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Limits of Coherent X-ray Diffraction for Imaging Small Crystals

Limits of Coherent X-ray Diffraction for Imaging Small Crystals. Ian Robinson Ivan Vartanyants Franz Pfeiffer Mark Pfeifer Garth Williams. Department of Physics University of Illinois Second International Workshop on Noncrystallographic Phase Retrieval. Outline. Nanocrystal Shapes

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Limits of Coherent X-ray Diffraction for Imaging Small Crystals

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  1. Limits of Coherent X-ray Diffraction for Imaging Small Crystals • Ian Robinson • Ivan Vartanyants • Franz Pfeiffer • Mark Pfeifer • Garth Williams Department of Physics University of Illinois Second International Workshop on Noncrystallographic Phase Retrieval I. K. Robinson, Phasing Workshop, June 2003

  2. Outline • Nanocrystal Shapes • Vortices During Phasing • How small can we go? • Future Directions of CXD I. K. Robinson, Phasing Workshop, June 2003

  3. Lensless X-ray Microscope I. K. Robinson, Phasing Workshop, June 2003

  4. I. K. Robinson, Phasing Workshop, June 2003

  5. SEMS • Au blanket film • Quartz substrate • Annealed at 950°C for 70 hrs. I. K. Robinson, Phasing Workshop, June 2003

  6. Micron-sized gold crystal:(111) Bragg reflection I. K. Robinson, Phasing Workshop, June 2003

  7. Imaging of Lattice Strains I. K. Robinson, Phasing Workshop, June 2003

  8. Symmetrized Data and two best fitsChisq=0.0005 I. K. Robinson, Phasing Workshop, June 2003

  9. 2D Reconstructionschisquare = 0.0005 I. K. Robinson, Phasing Workshop, June 2003

  10. 3D Diffraction Method kf Q=kf - ki ki I. K. Robinson, Phasing Workshop, June 2003

  11. 3D Diffraction Data1 micron Au crystal * Center is Symmetric * I. K. Robinson, Phasing Workshop, June 2003

  12. 111 111 Slices through plan view SEM: I. K. Robinson, Phasing Workshop, June 2003

  13. Generic “Error Reduction” method J. R. Fienup Appl. Opt. 21 2758 (1982) R. W. Gerchberg and W. O. Saxton Optik 35 237 (1972) I. K. Robinson, Phasing Workshop, June 2003

  14. Real-space Constraints in CrystallograhyR. P. Millane, J. Opt. Soc Am. A 13 725 (1996) • ‘Positivity’ constraint (Sayre) • Finite support, molecular envelope • Solvent flattening • Molecular replacement • Non-crystallographic symmetry • Non-uniqueness is ‘pathologically rare’ (d>1) I. K. Robinson, Phasing Workshop, June 2003

  15. cut off “support” Phasing using G-S Algorithm I. K. Robinson, Phasing Workshop, June 2003

  16. Convergence Trajectory wide support narrow support I. K. Robinson, Phasing Workshop, June 2003

  17. Alternation of ER and HIOHelps to avoid stagnation I. K. Robinson, Phasing Workshop, June 2003

  18. Incomplete Reconstruction can be Striped0.5 micron Pb crystal on SiO2 substrate I. K. Robinson, Phasing Workshop, June 2003

  19. Stripes caused by “Vortices”Vortex pairs separated by inverse of stripe spacing I. K. Robinson, Phasing Workshop, June 2003

  20. Result of “Patching” in 2D I. K. Robinson, Phasing Workshop, June 2003

  21. 3D Vortices Form Pairs of Loops I. K. Robinson, Phasing Workshop, June 2003

  22. Vortices are a Cause of Stagnation during Error Reduction Lauren Perskie, UIUC Summer student Number of vortices / 104 Chisquare I. K. Robinson, Phasing Workshop, June 2003

  23. CXD Beamline at APS Sector 34 I. K. Robinson, Phasing Workshop, June 2003

  24. I. K. Robinson, Phasing Workshop, June 2003

  25. Roller-Blade Slits in UHV I. K. Robinson, Phasing Workshop, June 2003

  26. Lensless X-ray Microscope I. K. Robinson, Phasing Workshop, June 2003

  27. CXD from Silver Nanocubes Yugang Sun and Younan Xia, Science 298 2177 (2003) I. K. Robinson, Phasing Workshop, June 2003

  28. 170nm Silver Nanocubes I. K. Robinson, Phasing Workshop, June 2003

  29. Structure in “Yoneda” PeakGrazing-exit diffraction from a 1000A Au polycrystalline film Specular (αf ~ αi) αf ~ αc αf ~ 0

  30. Competitive Grain GrowthC. V. Thompson, Ann. Rev. Mat. Sci. 30 159 (2000) αf~αc αf<αc I. K. Robinson, Phasing Workshop, June 2003

  31. Angle series, 0.01° steps I. K. Robinson, Phasing Workshop, June 2003

  32. Low dislocationdensity GeSi filmsThickness close to critical thicknessDislocations aggregate at interface and glide to surface along {111}T. Spila, UIUC Thesis I. K. Robinson, Phasing Workshop, June 2003

  33. I. K. Robinson, Phasing Workshop, June 2003

  34. GexSi1-x Film Diffraction • 202 Bragg Peak • 2800A film • 2° incidence angle • 8.5 keV • 20μm ×40μm beam • onto KB mirror • 1μm ×1μm focus • 0.5μm sample steps • APS 34-ID-C I. K. Robinson, Phasing Workshop, June 2003

  35. Conclusions and Outlook • Inversion of CXD by ER-HIO methods • Internal structure of Au Nanocrystals • Preservation of coherence upon focussing • Smallest size now down to 170nm • New CXD-Yoneda geometry • Dislocation strain structure may be possible I. K. Robinson, Phasing Workshop, June 2003

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