Li Kenan, Ali Sajid, Wojcik Michael, De Andrade Vincent, Huang Xiaojing, Yan Hanfei, Chu Yong S, Nazaretski Evgeny, Pattammattel Ajith, Jacobsen Chris
Applied Physics, Northwestern University, Evanston, IL 60208, USA.
Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
Optica. 2020 May;7(5):410-416. doi: 10.1364/OPTICA.387445.
Fresnel zone plates are widely used for x-ray nanofocusing, due to their ease of alignment and energy tunability. Their spatial resolution is limited in part by their outermost zone width , while their efficiency is limited in part by their thickness . We demonstrate the use of Fresnel zone plate optics for x-ray nanofocusing with = 16 nm outermost zone width and a thickness of about = 1.8 μm (or an aspect ratio of 110) with an absolute focusing efficiency of 4.7% at 12 keV, and 6.2% at 10 keV. Using partially coherent illumination at 12 keV, the zone plate delivered a FWHM focus of 46 × 60 nm at 12 keV, with the first order coherent mode in a ptychographic reconstruction showing a probe size of 16 nm FWHM. These optics were fabricated using a combination of metal assisted chemical etching and atomic layer deposition for the diffracting structures, and silicon wafer back-thinning to produce optics useful for real applications. This approach should enable new higher resolution views of thick materials, especially when energy tunability is required.
菲涅耳波带片因其易于对准和能量可调性而被广泛用于X射线纳米聚焦。其空间分辨率部分受其最外层带宽度的限制，而其效率部分受其厚度的限制。我们展示了使用菲涅耳波带片光学元件进行X射线纳米聚焦，其最外层带宽度为16纳米，厚度约为1.8微米（或纵横比为110），在12千电子伏时的绝对聚焦效率为4.7%，在10千电子伏时为6.2%。在12千电子伏下使用部分相干照明，该波带片在12千电子伏时提供了46×60纳米的半高宽焦点，在叠层成像重建中的一阶相干模式显示探针尺寸为16纳米半高宽。这些光学元件是通过金属辅助化学蚀刻和原子层沉积相结合的方法制造衍射结构，并对硅片进行背面减薄以生产适用于实际应用的光学元件。这种方法应该能够实现对厚材料的新的更高分辨率的观察，特别是在需要能量可调性的情况下。
