金刚石薄膜红外椭圆偏振参量的计算与拟合

用红外椭圆偏振仪对热丝化学气相沉积法制备的金刚石薄膜的光学参量进行了测量。由于表面状态和界面特性的差异，分别对镜面抛光硅片和粗糙氧化铝基片上的金刚石薄膜建立了不同的模型，并在此基础上进行了测试结果的计算拟合。为了综合反应诸如表面粗糙度等表面界面因素对测试结果的影响，根据衬底特性将表面层和界面层分离出来，并采用Bruggeman有效介质方法对它们的影响进行了近似处理。结果表明，硅衬底上金刚石薄膜的椭偏数据在模型引入了厚度为879nm的表面粗糙层之后能得到很好的拟合。而对于氧化铝衬底上的金刚石薄膜而言，除了在薄膜表面引入了粗糙层之外，还必须在衬底和金刚石界面处加入一层由体积分数为0．641的氧化铝、体积分数为0．2334的金刚石和体积分数为0．1253的空隙组成的复合过渡层(厚度995nm)，才能使计算值与实验参量很好地吻合。

Data Analysis of Optical Properties of Diamond Films by Infrared Spectroscopic Ellipsometry

Spectroscopic ellipsometric measurements in the infrared region is used to characterize the structure of CVD-diamond films. According to the status of surface and interface, different models are developed for diamond films on smooth silicon substrate and rough alumina substrate respectively with theoretical simulations followed. The Bruggeman effective media approximation, which includes the factors such as roughness, void and phase mixture, is applied to simulate the effects of rough surface and complicated interface on the ellipsometric data. It is found that the establishment of appropriate model has the strongest influence on the fit of ellipsometric spectra. The films on silicon substrates are well described by a two-layer film model. The bulk film (first layer) is pure diamond. The second layer (surface) represents a rough surface sublayer about (879 nm) thick, which contains 28.3% voids. But satisfactory agreements between experimental and calculated data cannot be obtained when the two-layer film model is applied to diamond films on alumina substrates. The best fit is achieved for the samples on alumina substrates with a (three-component) interface layer (64.13% alumina+23.34% diamond+12.53% void) included by Bruggeman effective media approximation.