Search

We propose a coherent x-ray zoom condenser lens composed of two-stage deformable Kirkpatrick-Baez mirrors. The lens delivers coherent x-rays with a controllable beam size, from one micrometer to a few tens of nanometers, at a fixed focal position. The lens is suitable for diffractive and scanning microscopy. We also propose non-scanning coherent diffraction microscopy for extended objects by using an apodized focused beam produced by the lens with a spatial filter. The proposed apodized-illumination method will be useful in highly efficient imaging with ultimate storage ring sources, and will also open the way to single-shot coherent diffraction microscopy of extended objects with x-ray free-electron lasers. (C) 2013 Optical Society of America

We propose a coherent x-ray zoom condenser lens composed of two-stage deformable Kirkpatrick-Baez mirrors. The lens delivers coherent x-rays with a controllable beam size, from one micrometer to a few tens of nanometers, at a fixed focal position. The lens is suitable for diffractive and scanning microscopy. We also propose non-scanning coherent diffraction microscopy for extended objects by using an apodized focused beam produced by the lens with a spatial filter. The proposed apodized-illumination method will be useful in highly efficient imaging with ultimate storage ring sources, and will also open the way to single-shot coherent diffraction microscopy of extended objects with x-ray free-electron lasers. (C) 2013 Optical Society of America

Yukio Takahashi, Akihiro Suzuki, Shin Furutaku, Kazuto Yamauchi, Yoshiki Kohmura, and Tetsuya Ishikawa, "High-resolution and high-sensitivity phase-contrast imaging by focused hard x-ray ptychography with a spatial filter", Appl. Phys. Lett. 102, 094102 (2013) https://doi.org/10.1063/1.4794063., We demonstrate high-resolution and high-sensitivity x-ray phase-contrast imaging of a weakly scattering extended object by scanning coherent diffractive imaging, i.e., ptychography, using a focused x-ray beam with a spatial filter. We develop the x-ray illumination optics installed with the spatial filter to collect coherent diffraction patterns with a high signal-to-noise ratio. We quantitatively visualize the object with a slight phase shift ([formula omitted]) at spatial resolution better than 17 nm in a field of view larger than [formula omitted]. The present coherent method has a marked potential for high-resolution and wide-field-of-view observation of weakly scattering objects such as biological soft tissues.

Yukio Takahashi, Akihiro Suzuki, Shin Furutaku, Kazuto Yamauchi, Yoshiki Kohmura, and Tetsuya Ishikawa, Phys. Rev. B 87, 121201, 2013., We experimentally demonstrate the visualization of nanoscale dislocation strain fields in a thick silicon single crystal by a coherent diffraction imaging technique called Bragg x-ray ptychography. We also propose that the x-ray microbeam carrying orbital angular momentum is selectively produced by coherent Bragg diffraction from dislocation singularities in crystals. This work not only provides us with a tool for characterizing dislocation strain fields buried within extended crystals but also opens up new scientific opportunities in femtosecond spectroscopy using x-ray free-electron lasers.

Jangwoo Kim, Takahisa Koyama, Hirokatsu Yumoto, Ayaka Nagahira, Satoshi Matsuyama, Yasuhisa Sano, Makina Yabashi, Haruhiko Ohashi, Tetsuya Ishikawa, and Kazuto Yamauchi "Damage characteristics of platinum/carbon multilayers under x-ray free-electron laser irradiation", Proc. SPIE 8848, Advances in X-Ray/EUV Optics and Components VIII, 88480S (27 September 2013); https://doi.org/10.1117/12.2022735.

Taito Osaka, Makina Yabashi, Yasuhisa Sano, Kensuke Tono, Yuichi Inubushi, Takahiro Sato, Kanade Ogawa, Satoshi Matsuyama, Tetsuya Ishikawa, and Kazuto Yamauchi "Thin crystal development and applications for hard x-ray free-electron lasers", Proc. SPIE 8848, Advances in X-Ray/EUV Optics and Components VIII, 884804 (27 September 2013); https://doi.org/10.1117/12.2023465.

