Optical Properties of Boron Carbide Thin Films with Different B/C Molar Ratio
LI Qile1,2, YANG Yong1, WEI Yuquan1,2, LIU Meng1, ZHOU Hongjun3, HUO Tonglin3, HUANG Zhengren1
1 Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China
Abstract: 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.
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