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Nickel-germanium soft x-ray zone plates
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
Vise andre og tillknytning
2009 (engelsk)Inngår i: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 27, nr 3, s. L5-L7Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This article presents a fabrication process for soft x-ray zone plates in which nickel and germanium are combined to achieve high diffraction efficiency. A nickel zone plate is first fabricated on a germanium film and then used as a hardmask for a CHF3-plasma etch into the germanium. Zone plates with 50-60 nm nickel and 110-150 nm of germanium are presented. The measured diffraction efficiencies were 10%-11% at lambda=2.88 nm, which shows that high efficiency is possible even with thin nickel. Thus, the method has a potential for improving the efficiency of high-resolution zone plates for which the high-aspect-ratio structuring of nickel is difficult.

sted, utgiver, år, opplag, sider
2009. Vol. 27, nr 3, s. L5-L7
Emneord [en]
elemental semiconductors; germanium; light diffraction; nanofabrication; nickel; semiconductor thin films; X-ray microscopy; X-ray optics; zone plates
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-9807DOI: 10.1116/1.3117256ISI: 000266500300001Scopus ID: 2-s2.0-70449726046OAI: oai:DiVA.org:kth-9807DiVA, id: diva2:133130
Merknad
Tidigare titel: High-efficency nickel-germanium soft x-ray zone plates QC 20100728Tilgjengelig fra: 2009-01-07 Laget: 2009-01-07 Sist oppdatert: 2020-01-30bibliografisk kontrollert
Inngår i avhandling
1. Nanofabrication of Diffractive Soft X-ray Optics
Åpne denne publikasjonen i ny fane eller vindu >>Nanofabrication of Diffractive Soft X-ray Optics
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis summarizes the present status of the nanofabrication of diffractive optics, i.e. zone plates, and test objects for soft x-ray microscopy at KTH. The emphasis is on new and improved fabrication processes for nickel and germanium zone plates. A new concept in which nickel and germanium are combined in a zone plate is also presented. The main techniques used in the fabrication are electron beam lithography for the patterning, followed by plasma etching and electroplating for the structuring of the optical materials. The process for fabricating nickel zone plates has been significantly improved. The reproducibility of the electroplating step has been increased by the implementation of an in-situ rate measurement and an end-point detection method. We have also shown that pulse plating can be used to obtain zone plates with a uniform height profile. New plating mold materials have been introduced and electron-beam curing of the molds has been investigated and implemented to increase their mechanical stability so that pattern collapse in the electroplating step can be avoided. The introduction of cold development has improved the achievable resolution of the process. This has enabled the fabrication of zone plates with outermost zone widths down to 16 nm. The nickel process has also recently been adapted to fabrication of gold structures intended for test objects and hard x-ray zone plates. For the fabrication of germanium zone plates we developed a highly anisotropic plasma-etch process using Cl2 feed and sidewall passivation. Germanium zone plates have been fabricated with zone widths down to 30 nm. The diffraction efficiency is comparable to that of nickel zone plates, but the process does not involve electroplating and thus has for potential for highyield fabrication. The combination of nickel and germanium is a new fabrication concept that provides a means to achieve high diffraction efficiency even for thin nickel. The idea is to fabricate a nickel zone plate on a germanium film. The nickel zone plate itself is then used as etch mask for a highly selective CHF3- plasma etch into the germanium layer. Proof of principle experiments showed an efficiency increase of about a factor of two for nickel zone plates with a 50- nm nickel thickness.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2009. s. vii, 71
Serie
Trita-FYS, ISSN 0280-316X ; 2008:57
Emneord
Nanofabrication, Zone plate, x-ray, diffractive x-ray optics, x-ray microscopy
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-9800 (URN)978-91-7415-205-0 (ISBN)
Disputas
2009-02-06, FR4, Roslagstullsbacken 21, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad
QC 20100728Tilgjengelig fra: 2009-01-13 Laget: 2009-01-07 Sist oppdatert: 2011-10-20bibliografisk kontrollert
2. High-Resolution Nanostructuring for Soft X-Ray Zone-Plate Optics
Åpne denne publikasjonen i ny fane eller vindu >>High-Resolution Nanostructuring for Soft X-Ray Zone-Plate Optics
2011 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Diffractive zone-plate lenses are widely used as optics in high-resolution x-ray microscopes. The achievable resolution in such microscopes is presently not limited by the x-ray wavelength but by limitations in zone-plate nanofabrication. Thus, for the advance of high-resolution x-ray microscopy, progress in zone-plate nanofabrication methods are needed.

 

This Thesis describes the development of new nanofabrication processes for improved x-ray zone-plate optics. Cold development of the electron-beam resist ZEP7000 is applied to improve the resolution of soft x-ray Ni zone plates. The influence of developer temperature on resist contrast, resolution, and pattern quality is investigated. With an optimized process, Ni zone plates with outermost zone widths down to 13 nm are demonstrated. To enhance the diffraction efficiency of Ni zone plates, the concept of Ni-Ge zone plates is introduced. The applicability of Ni-Ge zone plates is first demonstrated in a proof-of-principle experiment, and then extended to cold-developed Ni zone plates with outermost zone widths down to 13 nm. For 15-nm Ni-Ge zone plates a diffraction efficiency of 4.3% at a wavelength of 2.88 nm is achieved, which is about twice the efficiency of state-of-the-art 15-nm Ni zone plates. To further increase both resolution and diffraction efficiency of soft x-ray zone plates, a novel fabrication process for W zone plates is developed. High resolution is provided by salty development of the inorganic electron-beam resist HSQ, and cryogenic RIE in a SF6 plasma is investigated for high-aspect-ratio W structuring. We demonstrate W zone plates with 12-nm outermost zone width and a W height of 90 nm, resulting in a 30% increase in theoretical diffraction efficiency compared to 13-nm efficiency-enhanced Ni-Ge zone plates. In addition to soft x-ray zone plates, some lenses for hard x-ray free-electron-laser applications were also fabricated during this Thesis work. Fabrication processes for the materials W, diamond, and Pt were developed. We demonstrate Pt and W-diamond zone plates with 100-nm outermost zone width and respective diffraction efficiencies of 8.2% and 14.5% at a photon energy of 8 keV.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2011. s. xii, 70
Serie
Trita-FYS, ISSN 0280-316X ; 2011:55
Emneord
zone plates; x-ray optics; x-ray microscopy; high resolution; nanofabrication; electron beam lithography; reactive ion etching; tungsten; nickel; germanium
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-47409 (URN)978-91-7501-175-2 (ISBN)
Disputas
2011-12-02, FA31, Roslagstullsbacken 21, KTH/Albanova, Stockholm, 10:00 (engelsk)
Opponent
Veileder
Merknad
QC 20111114Tilgjengelig fra: 2011-11-14 Laget: 2011-11-08 Sist oppdatert: 2011-11-14bibliografisk kontrollert

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