Capillary focused microbeam X-ray diffractometer and its application
(Key Laboratory of ray beam technology, Ministry of education, School of nuclear science and technology, Beijing Normal University https://img.yqqlm.com/index/index/getInterUrl?uicrIvZQ=83958802ebe91f8c96636581c6338ff35)
With the continuous progress of natural science, many fields are developing towards the micro level, and people’s analysis of matter goes deep into the micro area. Microbeam X-ray diffraction analysis technology is a useful tool for nondestructive analysis of micro samples or sample micro region phase structure. It has been applied in many fields with the characteristics of nondestructive, micro region and high spatial resolution. Combining capillary x-ray focusing technology with X-ray diffraction analysis technology, our laboratory has designed and developed a new capillary focused microbeam X-ray diffractometer. It makes use of the characteristics of capillary X-ray lens to converge the X-ray beam emitted by the X-ray source to the micron level, so as to realize the phase analysis of small samples or sample micro areas, and provide a solution for the nondestructive micro area phase analysis of metal cultural relics and ceramic cultural relics.
Micro X-ray diffraction (µ -xrd) is a reliable and nondestructive phase structure analysis technology, which has been widely used in biochemistry, material science, geoscience, stress analysis and other fields[1-6]。 At present, there are two main methods to obtain the incident X-ray of microbeam:collimator beam limiting and X-ray optical focusing. It is the first method used in the microbeam X-ray diffractometer to obtain the microbeam incident X-ray through the collimator beam limiting. Specifically, the collimating slit or small hole is used as an aperture on the incident light path to reduce the divergence of the incident X-ray. However, at the same time, the intensity of the incident beam will be reduced due to physical obstruction, resulting in the weak diffraction information, which is difficult to achieve the ideal analysis effect[three,4]。 Based on the principle of X-ray total reflection, the multi capillary X-ray lens can converge the X-rays with multiple total reflections on the inner surface of the hollow capillary at one focal point. Therefore, the X-rays generated from the X-ray source can be collected at a large angle, and the beam spot size of the converged X-rays can be as low as tens of microns. At the same time, the capillary X-ray lens α The energy has a magnification of up to two-three orders of magnitude[seven], and has low divergence, which is very suitable for non-destructive analysis of micro samples and micro region phase structure of samples.
At present, the Deight series X-ray diffractometer produced by Bruker company in Germany is realized by adding an additional module integrated by micro focus X-ray source and multi capillary X-ray lens μ- Functions of XRD analysis[eight]； Italian Landis laboratory has developed an integrated multi capillary half lens μ- XRD diffraction[9,10]Instrument. However, due to the lack of two-dimensional and three-dimensional automatic control platforms, it is difficult to achieve the accurate positioning of the sample micro measurement points, let alone the two-dimensional measurement of the sample micro area μ- XRD analysis. For the needs of micro samples and micro region µ -xrd analysis, our laboratory designed and developed a new micro beam X-ray diffractometer and the corresponding computer control program, and carried out the research on the related analysis methodology.
The appearance of the capillary focused microbeam X-ray diffractometer designed by our laboratory is shown in Figure 1. It mainly consists of a micro focal spot x-ray tube (Cu target, focal spot size 50 μ m × fifty μ m) Capillary X-ray lens (cu-k α Beam spot size at energy is 100 µ m), receiving slit, SDD X-ray detector (energy resolution is 145ev at 5.9kev, effective area of beryllium window is two5 mmtwo）、具有two0倍放大功能的1400万像素固定焦距CCD摄像头、测角仪，XYZφ四维样品台，以及在LabVIEW语言环境下开发的仪器控制程序等部分组成。
Fig. 1 appearance of microbeam X-ray diffractometer
控制程序的主界面具有微区X射线衍射分析和微区能量色散X射线荧光（micro energy dispersive X-ray fluorescence，μ-EDXRF）分析两种模式，如图two所示。谱图显示区域在探测过程中实时显示X射线探测器探测到的谱图。此外，该仪器使用的高精度自动化三维运动平台可以满足微区的二维μ-XRD分析的需求，以便实现对感兴趣区域内物相分布的分析等相关问题。
图two 微束X射线衍射仪控制程序的主界面与Si (4 0 0)的X射线衍射图
three.1 analysis of titanium nitride film
The film has strong performance, but it will also fail due to various internal or external factors. Therefore, the change of the microscopic characteristics of thin films plays an important role in the study of the macroscopic characteristics. In this paper, tin thin films are selected as the research object, in order to understand the preferred orientation of tin crystal growth in the thin films and quickly evaluate it. The tin thin film is first implanted by metal vacuum vapor arc ion source (MEVVA) and then deposited by magnetic filtered vacuum cathode arc deposition system (FCVA). The tested sample is shown in Figure three. Part a and part B are tin films, and part C is three04 stainless steel substrate. Part a is closer to the edge of the whole sample, and the region of interest is marked in the middle rectangular frame (0.5 mm × 5.0 mm）。 Because the shape of each part in the figure is irregular, it is easy to be covered by the ray beam of the conventional X-ray instrument without difference, so it is necessary to carry out microanalysis here.
