不同B/C摩尔比碳化硼薄膜的光学性能

Optical Properties of Boron Carbide Thin Films with Different B/C Molar Ratio

多层膜反射镜是X射线波段和极紫外波段的重要光学部件。碳化硼作为常见的反射膜材料,其薄膜成分及光学常数计算的准确性对反射镜的反射性能具有明显影响。本研究使用直流磁控溅射技术制备碳化硼薄膜,利用X射线光电子能谱(XPS)、X射线全反射(XRR)、原子力显微镜(AFM)和同步辐射光源等对试样进行了表征,利用改进的拟合函数拟合了基底和薄膜的反射率曲线。结果表明,非晶碳化硼薄膜的元素化学状态相同,其基本成分包含碳化硼和含氧碳化硼;在5~45 nm波段,薄膜B/C摩尔比为4.23时,反射性能最好,同时其基底与薄膜的电子密度差值最大,试样反射性能变化与试样电子密度差值变化基本一致;与原始拟合函数相比,改进的拟合函数提高了薄膜光学常数计算的准确性。

Multilayer mirrors are essential optical components in X-ray and extreme ultraviolet regions.As a common reflective coating material,the composition of boron carbide thin film and the accuracy of the optical constants calculation have great effect on the reflection performance of the mirror.Boron carbide thin films were grown with DC magnetron sputtering and characterized by XPS,XRR,AFM,synchrotron radiation,et al.The reflectance curves of the substrate and the film were fitted with the improved curve fitting function.Results show that amorphous boron carbide thin films consist of boron carbide and oxy-boron carbide,the chemical states of the elements are the same.Sample with B/C molar ratio of 4.23 shows the best reflection performance in the wavelength range from 5 nm to 45 nm,and it has the largest value of the electronic density difference between the substrate and the film.The change of the reflection property is basically the same as that of the electronic density diffe-rence of the samples.Compared with the original fitting function,the improved fitting function improves the accuracy of the optical constants calculation.