| 1. |
- Bertilson, Michael C., et al.
(författare)
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Zone plate efficiency measurements with a laser-plasma source
- 2007
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Ingår i: Advances in X-Ray/EUV Optics and Components II. - : SPIE. - 9780819468536 ; , s. F7050-F7050
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a compact instrument for rapid and accurate measurements of the absolute and local efficiency of soft x-ray zone plates in the water window [M. Bertilson, et al, Rev. Sci. Instrum 78, 026103 (2007)]. The arrangement is based on a new single-line lambda = 2.88 nm liquid-nitrogen-jet laser-plasma source. The versatility of the instrument enables micro and condenser zone plates with focal lengths in the range from similar to 200 mu m to similar to 100 mm to be measured. We demonstrate an accurate local efficiency map of a in-house fabricated micro zone plate. Furthermore, we show how this compact instrument allows rapid feedback to the fabrication process which is important for future improvements.
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| 2. |
- Bertilson, Michael, et al.
(författare)
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Compact high-resolution differential interference contrast soft x-ray microscopy
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:064104
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate high-resolution x-ray differential interference contrast (DIC) in a compact soft x-ray microscope. Phase contrast imaging is enabled by the use of a diffractive optical element objective which is matched to the coherence conditions in the microscope setup. The performance of the diffractive optical element objective is evaluated in comparison with a normal zone plate by imaging of a nickel siemens star pattern and linear grating test objects. Images obtained with the DIC optic exhibit typical DIC enhancement in addition to the normal absorption contrast. Contrast transfer functions based on modulation measurements in the obtained images show that the DIC optic gives a significant increase in contrast without reducing the spatial resolution. The phase contrast operation mode now available for our compact soft x-ray microscope will be a useful tool for future studies of samples with low absorption contrast.
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| 3. |
- Bertilson, Michael, et al.
(författare)
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First application experiments with the Stockholm compact soft x-ray microscope
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
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Tidskriftsartikel (refereegranskat)abstract
- Most soft x-ray microscopes operating in the water window (lambda = 2.3 - 4.4 nm) rely on synchrotron radiation sources. In the future we believe scientists will use soft x-ray microscopes as one imaging tool among others in their own laboratory. For this purpose we have developed a full field soft x-ray microscope with a laser-plasma source compact enough to fit on an optical table. In this contribution we describe the current status of this microscope now featuring stable operation at lambda = 3.37 nm or lambda = 2.48 nm. In-house fabricated single element zone plates offering the possibility to perform phase contrast imaging have been implemented. We also report on the first application experiments for compact soft x-ray microscopy, including results from studies of clay minerals and colloids existing in nature and results from phase optics experiments. Planned upgrades of the microscope include increasing the source brightness, implementing more efficient condenser optics, and installing a cryo sample stage for tomography. These improvements will open up for further applications, especially in the field of biological imaging.
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| 4. |
- Bertilson, Michael, et al.
(författare)
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High-resolution computed tomography with a compact soft x-ray microscope
- 2009
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Ingår i: Optics Express. - 1094-4087. ; 17:13, s. 11057-11065
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Tidskriftsartikel (refereegranskat)abstract
- Computed tomography based on high-resolution soft x-ray microscopy utilizes the natural contrast for biological specimens provided by the water window (lambda = 2.4 - 4.4 nm) and the high resolving power of zone plate objectives. It is capable of revealing the 3D structure of biological specimens at sub-visible-microscopic resolution. To date, the technique has only been available at synchrotron-based microscopes, which limits the researchers access. In the present paper we demonstrate high-resolution soft x-ray tomography with a laboratory zone-plate-based soft x-ray microscope. The specimen, a diatom mounted on a glass capillary, was reconstructed from a tilt series of 53 images covering 180 using a filtered back projection algorithm. The resolution of the tomogram was estimated to a half period of 140 nm using a differential-phase-residual method. Cryo-fixation, increased source brightness and extended-depth-of-focus objectives are important for pushing the resolution of compact systems for biological samples.
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| 5. |
- Bertilson, Michael, et al.