Fig. three tin film, three04 stainless steel substrate and tested position
在μ-EDXRF分析模式下，X射线管电压为three0 kV，管电流为0.5 mA，X射线束与样品表面的夹角θ1和X射线探测器铍窗的中心线与样品表面的夹角θtwo均为45°，探测器探测活时间为60 s，测量得到的μ-EDXRF光谱见图4。同时，选择如图three中所示的感兴趣区域，使用微束X射线衍射仪进行µ-EDXRF二维扫描分析。扫描步距为50 μm，每个点的测量条件与μ-EDXRF分析保持一致，每步的探测活时间为500 ms。经过数据处理，得到扫描区域内各元素的分布如图5所示。在µ-XRD分析模式下，X射线管的设置与µ-EDXRF分析模式下相同，测角仪twoθ范围为10°~1two0°，步距角为0.1°，每步的探测活时间为1 s，测量得到的X射线衍射图谱如图6所示。
Fig. 4 measurement points of tin film μ- EDXRF spectrum
Fig. 5 distribution of Fe and Ti elements in scanning area of tin film
Fig. 6 measurement points of tin film μ- XRD pattern
It can be seen from Figure 4 that the main fluorescence peaks of tin film measurement points a and B come from Ti element. Meanwhile, the measured main alloy elements of three04 stainless steel substrate are Fe, Ni and Cr. According to the intensity of the fluorescence peak, the relative content of Fe and CR at point a is higher than that at point B, while the relative content of Ti at point B is higher than that at point a, that is, more ti is deposited at point B. It can be seen from Figure 5 that the content of Ti has changed significantly from the middle to the edge, which is mainly affected by the coverage area of the deposition beam on the three04 stainless steel substrate, and the change of this content is related to the change of the film phase.
图6的测量结果表明，在该TiN薄膜中TiN所呈现的取向分别为（1 1 1）、（two 0 0）、（two two 0）和（three 1 1）。在a点中最强的衍射峰来自于TiN的（two two 0）晶面；在b点中TiN的（1 1 1）晶面呈现为最强，而（two two 0）晶面消失了。结合图5中的元素分布可知，Ti的含量在物相变化的过程中起到了重要作用，随着沉积Ti的增加，膜内积聚的内压力促进了相变。
Therefore, the micro beam X-ray diffractometer can be used to monitor the fixed-point performance of TiN films, especially the films plated on micro parts. At the same time, with the help of the microbeam X-ray diffractometer, the micro region of the film can be characterized from the aspects of element composition, element distribution and phase composition. It can help to understand the properties of thin film micro areas, and provide research data for macro film failure or film strengthening.
In order to evaluate the instrument, two-dimensional phase analysis was performed on the sample micro area μ- According to the ability of XRD analysis, a fragment of red and green colored porcelain in the Qing Dynasty was selected as the research object. Adjust the sample table so that the area of interest on the sample surface is clearly displayed in the CCD image, and select the specific target scanning area in the CCD field of view of the control interface through the mouse (Fig. seven). Select a (white glaze), B (red color) and C (green color) in Figure seven μ- XRD analysis. The measurement conditions of µ -xrd analysis are consistent with the above, and μ- The XRD pattern is shown in Figure eight.
It can be seen from Fig. eight that there is a hump between 15 ° ~three5 ° in the XRD spectrum of the white glaze at point a, which is caused by the amorphous phase formed during the high-temperature firing process of the white glaze; At the same time, through comparison with ICCD PDF card, the main crystalline phase in the white glaze of point a is potassium feldspar KalsithreeOeight (PDF two5-061eight)、石英SiOtwo (PDF 46-1045)和莫来石threeAltwoOthree·twoSiOtwo(PDF 15-0sevenseven6), etc; The main crystalline phase in the red color of point B is FetwoOthree(PDF 4seven-1409) and quartz SiOtwo(PDF 46-1045) etc; The main crystalline phase in the green color of point C is PbeightCu(SitwoOseven)three (PDF three1-0464)等。
此外，选择如图seven中two mm×two mm的感兴趣区域，使用微束X射线衍射仪进行µ-XRD二维扫描分析。该区域被划分为two1×two1个被测试点，扫描步距为100 µm，每个点的测量条件为：X射线管电压为three0 kV，电流为0.5 mA，twoθ探测范围为two4.5°到three0.5°，步距角为0.three°，每步探测活时间为0.eight s。由此得到的扫描总谱经数据处理得到Crystal phase distribution of图如图9所示。
Figure 9 Pb in the scanning areaeightCu(SitwoOseven)three、threeAltwoOthree·twoSiOtwo、KAlSithreeOeightAnd FetwoOthreeCrystal phase distribution of
A new type of microbeam X-ray diffractometer is designed and developed by combining capillary X-ray lens technology with X-ray diffraction analysis technology. The microbeam X-ray diffractometer has the ability of nondestructive analysis of the phase structure of micro samples and sample micro regions, and can realize the transformation of the regions of interest in the sample micro regions μ- XRD two-dimensional scanning. At the same time, the instrument can also μ- EDXRF analysis and μ- EDXRF two-dimensional element analysis can provide reference information for the study of phase structure and expand the function of micro beam X-ray diffractometer. Therefore, it has a broad application prospect in the fields of material science, earth science and cultural relics protection.
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程琳，工学博士，美国加州大学尔湾分校访问学者。现任职于北京师范大学核科学与技术学院，教授，博导。长期从事毛细管聚焦的微束X射线分析技术的研究及相关设备的研发；目前已经成功研发出国内首台毛细管聚焦的微束X射线荧光谱仪和毛细管聚焦的X射线衍射仪等设备并开展相关的分析技术及应用研究；作为项目负责人已经承担多项国家自然科学基金、北京市自然科学基金和北京市科技计划项目等,国家自然科学基金评审专家、北京市高新技术企业评审专家和X-ray spectrometry等国际刊物审稿人。e-mail:[email protected]