Investigations On Preparation And Performance Of X-ray Fresnel Zone Plates With Super Large Aspect Ratios

The X-ray microscopic imaging analysis technology developed based on the synchrotron radiation large scientific device has the characteristics of diverse imaging mechanisms and rich substrates.It can perform non-destructive three-dimensional detection of the microstructure of integrated circuit devices,biological cells,the spatial distribution of specific elements in samples,and phase transition in battery charging and discharging processes.X-ray Fresnel zone plates is the core element in the X-ray microscopy imaging analysis technology,which can realize the focus and imaging of X-rays at the same time.The outermost ring width of its structural parameters determines its imaging resolution.The smaller the outermost ring width,the higher the imaging resolution.The diffraction efficiency is related to its own aspect ratio（the ratio of the lens height/the outermost ring width）.Large aspect ratio,high diffraction efficiency.In this thesis,according to the characteristics of the imaging optical paths of Beijing Synchrotron Radiation（4W1A）and Shanghai Light Source（BL08U1A）,the structure of Fresnel zone plates is designed,and a focused ion beam slicing method based on atomic layer deposition technology is proposed.An 8 Ke V hard X-ray Fresnel zone plates with an outermost ring width of 40 nm,a height of 6.2μm and an aspect ratio of 155:1 as well as a 500 e V soft zone plates with an outermost ring width of 20nm,a height of 330 nm and an aspect ratio of 16.5:1 X-ray Fresnel zone plates were prepared,and the focus imaging performance tests of the Fresnel zone plates were carried out at Beijing Synchrotron Radiation（4W1A）and Shanghai Light Source（BL08U1A）imaging line stations.The mainresults are as follows:（1）The structural characteristics of the Fresnel zone plates are introduced;the basic principle of focusing imaging is explained.The relationship between the diffraction efficiency of the hard X-ray Fresnel zone plates with six material combinations of Al₂O₃/HfO₂,Al₂O₃/Ir,Al₂O₃/Ta₂O₅,Si O₂/HfO₂,Si O₂/Ir and Si O₂/Ta₂O₅and X-ray energy and zone plates height have been simulated and calculated.The effects of the diffraction efficiency,zone plates height,and outermost ring width of the500 e V soft X-ray Fresnel zone plates on the diffraction efficiency of Fresnel zone plates are also calculated by simulations of Al₂O₃/HfO₂,Al₂O₃/Ir,Al₂O₃/Si O₂and Al₂O₃/Ta₂O₅.It is determined that Al₂O₃/HfO₂is the ring zone material of the subsequent multilayer Fresnel zone plates.The optical path characteristics of the Beijing synchrotron radiation（4W1A）hard X-ray imaging line station and the Shanghai light source（BL08U1A）soft X-ray imaging line station combined with the application X-ray band requirements are analyzed,and structural parameters of design for 8 Ke V hard X-ray and 500 e V soft X-ray Fresnel zone plates are given.（2）The technology of fabricating tungsten wire substrates with smooth surface based on electrolytic polishing was studied,and tungsten wires with a surface roughness of 4.09 nm and a diameter of about 55μm were prepared.The preparations of Al₂O₃,HfO₂monolayer films and Al₂O₃/HfO₂multilayer films on the surface of silicon wafers and core filaments using a dual-cavity fast atomic layer deposition system were investigated.The film properties were characterized by spectroscopic ellipsometer AFM and SEM.Finally,with the polished tungsten wire,optical fiber and iron-nickel alloy wire as the central substrates,the multi-layer film ring belt structure with a thickness of10μm was grown.（3）The lens slicing technology based on focused ion beam micro-nano processing is studied.Two X-ray Fresnel zone plates are cut,packaged,polished and installed.The width and height of the outermost ring are 40 nm@6.2μm and 20 nm@330 nm,respectively.The focusing performance and imaging resolution of the two zone plates after installation are tested in Beijing Synchrotron Radiation and Shanghai Light Source.A complete tungsten needle tip image and an optimal resolution of 50 nm are obtained.The preliminary test result of the diffraction efficiency for the Fresnel zone plates is 1.5%.