Hiroki Nakamori, Satoshi Matsuyama, Shota Imai, Takashi Kimura, Yasuhisa Sano, Yoshiki Kohmura, Kenji Tamasaku, Makina Yabashi, Tetsuya Ishikawa, and Kazuto Yamauchi, "Experimental and simulation study of undesirable short-period deformation in piezoelectric deformable x-ray mirrors", Review of Scientific Instruments 83(5), 053701 (2012) https://doi.org/10.1063/1.4709499., To construct adaptive x-ray focusing optics whose optical parameters can be varied while performing wavefront correction, ultraprecise piezoelectric deformable mirrors have been developed. We computationally and experimentally investigated undesirable short-period deformation caused by piezoelectric actuators adhered to the substrate during mirror deformation. Based on the results of finite element method analysis, shape measurements, and the observation of x-ray reflection images, a guideline is developed for designing deformable mirrors that do not have short-period deformation errors. © 2012 American Institute of Physics.

Yukio Takahashi, Hideto Kubo, Yoshinori Nishino, Hayato Furukawa, Ryosuke Tsutsumi, Kazuto Yamauchi, Tetsuya Ishikawa, and Eiichiro Matsubara, "An experimental procedure for precise evaluation of electron density distribution of a nanostructured material by coherent x-ray diffraction microscopy", Review of Scientific Instruments 81(3), 033707 (2010) https://doi.org/10.1063/1.3361265., We developed a coherent x-ray diffraction microscopy (CXDM) system that enables us to precisely evaluate the electron density of an isolated sample. This system enables us to determine the dose per surface unit of x rays illuminated onto an isolated sample by combining incident x-ray intensity monitoring and the CXDM of a reference sample. By using this system, we determined the dose of x rays illuminated onto a nanostructured island fabricated by focused-ion-beam chemical vapor deposition and derived the electron density distribution of such a nanostructured island. A projection image of the nanostructured island with a spatial resolution of 24.1 nm and a contrast resolution higher than 2.3× 107 electrons/pixel was successfully reconstructed. © 2010 American Institute of Physics.

Yukio Takahashi, Yoshinori Nishino, Ryosuke Tsutsumi, Nobuyuki Zettsu, Eiichiro Matsubara, Kazuto Yamauchi, and Tetsuya Ishikawa. Phys. Rev. B 82(21), 214102 (2010)., Hard x-ray diffraction microscopy enables us to observe thick objects at high spatial resolution. The resolution of this method is limited, in principle, by only the x-ray wavelength and the largest scattering angle recorded. As the resolution approaches the wavelength, the thickness effect of objects plays a significant role in x-ray diffraction microscopy. In this paper, we report high-resolution hard x-ray diffraction microscopy for thick objects. We used highly focused coherent x rays with a wavelength of ∼0.1 nm as an incident beam and measured the diffraction patterns of a ∼150-nm -thick silver nanocube at the scattering angle of ∼3°. We observed a characteristic contrast of the coherent diffraction pattern due to only the thickness effect and collected the diffraction patterns at nine incident angles so as to obtain information on a cross section of Fourier space. We reconstructed a pure projection image by the iterative phasing method from the patched diffraction pattern. The edge resolution of the reconstructed image was ∼2 nm, which was the highest resolution so far achieved by x-ray microscopy. The present study provides us with a method for quantitatively observing thick samples at high resolution by hard x-ray diffraction microscopy. © 2010 The American Physical Society.

