| 1. |
- Chubarova, Elena, et al.
(author)
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Platinum zone plates for hard X-ray applications
- 2011
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In: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 88:10, s. 3123-3126
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Journal article (peer-reviewed)abstract
- We describe the fabrication and evaluation of platinum zone plates for 5–12 kV X-ray imaging and focusing. These nano-scale circular periodic structures are fabricated by filling an e-beam generated mold with Pt in an electroplating process. The plating recipe is described. The resulting zone plates, having outer zone widths of 100 and 50 nm, show good uniformity and high aspect ratio. Their diffraction efficiencies are 50–70% of the theoretical, as measured at the European Synchrotron Radiation Facility. Platinum shows promise to become an attractive alternative to present hard X-ray zone plate materials due to its nano-structuring properties and the potential for zone-plate operation at higher temperatures.
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| 2. |
- Hertz, Hans, et al.
(author)
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Laboratory cryo soft X-ray microscopy
- 2012
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In: Journal of Structural Biology. - : Elsevier. - 1047-8477 .- 1095-8657. ; 177:2, s. 267-272
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Journal article (peer-reviewed)abstract
- Lens-based water-window X-ray microscopy allows two- and three-dimensional (2D and 3D) imaging of intact unstained cells in their near-native state with unprecedented contrast and resolution. Cryofixation is essential to avoid radiation damage to the sample. Present cryo X-ray microscopes rely on synchrotron radiation sources, thereby limiting the accessibility for a wider community of biologists. In the present paper we demonstrate water-window cryo X-ray microscopy with a laboratory-source-based arrangement. The microscope relies on a lambda = 2.48-nm liquid-jet high-brightness laser-plasma source, normal-incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate 2D imaging of test patterns, and intact unstained yeast, protozoan parasites and mammalian cells. Overview 3D information is obtained by stereo imaging while complete 3D microscopy is provided by full tomographic reconstruction. The laboratory microscope image quality approaches that of the synchrotron microscopes, but with longer exposure times. The experimental image quality is analyzed from a numerical wave-propagation model of the imaging system and a path to reach synchrotron-like exposure times in laboratory microscopy is outlined.
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| 3. |
- Hertz, Hans, et al.
(author)
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Laboratory Water-Window X-Ray Microscopy
- 2009
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In: 2009 IEEE LEOS ANNUAL MEETING CONFERENCE PROCEEDINGS. - 9781424436804 ; , s. 48-48
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Conference paper (peer-reviewed)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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| 4. |
- Hertz, Hans M., et al.
(author)
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Laboratory X-ray micro- and nano-imaging
- 2009
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In: Frontiers in Optics (FiO) 2009. - Washington, D.C. : Optical Society of America. - 9781557528780
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Conference paper (peer-reviewed)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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| 5. |
- Hertz, Hans M., et al.
(author)
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Laboratory x-ray micro imaging : Sources, optics, systems and applications
- 2009
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In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
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Journal article (peer-reviewed)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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| 6. |
- Holmberg, Anders, et al.
(author)
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Soft x-ray zone plate fabrication at KTH, Stockholm
- 2009
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In: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 186
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Journal article (peer-reviewed)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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| 7. |
- Holmberg, Anders, et al.
(author)
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Towards 10-nm Soft X-Ray Zone Plate Fabrication
- 2011
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Conference paper (peer-reviewed)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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| 8. |
- Lindblom, Magnus, et al.
(author)
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High-aspect-ratio germanium zone plates fabricated by ractive ion etching in chlorine
- 2009
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In: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 27:2, s. L1-L3
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Journal article (peer-reviewed)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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| 9. |
- Lindblom, Magnus, et al.
(author)
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Nickel-germanium soft x-ray zone plates
- 2009
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In: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 27:3, s. L5-L7
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Journal article (peer-reviewed)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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| 10. |
- Nilsson, Daniel, et al.
(author)
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Thermal stability of tungsten zone plates for focusing hard x-ray free-electron laser radiation
- 2012
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In: New Journal of Physics. - : Institute of Physics (IOP). - 1367-2630. ; 14, s. 043010-
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Journal article (peer-reviewed)abstract
- Diffractive Fresnel zone plates made of tungsten show great promise for focusing hard x-ray free-electron laser (XFEL) radiation to very small spot sizes. However, they have to withstand the high-intensity pulses of the beam without being damaged. This might be problematic since each XFEL pulse will create a significant temperature increase in the zone plate nanostructures and it is therefore crucial that the optics are thermally stable, even for a large number of pulses. Here we have studied the thermal stability of tungsten zone-platelike nanostructures on diamond substrates using a pulsed Nd:YAG laser which creates temperature profiles similar to those expected from XFEL pulses. We found that the structures remained intact up to a laser fluence of 100 mJ cm(-2), corresponding to a 6 keV x-ray fluence of 590 mJ cm-2, which is above typical fluence levels in an unfocused XFEL beam. We have also performed an initial damage experiment at the LCLS hard XFEL facility at SLAC National Accelerator Laboratory, where a tungsten zone plate on a diamond substrate was exposed to 105 pulses of 6 keV x-rays with a pulse fluence of 350 mJ cm-2 without any damage occurring.
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