(författare)
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Laboratory Soft X-Ray Cryo Tomography
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- X-rays allow quantitative high-spatial-resolution three-dimensional (3D) imaging of intact unstained cells. Such 3D imaging is provided by soft x-ray lens-based methods (water-window cryo tomography) and hard x-ray lens-less methods (coherent diffraction imaging) are emerging. However, both methods rely on high-brightness synchrotron-radiation sources, which limit the accessibility of a wider scientific community. Here we show 3D water-window cryo tomography with a laboratory-source-based microscope arrangement. The system relies on a λ=2.48-nm liquid-jet laser-plasma source, normal- incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate imaging of intact unstained yeast, protozoan parasites and mammalian cells. 3D images show noise-limited features close to ~100 nm and intra-cellular structure is classified based on the local absorption coefficient. A comprehensive theoretical model of the tomographic imaging system allows optimization of system parameters and a quantitative estimate of the 3D imaging accuracy. The model includes issues such as non-geometric projections of the thick samples and stray light, and is applicable to laboratory as well as synchrotron-based x-ray microscopes. The model shows that laboratory x-ray cryo tomography will allow quantitative 3D imaging with ~30-nm (half-period) resolution over a full 5 µm object.
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| 6. |
- Bertilson, Michael, et al.
(författare)
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Laboratory soft-x-ray microscope for cryotomography of biological specimens
- 2011
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 36:14, s. 2728-2730
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Tidskriftsartikel (refereegranskat)abstract
- Soft-x-ray cryotomography allows quantitative and high-resolution three-dimensional imaging of intact unstained cells. To date, the method relies on synchrotron-radiation sources, which limits accessibility for researchers. Here we present a laboratory water-window microscope for cryotomography. It is based on a lambda = 2.48nm liquid-jet laser-plasma source, a normal-incidence multilayer condenser, a 30nm zone-plate objective, and a cryotilt sample holder. We demonstrate high-resolution imaging, as well as quantitative tomographic imaging, of frozen intact cells. The reconstructed tomogram of the intracellular local absorption coefficient shows details down to similar to 100nm.
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| 7. |
- Bertilson, Michael, 1979-
(författare)
-
Laboratory soft x-ray microscopy and tomography
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soft x-ray microscopy in the water-window (λ = 2.28 nm – 4.36 nm) is based on zone-plate optics and allows high-resolution imaging of, e.g., cells and soils in their natural or near-natural environment. Three-dimensional imaging is provided via tomographic techniques, soft x-ray cryo tomography. However, soft x-ray microscopes with such capabilities have been based on large-scale synchrotron x‑ray facilities, thereby limiting their accessibility for a wider scientific community. This Thesis describes the development of the Stockholm laboratory soft x-ray microscope to three-dimensional cryo tomography and to new optics-based contrast mechanisms. The microscope relies on a methanol or nitrogen liquid-jet laser-plasma source, normal-incidence multilayer or zone-plate condenser optics, in-house fabricated zone-plate objectives, and allows operation at two wavelengths in the water-window, λ = 2.48 nm and λ = 2.48 nm. With the implementation of a new state-of-the-art normal-incidence multilayer condenser for operation at λ = 2.48 nm and a tiltable cryogenic sample stage the microscope now allows imaging of dry, wet or cryo-fixed samples. This arrangement was used for the first demonstration of laboratory soft x-ray cryo microscopy and tomography. The performance of the microscope has been demonstrated in a number of experiments described in this Thesis, including, tomographic imaging with a resolution of 140 nm, cryo microscopy and tomography of various cells and parasites, and for studies of aqueous soils and clays. The Thesis also describes the development and implementation of single-element differential-interference and Zernike phase-contrast zone-plate objectives. The enhanced contrast provided by these optics reduce exposure times or lowers the dose in samples and are of major importance for harder x-ray microscopy. The implementation of a high-resolution 50 nm compound zone-plate objective for sub-25-nm resolution imaging is also described. All experiments are supported by extensive numerical modelling for improved understanding of partially coherent image formation and stray light in soft x-ray microscopes. The models are useful tools for studying effects of zone plate optics or optical design of the microscope on image formation and quantitative accuracy in soft x-ray tomography.
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| 8. |
- Bertilson, Michael, et al.
(författare)
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Numerical model for tomographic image formation in transmission x-ray microscopy
- 2011
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Ingår i: Optics Express. - 1094-4087. ; 19:12, s. 11578-11583
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Tidskriftsartikel (refereegranskat)abstract
- We present a numerical image-formation model for investigating the influence of partial coherence, sample thickness and depth-of-focus on the accuracy of tomographic reconstructions in transmission x-ray microscopes. The model combines wave propagation through the object by finite difference techniques with Fourier methods. We include a ray-tracing model to analyse the origin of detrimental stray light in zone plate-based x-ray microscopes. These models allow optimization of x-ray microscopy systems for quantitative tomographic imaging of thick objects. Results show that both the depth-of-focus and the reconstructed local absorption coefficient are highly dependent on the degree of coherence of the optical system.
