Tong Xujie, Chen Yifang, Mu Chengyang, Chen Qiucheng, Zhang Xiangzhi, Zeng Guang, Li Yuchun, Xu Zijian, Zhao Jun, Zhen Xiangjun, Mao Chengwen, Lu Hongliang, Tai Renzhong
Nanolithography and Application Research Group, School of Information Science and Technology, Fudan University, Shanghai 200433, People's Republic of China.
Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, People's Republic of China.
Nanotechnology. 2023 Mar 7;34(21). doi: 10.1088/1361-6528/acb946.
X-ray microscope as an important nanoprobing tool plays a prevailing role in nano-inspections of materials. Despite the fast advances of high resolution focusing/imaging reported, the efficiency of existing high-resolution zone plates is mostly around 5% in soft x-ray and rapidly goes down to 1%-2% when the resolution approaches 10 nm. It is well known that the rectangular zone shape, beamstop, limited height/width ratios, material absorption of light and structural defects are likely responsible for the limited efficiency. Although zone plates with Kinoform profile are supposed to be efficient, progress for achieving both high resolution (<30 nm) and high efficiency (>5%) have hardly been addressed in soft x-ray. In this work, we propose a compound Kinoform/Fresnel zone plate (CKZP) by combing a dielectric Kinoform zone plate with a 15 nm resolution zone plate. Greyscale electron beam lithography was applied to form the 3D Kinoform zone plate and atomic layer deposition was carried out to form the binary zone plate. Optical characterizations demonstrated 15 nm resolution focusing/imaging with over 7.8% efficiency in soft x-ray. The origin of the efficiency improvement behind the proposed compound lens is theoretically analyzed and discussed.
X射线显微镜作为一种重要的纳米探测工具，在材料的纳米检测中发挥着主导作用。尽管已有高分辨率聚焦/成像方面的快速进展报道，但现有高分辨率波带片在软X射线中的效率大多在5%左右，当分辨率接近10纳米时，效率会迅速降至1%-2%。众所周知，矩形波带形状、光阑、有限的高宽比、材料对光的吸收以及结构缺陷可能是导致效率受限的原因。尽管菲涅耳波带片有望实现高效，但在软X射线中实现高分辨率（<30纳米）和高效率（>5%）的进展却鲜有报道。在这项工作中，我们通过将介电菲涅耳波带片与15纳米分辨率的波带片相结合，提出了一种复合菲涅耳波带片（CKZP）。采用灰度电子束光刻技术形成3D菲涅耳波带片，并通过原子层沉积形成二元波带片。光学表征表明，在软X射线中可实现15纳米分辨率的聚焦/成像，效率超过7.8%。从理论上分析和讨论了所提出的复合透镜提高效率的原因。
