Fabrication of high-aspect ratio nanogratings for phase-based X-ray imaging

DOI: 10.1002/adfm.202212660

Authors: Martyna Michalska (University College London) , Alessandro Rossi (University College London) , Gašper Kokot (Jožef Stefan Institute) , Callum M. Macdonald (University College London) , Silvia Cipiccia (University College London) , Peter R. T. Munro (University College London) , Alessandro Olivo (University College London) , Ioannis Papakonstantinou (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Functional Materials , VOL 05

State: Published (Approved)
Published: January 2023
Diamond Proposal Number(s): 28831

Abstract: Diffractive optical elements such as periodic gratings are fundamental devices in X-ray imaging – a technique that medical, material science, and security scans rely upon. Fabrication of such structures with high aspect ratios at the nanoscale creates opportunities to further advance such applications, especially in terms of relaxing X-ray source coherence requirements. This is because typical grating-based X-ray phase imaging techniques (e.g., Talbot self-imaging) require a coherence length of at least one grating period and ideally longer. In this paper, the fabrication challenges in achieving high-aspect ratio nanogratings filled with gold are addressed by a combination of laser interference and nanoimprint lithography, physical vapor deposition, metal assisted chemical etching (MACE), and electroplating. This relatively simple and cost-efficient approach is unlocked by an innovative post-MACE drying step with hexamethyldisilazane, which effectively minimizes the stiction of the nanostructures. The theoretical limits of the approach are discussed and, experimentally, X-ray nanogratings with aspect ratios >40 are demonstrated. Finally, their excellent diffractive abilities are shown when exposed to a hard (12.2 keV) monochromatic X-ray beam at a synchrotron facility, and thus potential applicability in phase-based X-ray imaging.

Journal Keywords: collapse behaviors; electrodepositions; metal assisted chemical etching; nanoimprint lithography; phase-based X-ray imaging; X-ray nanogratings

Subject Areas: Technique Development, Materials


Instruments: I13-1-Coherence

Added On: 27/01/2023 09:59

Discipline Tags:

Technique Development - Materials Science Materials Science

Technical Tags:

Imaging