Atom sieve for nanometer resolution neutral helium microscopy
Neutral helium microscopy is a new tool for imaging fragile and/or insulating structures as well as structures with large aspect ratios. In one configuration of the microscope, neutral helium atoms are focused as de Broglie matter waves using a Fresnel zone plate. The ultimate resolution is determin...
| Main Authors: | , , , , , , |
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| Format: | Article |
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American Vacuum Society
2020
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| Online Access: | https://hdl.handle.net/1721.1/126228 |
| _version_ | 1826188678380126208 |
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| author | Flatabø, Ranveig Greve, Martin M. Eder, Sabrina D. Kalläne, Matthias Palau, Adrià Salvador Berggren, Karl K Holst, Bodil |
| author2 | Massachusetts Institute of Technology. Research Laboratory of Electronics |
| author_facet | Massachusetts Institute of Technology. Research Laboratory of Electronics Flatabø, Ranveig Greve, Martin M. Eder, Sabrina D. Kalläne, Matthias Palau, Adrià Salvador Berggren, Karl K Holst, Bodil |
| author_sort | Flatabø, Ranveig |
| collection | MIT |
| description | Neutral helium microscopy is a new tool for imaging fragile and/or insulating structures as well as structures with large aspect ratios. In one configuration of the microscope, neutral helium atoms are focused as de Broglie matter waves using a Fresnel zone plate. The ultimate resolution is determined by the width of the outermost zone. Due to the low-energy beam (typically less than 0.1 eV), the neutral helium atoms do not penetrate solid materials and the Fresnel zone plate therefore has to be a free-standing structure. This creates particular fabrication challenges. The so-called Fresnel photon sieve structure is especially attractive in this context, as it consists merely of holes. Holes are easier to fabricate than the free-standing rings required in a standard Fresnel zone plate for helium microscopy, and the diameter of the outermost holes can be larger than the width of the zone that they cover. Recently, a photon sieve structure was used for the first time, as an atom sieve, to focus a beam of helium atoms down to a few micrometers. The holes were randomly distributed along the Fresnel zones to suppress higher order foci and side lobes. Here, the authors present a new atom sieve design with holes distributed along the Fresnel zones with a fixed gap. This design gives higher transmission and higher intensity in the first order focus. The authors present an alternative electron beam lithography fabrication procedure that can be used for making high transmission atom sieves with a very high resolution, potentially smaller than 10 nm. The atom sieves were patterned on a 35 nm or a 50 nm thick silicon nitride membrane. The smallest hole is 35 nm, and the largest hole is 376 nm. In a separate experiment, patterning micrometer-scale areas with hole sizes down to 15 nm is demonstrated. The smallest gap between neighboring holes in the atom sieves is 40 nm. They have 47011 holes each and are 23.58 μm in diameter. The opening ratio is 22.60%, and the Fresnel zone coverage of the innermost zones is as high as 0.68. This high-density pattern comes with certain fabrication challenges, which the authors discuss. |
| first_indexed | 2024-09-23T08:03:21Z |
| format | Article |
| id | mit-1721.1/126228 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T08:03:21Z |
| publishDate | 2020 |
| publisher | American Vacuum Society |
| record_format | dspace |
| spelling | mit-1721.1/1262282022-09-30T07:11:12Z Atom sieve for nanometer resolution neutral helium microscopy Flatabø, Ranveig Greve, Martin M. Eder, Sabrina D. Kalläne, Matthias Palau, Adrià Salvador Berggren, Karl K Holst, Bodil Massachusetts Institute of Technology. Research Laboratory of Electronics Neutral helium microscopy is a new tool for imaging fragile and/or insulating structures as well as structures with large aspect ratios. In one configuration of the microscope, neutral helium atoms are focused as de Broglie matter waves using a Fresnel zone plate. The ultimate resolution is determined by the width of the outermost zone. Due to the low-energy beam (typically less than 0.1 eV), the neutral helium atoms do not penetrate solid materials and the Fresnel zone plate therefore has to be a free-standing structure. This creates particular fabrication challenges. The so-called Fresnel photon sieve structure is especially attractive in this context, as it consists merely of holes. Holes are easier to fabricate than the free-standing rings required in a standard Fresnel zone plate for helium microscopy, and the diameter of the outermost holes can be larger than the width of the zone that they cover. Recently, a photon sieve structure was used for the first time, as an atom sieve, to focus a beam of helium atoms down to a few micrometers. The holes were randomly distributed along the Fresnel zones to suppress higher order foci and side lobes. Here, the authors present a new atom sieve design with holes distributed along the Fresnel zones with a fixed gap. This design gives higher transmission and higher intensity in the first order focus. The authors present an alternative electron beam lithography fabrication procedure that can be used for making high transmission atom sieves with a very high resolution, potentially smaller than 10 nm. The atom sieves were patterned on a 35 nm or a 50 nm thick silicon nitride membrane. The smallest hole is 35 nm, and the largest hole is 376 nm. In a separate experiment, patterning micrometer-scale areas with hole sizes down to 15 nm is demonstrated. The smallest gap between neighboring holes in the atom sieves is 40 nm. They have 47011 holes each and are 23.58 μm in diameter. The opening ratio is 22.60%, and the Fresnel zone coverage of the innermost zones is as high as 0.68. This high-density pattern comes with certain fabrication challenges, which the authors discuss. 2020-07-16T19:41:50Z 2020-07-16T19:41:50Z 2017-11 Article http://purl.org/eprint/type/JournalArticle 2166-2746 2166-2754 https://hdl.handle.net/1721.1/126228 Flatabø, Ranveig et al. "Atom sieve for nanometer resolution neutral helium microscopy." Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics 35, 6 (November 2016): 06G502 © 2017 American Vacuum Society http://dx.doi.org/10.1116/1.4994330 Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf American Vacuum Society Prof. Berggren via Phoebe Ayers |
| spellingShingle | Flatabø, Ranveig Greve, Martin M. Eder, Sabrina D. Kalläne, Matthias Palau, Adrià Salvador Berggren, Karl K Holst, Bodil Atom sieve for nanometer resolution neutral helium microscopy |
| title | Atom sieve for nanometer resolution neutral helium microscopy |
| title_full | Atom sieve for nanometer resolution neutral helium microscopy |
| title_fullStr | Atom sieve for nanometer resolution neutral helium microscopy |
| title_full_unstemmed | Atom sieve for nanometer resolution neutral helium microscopy |
| title_short | Atom sieve for nanometer resolution neutral helium microscopy |
| title_sort | atom sieve for nanometer resolution neutral helium microscopy |
| url | https://hdl.handle.net/1721.1/126228 |
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