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| 9. |
- Brunskog, Rickard, et al.
(författare)
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Non-prewhitening Observer Applied on Grating-Based and Grating-Less Phase-Contrast Imaging A Simulation Study
- 2024
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Ingår i: Medical Imaging 2024: Physics of Medical Imaging. - : SPIE-Intl Soc Optical Eng.
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Konferensbidrag (refereegranskat)abstract
- Purpose: When implementing differential phase-contrast imaging with current CT detectors the limited pixel size forces one to scan an analyser-grating in front of the detector to resolve the interference pattern. This simulation study compares the approach of using an analyser-grating and the approach of using a high-resolution detector to directly resolve the interference pattern by applying the non-prewhitening observer on dose-matched simulated CT scan reconstructions of the two approaches. Approach: A phantom with two concentric cylinders is used and 1000 CT scans are generated with the inner cylinder present and not present. The non-prewhitening observer is applied to the samples and the ROC curve is extracted, together with the results of a 2AFC test, the CNR, and the detectability. Results: The high-resolution approach shows a 20% increase in the phase AUC compared to the grating-based approach, with a similar increase in the 2AFC test score. The image CNR of the phase shows an increase of 134%, with the detectability increasing by 138% when compared to the grating based approach. Conclusions: An ultra-high-resolution detector, capable of directly resolving the interference pattern of differential phase-contrast imaging could change medical imaging CT as we know it. The implementation in a clinical CT would be simpler, could lower cost, and increase the dose-efficiency due to the obviation of the G2-grating, and at the same time provide an additional two diagnostic signals.
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| 10. |
- Gleber, S. -C, et al.
(författare)
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X-ray stereo microscopy for investigation of dynamics in soils
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186, s. 012104-
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Tidskriftsartikel (refereegranskat)abstract
- The here presented combination of stereo imaging and elemental mapping with soft X-ray microscopy reveals the spatial arrangement of naturally aqueous colloidal systems, e.g. iron oxides in soil colloid clusters. Changes in the spatial arrangement can be induced by manipulating the sample in-situ and thus be investigated directly and as a function of time.
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| 11. |
- Hertz, Hans, et al.
(författare)
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Laboratory Water-Window X-Ray Microscopy
- 2009
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Ingår i: 2009 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS. - 9781424436804 ; , s. 48-48
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Konferensbidrag (refereegranskat)abstract
- We review recent progress in laboratory water-window microscopy including 250 W/0.8 ns/2 kHz laser-plasma liquid-jet sources, 13-nm zone width diffractive optics, diffractive optical elements for phase-contrast microscopy, <25-nm resolution microscopy using compound zone plates, tomography and applications in soil science.
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| 12. |
- Hertz, Hans M., et al.
(författare)
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Laboratory X-ray micro- and nano-imaging
- 2009
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Ingår i: Frontiers in Optics (FiO) 2009. - Washington, D.C. : Optical Society of America. - 9781557528780
-
Konferensbidrag (refereegranskat)abstract
- We summarize recent progress in laboratory x-ray imaging systems based on compact high-brightness liquid-jet sources, including <25 nm soft x-ray zone-plate microscopy and <10 μm (lens-free) hard x-ray phase-contrast imaging.
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| 13. |
- Hertz, Hans M., et al.
(författare)
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Laboratory x-ray micro imaging : Sources, optics, systems and applications
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- We summarize the recent progress in laboratory-scale soft and hard x-ray micro imaging in Stockholm. Our soft x-ray work is based on liquid-jet laser-plasma sources which are combined with diffractive and multilayer optics to form laboratory x-ray microscopes. In the hard x-ray regime the imaging is based on a liquid-metal-jet electron-impact source which provides the necessary coherence to allow phase-contrast imaging with high fidelity.
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| 14. |
- Hertz, Hans M., et al.
