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Fabrication and characterization of a condenser zone plate for compact x-ray microscopy
KTH, Superseded Departments, Physics.
KTH, Superseded Departments, Physics.ORCID iD: 0000-0003-2745-6289
KTH, Superseded Departments, Physics.
KTH, Superseded Departments, Physics.
Show others and affiliations
2004 (English)In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 22, no 3, 1118-1122 p.Article in journal (Refereed) Published
Abstract [en]

We describe the in-house fabrication and characterization of a condenser zone plate for a compact laser-plasma-based soft x-ray microscope operating at 2.478 nm wavelength. The fabricated condenser has a diameter of 4.53 mm and an outermost zone width of 49 nm. The pattern is generated by a small-write-field e-beam lithography system and 656 single, 100 mum wide write fields are stitched together to obtain the whole pattern. An in-house method based on a laser-plasma source was developed to characterize the condenser zone plate with regards to diffraction efficiency and imaging properties. The measured groove efficiency of the fabricated condenser zone plate was determined to 11%+/-2% and the imaging properties were found to follow the expectations concerning the object field illumination purpose in the x-ray microscope. The in-house characterization method allows faster process improvement in the small-scale laboratory compared to presently used synchrotron-based methods.

Place, publisher, year, edition, pages
2004. Vol. 22, no 3, 1118-1122 p.
Keyword [en]
Charge coupled devices; Diffraction; Lasers; Lithography; Microscopic examination; Plasmas; Plates (structural components); Scanning electron microscopy; Statistical methods; X ray microscopes; Condenser zone plates (CZP); Multilayer mirrors; Synchrotron radiation sources; Capacitors
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-7016DOI: 10.1116/1.1738671ISI: 000222481400043Scopus ID: 2-s2.0-3242657331OAI: oai:DiVA.org:kth-7016DiVA: diva2:11891
Note
QC 20100616Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Compact Soft X-Ray Microscopy: Sources, Optics and Instrumentation
Open this publication in new window or tab >>Compact Soft X-Ray Microscopy: Sources, Optics and Instrumentation
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis describes the development of a sub-60-nm full-period resolution compact soft x-ray microscope operating in the water-window region (2.3-4.4 nm). Soft x-ray water-window microscopy is a powerful technique for high-resolution imaging of organic materials exploiting the natural contrast mechanism between carbon and oxygen, cf. Sect. 4.1. The thesis discusses the components of, as well as the integration of the microscope, including liquid-jet laser-plasma x-ray sources, optics, simulations, and image-processing tools.

Liquid-jet-target laser-plasma sources for generation of soft x-rays and extreme-ultraviolet radiation are compact sources with high brightness. The work focused on improved target stability, decreased debris, and accurate source characterization. For x ray microscopy applications a liquid-jet target delivery system allowing cryogenic liquids was developed. Source characterization was performed for two different liquid-jet targets: Methanol and liquid nitrogen. For extreme-ultraviolet lithography applications, the potential use of a liquid-tin-jet laser-plasma source was explored including conversion efficiency and debris measurements.

High quality optics are essential in the development of compact x-ray microscopes. For soft x-ray wavelengths, zone plates and multilayer mirrors are used to focus or redirect radiation. This thesis describes the development and characterization of a condenser zone plate suitable for use in a compact soft x-ray microscope operating at λ = 2.478 nm. It also investigates the possibility to perform differential interference contrast microscopy in the water window using a single diffractive optical element. An arrangement for rapid and accurate determination of absolute and local diffraction efficiency of soft x-ray zone plates using a compact laser-plasma source has been developed. The instrument is used to characterize the zone plates fabricated at the Biomedical & X-Ray Physics division at KTH. Through a collaboration with the Fraunhofer-Institut in Jena, Germany, a large diameter spherical Cr/Sc multilayer mirror, suitable as condenser in the compact x-ray microscope, was developed and characterized. The mirror is designed for λ = 3.374 nm and shows a high, and uniform reflectivity of 3%. This increases the photon flux by an order of magnitude compared to the W/B4C mirrors previously used.

The thesis describes the development of a compact soft x-ray microscope with sub-60-nm full-period resolution. It can operate at two different wavelengths in the water window using the soft x-ray laser-plasma sources combined with the condenser optics described above. Imaging is performed by zone plate objectives. The microscope is capable of imaging hydrated biological samples with thicknesses up to ~10 μm. Improvements made to the mechanical design has turned it into a user friendly instrument allowing daily operation. A numerical method was developed to study the effects of partially coherent illumination on 2D imaging. To stimulate experiments on functional imaging in x-ray microscopy an image-analysis algorithm for identifying colloidal-gold particles was developed. Size selective identification and localization of single gold particles down to a diameter of 50 nm was demonstrated.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 59 p.
Series
Trita-FYS, ISSN 0280-316X ; 2007:25
Keyword
soft x-ray microscopy, water window, compact, laser plasma, liquid jet, zone plate optics
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-4342 (URN)978-91-7178-613-5 (ISBN)
Public defence
2007-05-04, FD 5, Albanova, Roslagstullsbacken 21, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20100819Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2010-08-20Bibliographically approved
2. Nanofabrication of Zone Plate Optics for Compact Soft X-Ray Microscopy
Open this publication in new window or tab >>Nanofabrication of Zone Plate Optics for Compact Soft X-Ray Microscopy
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This Thesis describes the development of the KTH/Stockholm nanofabrication process for diffractive soft x-ray optics. The effort is motivated by the need for and requirement of specially designed diffractive optics and test objects for compact x-ray microscopy as well as optics for other applications such as phase imaging. The optics have been fabricated in-house, in the KTH Nanofabrication Laboratory.

The nanofabrication process is based on electron-beam lithography in combination with reactive ion etching (RIE) and nickel electroplating. This process has successfully been used for the fabrication of micro zone plates, condenser zone plates, diffractive optical elements for differential-interference microscopy, and different test structures. Optics with electroplated feature sizes down to 25 nm have been fabricated with high aspect-ratios. Special consideration has been given the reproducibility and optimization of the process parameters. This is essential for improving the yield and quality of the fabricated optics. The work includes, e.g., improved e-beam writing strategies and controlled electroplating. Furthermore, a high diffraction efficiency is necessary for our applications, which are based on compact low-power sources. This requires the fabrication of optics with a high and uniform aspect ratio. For this purpose the electroplating process step has been improved with an in-situ light-transmission-based thickness control method for optimum mold filling, and pulse and pulse-reverse techniques for uniform plating.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006
Series
Trita-FYS, ISSN 0280-316X ; 2006:41
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-4045 (URN)91-7178-390-3 (ISBN)
Public defence
2006-06-16, Sal FD5, AlbaNova univ centrum, Roslagstullsbacken 21, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100616Available from: 2006-06-08 Created: 2006-06-08 Last updated: 2010-06-16Bibliographically approved

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Holmberg, AndersHertz, Hans

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