Fabrication of multilayer Fresnel zone plate for hard X-ray microscopy by atomic layer deposition and focused ion beam milling

• Published in: Vacuum Vol. 209; p. 111776
• Main Authors: Li, Yanli, Lu, Weier, Wang, Shanfeng, Yuan, Qingxi, Kong, Xiangdong, Han, Li, Xia, Yang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2023
• Subjects: Atomic layer deposition; Focused ion beam; Fresnel zone plate; Hard X-ray microscopy; Multilayer; Fresnel zone plate; Multilayer; Atomic layer deposition; Hard X-ray microscopy; Focused ion beam
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/j.vacuum.2022.111776

Fresnel zone plate (FZP) is a widely used optics in X-ray microscopy. In contrast to soft X-ray, high aspect ratio is essential for FZP to focus hard X-ray efficiently. Multilayer FZP (ML-FZP) is a promising solution to fabricate high-aspect-ratio FZP due to the unique sputter-sliced technique. In this work, atomic layer deposition (ALD) and focused ion beam (FIB) milling were utilized to prepare ML-FZP for hard X-ray microscopy. Al2O3/HfO2 ML-FZP with total zone thickness 10 μm was successfully obtained. The zone thickness is much greater than the reported ML-FZPs fabricated by the same method and of great significance to the increase of FZP active region. The ML-FZP with outermost zone width 40 nm and aspect ratio 157 was also tested in transmission X-ray microscopy (TXM) at 9 keV and achieved a 29 nm half-pitch cut-off resolution. •Al2O3/HfO2 hard X-ray Multilayer FZP (ML-FZP) with outermost zone width 40 nm and aspect ratio 157 was successfully obtained by atomic layer deposition (ALD) and focused ion beam (FIB) milling.•A total zone thickness up to 10 μm composed of 213 layers with a nanometer precision scale for each layer was realized for ML-FZP.•The ML-FZP shows imaging capacity in hard X-ray transmission X-ray microscopy with a half-pitch cut-off resolution 29 nm and the diffraction efficiency was about 2.8%.