(författare)
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Laboratory X-ray microscopy for high-resolution imaging of environmental colloid structure
- 2012
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Ingår i: Chemical Geology. - : Elsevier BV. - 0009-2541 .- 1872-6836. ; 329:SI, s. 26-31
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Tidskriftsartikel (refereegranskat)abstract
- Transmission X-ray microscopy is a uniquely suited technique for studies of environmental colloids since it allows imaging in aqueous media with high spatial resolution, presently down to the 20 nm range. Such nanoscale morphological description of these high-specific-surface-area compounds show promise for improved understanding of soils, sediments or groundwater aquifers. However, present high-quality X-ray microscopes are located at synchrotron radiation facilities resulting in limited applicability and accessibility for colloid scientists. Here we investigate the applicability of a laboratory-scale transmission X-ray microscope for studies of colloids of the environment. The microscope is based on a laser-plasma source in combination with multilayer and zone plate optics. Samples are held at atmospheric pressure in their natural wet state. We show images revealing the nano-scale morphology of the clay nontronite, soils such as chernozem and luvisol, and the mineral hematite, an iron oxide. Comparative studies of dried substances clearly show the need for imaging in the wet state. The image quality approaches that of synchrotron-based microscopes, albeit at longer exposure times. Stereo imaging is investigated as a means for giving 3D information with shorter exposure times than tomography requires. Finally the future development of the laboratory X-ray microscope is discussed, especially with regard to the reduction of exposure times.
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| 15. |
- Holmberg, Anders, et al.
(författare)
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Soft x-ray zone plate fabrication at KTH, Stockholm
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- We present the status of our zone plate and test object fabrication processes along with the latest fabricated components. With our nickel process, zone plates with outermost zone width of 20 nm and zone height of 90 nm have been fabricated. A gold electroplating process has recently been introduced for the fabrication of test objects. The first result for gold gratings with 70 nm period and 135 nm height is shown.
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| 16. |
- Holmberg, Anders, et al.
(författare)
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Towards 10-nm Soft X-Ray Zone Plate Fabrication
- 2011
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Konferensbidrag (refereegranskat)abstract
- In this paper the latest efforts to improve our nanofabrication process for soft x‐ray zone plates is presented. The resolving power, which is proportional to the smallest outermost zone width of the zone plate, is increased by introducing cold development of the electron beam resist that is used for the patterning. With this process we have fabricated Ni zone plates with 13‐nm outermost zone and shown potential for making 11‐nm half‐pitch lines in the electron beam resist. Maintaining the diffraction efficiency of the zone plate is a great concern when the outermost zone width is decreased. To resolve this problem we have developed the so‐called Ni‐Ge zone plate in which the zone plate is build up by Ni and Ge, resulting in an increase of the diffraction efficiency. In a proof‐of‐principle experiment with 25‐nm Ni‐Ge zone plates, we have shown a doubling of the diffraction efficiency. When combined with cold development, the Ni‐Ge process has been shown to work down to 16‐nm half‐pitch. It is plausible that further refinement of the process will make it possible to go to 10‐nm outermost zone widths.
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| 17. |
- Lindblom, Magnus, et al.
(författare)
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High-aspect-ratio germanium zone plates fabricated by ractive ion etching in chlorine
- 2009
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 27:2, s. L1-L3
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the fabrication of soft x-ray germanium zone plates with a process based on reactive ion etching (RIE) in Cl-2. A high degree of anisotropy is achieved by sidewall passivation through cyclic exposure to air. This enables structuring of higher aspect ratios than with earlier reported fabrication processes for germanium zone plates. The results include a zone plate with a 30 nm outermost zone width and a germanium thickness of 310 tun having a first-order diffraction efficiency of 70% of the theoretical value. 25 nm half-pitch gratings were also etched into 310 nut of germanium. Compared to the electroplating process for the commonly used nickel zone plates, the RIE process with Cl-2, for germanium is a major improvement in terms of process reproducibility.
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| 18. |
- Lindblom, Magnus, et al.
(författare)
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Nickel-germanium soft x-ray zone plates
- 2009
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 27:3, s. L5-L7
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 19. |
- Reinspach, Julia, et al.
(författare)
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13 nm high-efficiency nickel-germanium soft x-ray zone plates
- 2011
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 29:1, s. 011012-
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Tidskriftsartikel (refereegranskat)abstract
- Zone plates are used as objectives for high-resolution x-ray microscopy. Both high resolution and high diffraction efficiency are crucial parameters for the performance of the lens. In this article, the authors demonstrate the fabrication of high-resolution soft x-ray zone plates with improved diffraction efficiency by combining a nanofabrication process for high resolution with a process for high diffraction efficiency. High-resolution Ni zone plates are fabricated by applying cold development of electron-beam-patterned ZEP 7000 in a trilayer-resist process combined with Ni-electroplating. High-diffraction-efficiency Ni-Ge zone plates are realized by fabricating the Ni zone plate on a Ge film and then using the finished zone plate as etch mask for anisotropic CHF3 reactive ion etching into the underlying Ge, resulting in a Ni-Ge zone plate with improved aspect ratio and zone plate efficiency. Ni-Ge zone plates with 13 nm outermost zone width composed of 35 nm Ni on top of 45 nm Ge were fabricated. For comparable Ni and Ni-Ge zone plates with an outermost zone width of 15 nm, the diffraction efficiency was measured to be 2.4% and 4.3%, respectively, i.e., an enhancement of a factor of 2.
