轻元素荧光分析用多层膜分光晶体的制备与表征

Fabrication and Characterization of Multilayer Analyzer Crystals for X-Ray Fluorescence Analysis on Light Elements

物质组分与结构分析是认知和研究物质的重要方式。利用X射线荧光光谱分析法可以对物质中的元素进行定性分析与定量检测,该方法是目前最为常规的物质组分和结构无损分析手段之一。在使用波长色散型X射线荧光光谱仪探测轻元素时,多层膜分光晶体是核心的光学元件。使用人工多层膜晶体代替普通晶体作分光晶体,可有效提升分析仪器对轻元素的检测能力。针对国产波长色散型X射线荧光光谱仪分析轻元素的实际需求,设计出了Mo/B4C,Cr/C,Cr/Sc,W/B4C(周期厚度d=3.63 nm)和W/B4C(周期厚度d=2.85 nm)多层膜分光晶体,分别适用于B,C,N,O,F五种轻元素的荧光探测。利用磁控溅射的方式,在尺寸为50 mm×30 mm的超光滑Si基底上完成了五种多层膜晶体的制备。采用高分辨率X射线衍射仪对各个多层膜晶体进行掠入射X射线反射测试,测试及拟合结果表明:五种多层膜晶体膜层结构规整、界面宽度小、成膜质量高,膜层均匀性好,整个镜面上周期厚度的均匀性误差均在1%以内。采用原子力显微镜表征了各个多层膜晶体的表面形貌,结果表明:五种多层膜晶体表面颗粒状结构尺寸较小,表面形貌平滑,表面粗糙度小。最后,通过模拟计算获得了各个多层膜晶体在掠入射工作角度下的反射率,分别为:Mo/B4C(30.1%@B-Kα线),Cr/C(29.3%@C-Kα线),Cr/Sc(35.4%@N-Kα线),W/B4C(d=3.63 nm,8.6%@O-Kα线),W/B4C(d=2.85 nm,10.7%@F-Kα线)。基于以上研究,所制备的五种多层膜分光晶体可以满足波长色散型X射线荧光光谱仪的需求,能够应用在B,C,N,O,F五种轻元素的探测中。

The composition and structure analysis is an important way to understand and study matters.X-ray fluorescence analysis(XRF)is one of the most universal nondestructive analysis methods for the composition and structure of substances,which can be used for qualitative analysis and quantitative detection of elements in substances.During the detection of light elements by wavelength dispersive X-ray fluorescence spectrometer,multilayer analyzer crystals are key optics.Using artificial multilayer crystals instead of natural crystals as analyzer crystals can effectively improve the ability of spectrometer to detect light elements.This paper,aiming at the actual application demands of domestic wavelength dispersive X-ray fluorescence spectrometer to analyze light elements,Mo/B_4C,Cr/C,Cr/Sc,W/B_4C(period thickness d=3.63 nm)and W/B_4C(period thickness d=2.85 nm)multilayer analyzer crystals are designed,which are suitable for the fluorescence analysis of light elements B,C,N,O,and F,respectively.Five kinds of multilayer crystals have been fabricated using the direct-current(DC)magnetron sputtering technique on super-polished silicon substrates with the size of 50 mm×30 mm by magnetron sputtering.Interfacial microstructures of as-deposited multilayer crystals were characterized by grazing incidence X-ray reflectometry(GIXR)on a high-resolution X-ray diffractometer.The measured results indicate that all five kinds of multilayer crystals have high-quality periodic layer structures and smooth interfaces,and the thickness deviation of period thickness for the five multilayer crystals is less than 1%.Atomic force microscopy(AFM)was used to characterize the surface morphology of each multilayer crystal.The results reveal that all five multilayer crystals have smooth surface morphology and small surface roughness.Finally,the reflectivity of the five crystals at grazing incidence geometry was obtained by simulation:Mo/B_4C(30.1%@B-Kαline),Cr/C(29.3%@C-Kαline),Cr/Sc(35.4%@N-Kαline),W/B_4C(d=3.63 nm,8.6%@O-Kαline),W/B_4C(d=2.85 nm,10.7%@F-Kαline).Based on these investigations,the five kinds of multilayer analyzer crystals meet the practical application requirements of wavelength dispersive X-ray fluorescence spectrometer.They can be applied to detect light elements B,C,N,O,F.