胶-凝胶技术，在酸催化体系中以钛酸丁酯（Ti（OBu）₄）为前驱体制得TiO₂溶胶，以正硅酸乙酯（TEOS）为前驱体制得SiO₂溶胶，采用提拉法在普通载玻片上分别镀制不同膜层结构的宽带增透膜和偏振分光膜。利用双光束紫外-可见分光光度计、原子力显微镜、拉曼光谱仪、椭圆偏振仪、双通道光率计等仪器对样品进行表征，研究了样品的透射光谱及透射比、表面形貌、膜层厚度、消光比等特性。增透膜的模拟计算结果表明，垂直入射时，双面镀TiO₂／SiO₂膜（hl膜），在整个440-700nm波段，光线的透射比为99％左右，其增透效果要好于单面膜。根据理论模拟结果，实验采用“交替镀膜”法，制备出宽带增透TiO₂／SiO₂多层膜，其方法有别于以往的TiO₂+SiO₂”复合膜”法。实验发现，双面hl膜具有明显的宽带增透效果：在400-700nm波段，当光线垂直入射时，增透7％左右；45°角入射时，可增透10％。研究了提拉速度和退火温度对样品透射比的影响，结果表明，提拉速度为9cm／min，膜厚大约为255nm时，整个波段透射效果最好；退火处理对膜片的透射比影响较大，控制退火温度及提拉速度，可以使某些波段透射比增强。薄膜表面的AFM图表明hl膜的表面均匀性良好，80℃处理后薄膜膜层的均方根表面粗糙度（RMS）为1．682，平均粗糙度（RA）为1．208；300℃退火后，其RMS为0．289，RA仅为0．207；550℃退火后，其RMS为0．167，RA仅为0．108。随着退火温度升高，表面粗糙度降低，而表面粗糙度大的薄膜其透射效果较好，这主要是由于随退火温度升高-OH被除去的缘故。偏振分光膜的模拟计算结果表明，TiO₂／SiO₂四层膜（lhlh膜），在400-700nm比较宽的波带范围内，其透射比和反射比接近50％，能够很好地实现分光；其S光反射比可以达到95％，P光的透射比在90％左右，能够较好地分开S光和P光。在实验室中，利用溶胶-凝胶技术，采用提拉法镀制了此种薄膜，对样品的偏振特性及消光比等做了测量。实验测试结果如下：透射P光在检偏器的转动360°的情况下，其曲线变化遵循马吕斯定律，且相对于最大光强，最小光强基本为0；两光强峰值对称，这说明样品棱镜的起偏振性能良好。样品的消光比为476：1。在400-700nm比较宽的波段范围内，样品的P光的透射比超过80％，且其消光比随入射角的变化不敏感。更多还原

【Abstract】 In virtue of the thin film designing software Mass, broadband reflection reducing coating and polarizing beam splitter composed of TiO₂/SiO₂ multilayer films have been prepared according with the multilayer theory. Titanic oxide sol and silicon dioxide sol were obtained by hydrolysis and co-condensation reactions occurred in acid-catalyzed system by carefully controlling the sol-gel process of tetrabutylorthotitanate （Ti（OBu）₄） and tetraethoxysilane （TEOS）. The samples were coated on glass slides by dipping method. The samples’ characters, such as transmission spectrum, surface morphologies, thickness and extinction ratio were studied by double-beam ultraviolet-visible spectrophotometer, atomic force microscopy （AFM）, ellipsometer and dual-channel power meter.The result of simulation shows that the transmission spectrum of the TiO₂/SiO₂ films for both surfaces is 99% at normal incidence. It’s better than the films for one suface. Using the alternating coated method differing from the composite method, the broadband reflection reducing coating was prepared. The result of experimentation: from the transmission spectra of the samples we can see that for the case of vertical incidence, the average transmission of the slide sample increased 7% compared to the uncoated one in the spectra range from 400nm to 700nm, for 45°incidence the increase is 10%. The dependence of samples’ transmittance on hoist speed and annealing temperature was investigated. It is best when hoist speed is 9cm/min and the film thickness is 255nm. Annealing treatment had great effect on transmittance. Through controlling annealing temperature and hoist speed, the transmittance at some wave band can be enhanced. The reflection reducing coating of 80℃annealed has smooth and even surface, its Root Mean Square （RMS） and Average Roughness （RA） are estimated to be 1.682 and 1.208 . To the film of 300℃annealed the RMS and RA are estimated to be 0.289 and 0.207 and to the film of 500℃annealed they are 0.167 and 0.108. The surface roughness decreasd with increasing of the annealing temperature and the transmission is high when the surface roughness is big, because the hydroxy was removed with increasing of temperature.Broadband polarizing beam splitters were designed. The transmittance and reflectivity of TiO₂/SiO₂ four-layer alternate films is approaching 50% in range from 430nm to 700nm. The reflectance of the S polarized light is 95% and the transmittance of the P polarized light is 90%, so the S polarized light and P polarized light were better detached. In the lab, the samples were prepared using sol-gel technology by dip-coating and the testing methods were designed. The results show that the transmittance of the P polarized light obeys the Malus law with the turning of analyzer, further more the minimum approach zero compare with maximum and the wave crests of transmitted light were symmetric. Those show that the polarize of the samples are batter. The extinction ratio of sample is 476:1. The transmittance of P polarized light is extend to more than 80% in the spectra range from 400nm to 700nm,and its extinction ratio is insensitive to the change of incident angle.更多还原