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| 20. |
- Reinspach, Julia, et al.
(författare)
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Cold-developed electron-beam-patterned ZEP 7000 for fabrication of 13 nm nickel zone plates
- 2009
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 27:6, s. 2593-2596
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Tidskriftsartikel (refereegranskat)abstract
- Cold development was applied to improve the resolution in a trilayer resist that is used for the fabrication of state-of-the-art soft x-ray microscopy zone plates. By decreasing the temperature of the hexyl acetate developer to -50 degrees C, 11 nm half-pitch gratings have been resolved in the electron-beam resist ZEP 7000. 12 nm half-pitch gratings have been successfully transferred, via the intermediate SiO2 hardmask, into the bottom polyimide layer by CHF3 and O-2 reactive ion etching. The trilayer resist, including optimized cold development, has finally been used in an electroplating-based process for the fabrication of nickel zone plates. Zone plates with down to 13 nm outermost zone width have been fabricated and 2.4% average groove diffraction efficiency has been measured for zone plates with 15 nm outermost zone width and a nickel height of 55 nm.
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| 21. |
- Reinspach, Julia, et al.
(författare)
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Process development for improved soft X-ray zone plates
- 2010
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 87:5-8, s. 1583-1586
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate two nanofabrication methods which improve the diffraction efficiency of high-resolution soft X-ray nickel zone plates. First, pulse electroplating is shown to result in uniform diffraction efficiency over the entire zone-plate area. A resulting enhancement of the total efficiency of 20% compared to conventional DC plating was measured. Second, we demonstrate that a high-resolution cold development process can be combined with efficiency-enhancing dry etching into an underlying germanium film. We present 16 nm half-pitch gratings composed of 50 nm nickel on top of 50 nm germanium.
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| 22. |
- Sedlmair, Julia, et al.
(författare)
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Imaging of Vascular Smooth Muscle Cells with Soft X-Ray Spectromicroscopy
- 2011
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Ingår i: Microscopy and Microanalysis. - 1431-9276 .- 1435-8115. ; 17:6, s. 991-1001
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Tidskriftsartikel (refereegranskat)abstract
- Using X-ray microscopy and spectromicroscopy, vascular smooth muscle cells (VSMCs) were imaged, prepared without using additional embedding material or staining, but by applying simple, noncryo fixation techniques. The cells were imaged with a compact source transmission X-ray microscope and a scanning transmission X-ray microscope (STXM). With the STXM, spectromicroscopy was performed at the C K-edge and the Ca L(III,II)-edges. VSMCs were chosen because of their high amount of actin stress fibers, so that the actin cytoskeleton should be visible. Other parts of the cell, such as the nucleus and organelles, were also identified from the micrographs. Both in the spectra and the images, the effects of the different preparation procedures were observable. Furthermore, Ca hotspots were detected and their density is determined.
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| 23. |
- Selin, Mårten, et al.
(författare)
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DiffractX : A Simulation Toolbox for Diffractive X-ray Optics
- 2011
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Ingår i: 10TH INTERNATIONAL CONFERENCE ON X-RAY MICROSCOPY. - : American Institute of Physics (AIP). ; , s. 341-344
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Konferensbidrag (refereegranskat)abstract
- X-ray wavefront propagation is a powerful technique when simulating the performance of x-ray optical components. Using various numerical methods, interesting parameters such as focusing capability and efficiency can be investigated. Here we present the toolbox DiffractX, implemented in MATLAB. It contains many different wave propagation methods for the simulation of diffractive x-ray optics, including Fresnel propagation, the finite difference method (FDM), the thin object approximation, the rigorous coupled wave theory (RCWT), and the finite element method (FEM). All tools are accessed through a graphical interface, making the design of simulations fast and intuitive, even for users with little or no programming experience. The tools have been utilized to characterize realistic as well as idealized optical components. This will aid further developments of diffractive x-ray optics.
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| 24. |
- Thieme, J., et al.