Takashi Kimura, Hidekazu Mimura, Soichiro Handa, Hirokatsu Yumoto, Hikaru Yokoyama, Shota Imai, Satoshi Matsuyama, Yasuhisa Sano, Kenji Tamasaku, Yoshiki Komura, Yoshinori Nishino, Makina Yabashi, Tetsuya Ishikawa, and Kazuto Yamauchi , "Wavefield characterization of nearly diffraction-limited focused hard x-ray beam with size less than 10 nm", Review of Scientific Instruments 81(12), 123704 (2010) https://doi.org/10.1063/1.3509384., In situ wavefront compensation is a promising method to realize a focus size of only a few nanometers for x-ray beams. However, precise compensation requires evaluation of the wavefront with an accuracy much shorter than the wavelength. Here, we characterized a one-dimensionally focused beam with a width of 7 nm at 20 keV using a multilayer mirror. We demonstrate that the wavefront can be determined precisely from multiple intensity profiles measured around the beamwaist. We compare the phase profiles recovered from intensity profiles measured under the same mirror condition but with three different aperture sizes and find that the accuracy of phase retrieval is as small as 12. © 2010 American Institute of Physics.

Hideyuki Hara, Yoshitada Morikawa, Yasuhisa Sano, and Kazuto Yamauchi Phys. Rev. B 79, 153306 (2009)., We study the effect of adsorbates on the relative stability of hexagonal and cubic stacking sequences at the topmost SiC bilayers of 4H-SiC (0001) -1×1 surfaces using first-principles calculations. We investigate F-terminated, OH-terminated, H-terminated, and clean surfaces, and in all cases, the cubic structure is more stable than the hexagonal structure. The energy difference between the two structures, however, significantly depends on adsorbates and is largest on the clean surface while it is smallest on the H-terminated surface. Stabilization of the cubic structure at F-terminated and OH-terminated surfaces is in contradiction to a simple argument based on the electrostatic interaction and we attribute it to orbital hybridization between occupied states of adsorbates and unoccupied states of the substrate surface. The present results suggest a possible means of controlling step bunching and the SiC stacking sequence by surface adsorbates. © 2009 The American Physical Society.

Takahashi Y., Kubo H., Furukawa H., et al. Development of incident X-ray flux monitor for coherent X-ray diffraction microscopy. Journal of Physics: Conference Series, 186, , 012060. https://doi.org/10.1088/1742-6596/186/1/012060., 9TH INTERNATIONAL CONFERENCE ON X-RAY MICROSCOPY 21–25 July 2008, Zürich, Switzerland, An incident X-ray flux monitor for coherent X-ray diffraction microscopy was developed. The intensities of x-rays passing through the sample were measured using an X-ray photodiode, with the simultaneous measurement of the X-ray diffraction intensities of the sample. As a result of the normalization of the X-ray diffraction intensities by the incident X-ray flux determined from the monitor, the fluctuation of the speckle intensities was successfully suppressed. © 2009 IOP Publishing Ltd.

Hidekazu Mimura, Hirokatsu Yumoto, Satoshi Matsuyama, Soichiro Handa, Takashi Kimura, Yasuhisa Sano, Makina Yabashi, Yoshinori Nishino, Kenji Tamasaku, Tetsuya Ishikawa, and Kazuto Yamauchi Phys. Rev. A 77, 015812 (2008)., We present a remarkably accurate method for determining the wave field of an x-ray nanobeam. The intensity profile of a beam was directly measured over a range of three orders of magnitude while its phase distribution was successfully recovered using an iterative algorithm. The evolution of the wave field along the beam propagation direction was precisely simulated, and there was good agreement with the experimental results.

An element-specific coherent x-ray imaging technique using anomalous x-ray scattering in the hard x-ray region was first demonstrated. Coherent x-ray diffraction patterns of a sample composed of 500-nm-thick Ni and Cu layers were measured at incident x-ray energies around the Ni K absorption edge. Non-center-symmetric diffraction patterns due to anomalous scattering phenomenon in the hard x-ray region were observed. Symmetricity of the diffraction pattern was quantitatively analyzed by numerically simulating the x-ray wave field behind the sample position using the Rytov approximation. By calculating the difference between the intensities of reconstructed images of different energies, an image of the Ni layers could be derived although it was not enough to identify precisely. This method is widely applicable to nondestructive analysis of nanometer-scale elemental distribution of materials buried within thick and high-Z samples.