Akan Rabia, Frisk Thomas, Lundberg Fabian, Ohlin Hanna, Johansson Ulf, Li Kenan, Sakdinawat Anne, Vogt Ulrich
KTH Royal Institute of Technology, Department of Applied Physics, Biomedical and X-ray Physics, Albanova University Center, 106 91 Stockholm, Sweden.
MAX IV Laboratory, Lund University, 22 100 Lund, Sweden.
Micromachines (Basel). 2020 Mar 13;11(3):301. doi: 10.3390/mi11030301.
Zone plates are diffractive optics commonly used in X-ray microscopes. Here, we present a wet-chemical approach for fabricating high aspect ratio Pd/Si zone plate optics aimed at the hard X-ray regime. A Si zone plate mold is fabricated via metal-assisted chemical etching (MACE) and further metalized with Pd via electroless deposition (ELD). MACE results in vertical Si zones with high aspect ratios. The observed MACE rate with our zone plate design is 700 nm/min. The ELD metallization yields a Pd density of 10.7 g/cm 3 , a value slightly lower than the theoretical density of 12 g/cm 3 . Fabricated zone plates have a grid design, 1:1 line-to-space-ratio, 30 nm outermost zone width, and an aspect ratio of 30:1. At 9 keV X-ray energy, the zone plate device shows a first order diffraction efficiency of 1.9%, measured at the MAX IV NanoMAX beamline. With this work, the possibility is opened to fabricate X-ray zone plates with low-cost etching and metallization methods.
波带片是X射线显微镜中常用的衍射光学元件。在此，我们提出一种湿化学方法来制造针对硬X射线区域的高纵横比钯/硅波带片光学元件。通过金属辅助化学蚀刻（MACE）制造硅波带片模具，并通过化学镀（ELD）进一步用钯金属化。MACE可形成具有高纵横比的垂直硅区。采用我们的波带片设计观察到的MACE速率为700纳米/分钟。ELD金属化产生的钯密度为10.7克/立方厘米，该值略低于理论密度12克/立方厘米。制造的波带片具有网格设计、1:1的线宽与间距比、30纳米的最外层区宽度以及30:1的纵横比。在9千电子伏特的X射线能量下，该波带片装置在MAX IV NanoMAX光束线上测得的一阶衍射效率为1.9%。通过这项工作，开启了用低成本蚀刻和金属化方法制造X射线波带片的可能性。