(författare)
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High-resolution imaging of soil colloids in aqueous media with a compact soft X-ray microscope
- 2009
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186, s. 012107-
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Tidskriftsartikel (refereegranskat)abstract
- Colloids play an important role when describing parameters of and processes within soils, sediments or aquifers due to their abundance and their high specific surface area. It is of great importance to visualize the morphology of the structures formed by these particles as close as possible to environmental conditions. With X-ray microscopy colloids from the environment can be imaged directly in aqueous media with high spatial resolution. We demonstrate the first use of a compact laboratory x-ray microscope for studies of colloids from the environment, namely aqueous suspensions of clays and soils. The microscope is based on a high-brightness laser-produced-plasma X-ray source, a multilayer mirror and diffractive optics. The experiments show that such compact X-ray microscopes are reaching the image quality and operational maturity to make a significant impact in fields like environmental sciences.
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| 25. |
- von Hofsten, Olov, et al.
(författare)
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Compact phase-contrast soft X-ray microscopy
- 2009
-
Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
-
Tidskriftsartikel (refereegranskat)abstract
- For nearly all elements, the real part, delta, of the complex index of refraction n (n = 1 - delta + i beta) is larger than the imaginary part, beta, in the x-ray region. Since only beta is used in absorption contrast, phase-contrast imaging techniques which give access to delta are very important. In this paper we present two different implementations of phase contrast in our compact soft x-ray microscope, differential-interference contrast and Zemike phase contrast.
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| 26. |
- von Hofsten, Olof, et al.
(författare)
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Compact Zernike phase contrast x-ray microscopy using a single-element optic
- 2008
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 33:9, s. 932-934
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate Zernike phase contrast in a compact soft x-ray microscope using a single-element optic. The optic is a combined imaging zone plate and a Zernike phase plate and does not require any additional alignment or components. Contrast is increased and inversed in an image of a test object using the Zernike zone plate. This type of optic may be implemented into any existing x-ray microscope where phase contrast is of interest.
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| 27. |
- von Hofsten, Olov, et al.
(författare)
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Simulation of partially coherent image formation in x-ray microscopy - art. no. 67050I
- 2007
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Ingår i: Advances in X-Ray/EUV Optics and Components II. - : SPIE - International Society for Optical Engineering. - 9780819468536 ; , s. I7050-I7050
-
Konferensbidrag (refereegranskat)abstract
- We present the theory and implementation of a numerical model capable of simulating two-dimensional images for an x-ray microscope using partially coherent illumination considerations. Partially coherent illumination is found in all x-ray microscopes and particularly in the latest generation of our in-house compact soft x-ray microscope. This is due to an introduced mismatch in numerical aperture of the condenser and objective zone plate, and will yield diffraction-like artifacts in phase-shifting objects. The numerical model approximates the condenser zone plate as a secondary incoherent source represented by individually coherent but mutually incoherent source emitters, each giving rise to a separate image. A final image is obtained by adding up the image intensities of the individual contributions. The simulation has been a useful tool for investigating the influence of coherence on images in both the mirror and zone plate condenser arrangement of the in-house compact soft x-ray microscope. The latest development included in the program is the effect of astigmatism and partial coherence, where the calculated results show good qualitative agreement with respect to the microscope images.
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| 28. |
- von Hofsten, Olof, et al.
(författare)
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Sub-25-nm laboratory x-ray microscopy using a compound Fresnel zone plate
- 2009
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 34:17, s. 2631-2633
-
Tidskriftsartikel (refereegranskat)abstract
- Improving the resolution in x-ray microscopes is of high priority to enable future applications in nanoscience. However, high-resolution zone-plate optics often have low efficiency, which makes implementation in laboratory microscopes difficult. We present a laboratory x-ray microscope based on a compound zone plate. The compound zone plate utilizes multiple diffraction orders to achieve high resolution while maintaining reasonable efficiency. We analyze the illumination conditions necessary for this type of optics in order to suppress stray light and demonstrate microscopic imaging resolving 25 nm features.
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| 29. |
- von Hofsten, Olof, et al.
(författare)
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Theoretical development of a high-resolution differential-interference-contrast optic for x-ray microscopy
- 2008
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Ingår i: Optics Express. - 1094-4087. ; 16:2, s. 1132-1141
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the theoretical background and development of a differential-interference contrast (DIC) x-ray optic is presented. The single-element optic is capable of high-resolution phase contrast imaging and is compatible with compact sources. It is shown that an understanding of the coherence requirements in this type of imaging is imperative and is explained in detail. The optic is capable of a wavefront separation equal to the resolution of the optic which places only minor constraints on the object illumination.
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