Publications
Publications:
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| Time-Resolved Coherent Diffraction of Ultrafast Structural Dynamics in a Single Nanowire | 2014 |
| Nano Letters 14 (5) 2413–2418 (2014)
Newton, M ; Sao, M ; Fujisawa, Y ; Onitsuka, R ; Kawaguchi, T ; Tokuda, K ; Sato, To ; Togashi, T ; Yabashi, M ; Ishikawa, T ; Ichitsubo, T ; Matsubara, E ; Tanaka, Y ; Nishino, Y The continuing effort to utilize the unique properties present in a number of strongly correlated transition metal oxides for novel device applications has led to intense study of their transitional phase state behavior. Here we report on time-resolved coherent X-ray diffraction measurements on a single vanadium dioxide nanocrystal undergoing a solid–solid phase transition, using the SACLA X-ray Free Electron Laser (XFEL) facility. We observe an ultrafast transition from monoclinic to tetragonal crystal structure in a single vanadium dioxide nanocrystal. Our findings demonstrate that the structural change occurs in a number of distinct stages attributed to differing expansion modes of vanadium atom pairs. | |
| Time-resolved Bragg coherent X-ray diffraction revealing ultrafast lattice dynamics in nano-thickness crystal layer using X-ray free electron laser | 2013 |
| Journal of the Ceramic Society of Japan 121 (1411) 283-286 (2013)
Tanaka, Y ; Ito, K ; Nakatani, T ; Onitsuka, R ; Newton, M ; Sato, T ; Togashi, T ; Yabashi, M ; Kawaguchi, T ; Shimada, K ; Tokuda, K ; Takahashi, I ; Ichitsubo, T ; Matsubara, E ; Nishino, Y Ultrafast time-resolved Bragg coherent X-ray diffraction (CXD) has been performed to investigate lattice dynamics in a thin crystal layer with a nanoscale thickness by using a SASE (Self-Amplified Spontaneous Emission)-XFEL (X-ray Free Electron Laser) facility, SACLA. Single-shot Bragg coherent diffraction patterns of a 100 nm-thick silicon crystal were measured in the asymmetric configuration with a grazing exit using an area detector. The measured coherent diffraction patterns showed fringes extending in the surface normal direction. By using an optical femtosecond laser-pump and the XFEL-probe, a transient broadening of coherent diffraction pattern profile was observed at a delay time of around a few tens of picosecond, indicating transient crystal lattice fluctuation induced by the optical laser. A perspective application of the time-resolved Bragg CXD method to investigate small sized grains composing ceramic materials is discussed. (C)2013 The Ceramic Society of Japan. All rights reserved. | |
| Bonsu: the interactive phase retrieval suite | 2012 |
| Journal of Applied Crystallography 45 840-843 (2012)
Newton, MC ; Nishino, Y; Robinson, IK Coherent X-ray diffraction imaging has received considerable attention as a nondestructive method for probing material structure at the nanoscale. However, tools for reconstructing and analysing data in both two and three dimensions have lagged somewhat behind. Bonsu, the interactive phase retrieval suite, is the first software package that allows real-time visualization of the reconstruction of phase information in both two and three dimensions. It comes complete with an inventory of algorithms and routines for data manipulation and reconstruction. Bonsu is open source, is designed around the Python language (with C++ bindings) and is largely platform independent. Bonsu is made available under version three of the GNU General Public License. | |
| Compressed sensing for phase retrieval | 2012 |
| Physical Review E 85 (5) (2012)
Newton, MC To date there are several iterative techniques that enjoy moderate success when reconstructing phase information, where only intensity measurements are made. There remains, however, a number of cases in which conventional approaches are unsuccessful. In the last decade, the theory of compressed sensing has emerged and provides a route to solving convex optimisation problems exactly via l(1)-norm minimization. Here the application of compressed sensing to phase retrieval in a nonconvex setting is reported. An algorithm is presented that applies reweighted l(1)-norm minimization to yield accurate reconstruction where conventional methods fail. | |
| Coherent X-ray Diffraction Imaging for Strain Analysis on Single ZnO Nanorod | 2011 |
| AIP Conference Proceedings 1399 (2011)
Xiong, G ; Leake, S ; Newton, MC ; Huang, XJ ; Harder, R ; Robinson, IK Strain induced in nanostructure semiconductor materials can result in different electronic properties. Coherent x-ray diffraction (CXD) has emerged as a non-destructive tool for imaging of strain and defects. In this work CXD is applied on a single ZnO nanorod, diffraction patterns from Bragg reflection are used to reconstruct the strain distribution in the samples at a resolution of 40 nm. |