Coherent xray diffraction from single Au microcrystal Phase

Coherent x-ray diffraction from single Au microcrystal: Phase retrieval F. Picca(1), V. Chamard(2), F. Livet(2), F. Bley(2), M. de Boissieu(2) K. Ludwig(3) and I. K. Robinson(4) (1) Departement of Physics, Mc. Gill University, 3600 University Street, Montreal, PQ, H 3 A 2 T 8, Canada, (2) LTPCM, 1130 rue de la piscine, 38402 Saint Martin d’Hères, France, (3) Department of Physics, Boston University 590 Commonwealth Avenue, Boston MA 02215, USA, (4) Department of Physics and Materials Research Laboratory, University of Illinois, Urbana, USA. Principles of the 3 D reconstruction from a single microcrystal coherence defining slits inversion program a L D xt = D/2 a xl = 2/2 D coherent beam xt > L phase guessing finite size effects broaden Bragg peak oversampling Experimental set-up E = 7. 9 ke. V = 1. 564 Ǻ No assumption !! Inversion program direct illumination CCD [3] 6. 2 m 15 cm + 384 576 pixels 22 m 2 q(111) shape and strain 3 D reconstruction [1, 2] set of random phases real space image #n 500 frames 5 s FT [4] diffraction pattern #n # n+1 r > 0, atoms self-adaptable support, . . . 116 cm 50 m 300 m 1 m xt 2 m xl 0. 5 m data treatments - dark noise - cosmic rays I = Iexp ? modified real space image #n First attempts : Au microcrystals modified diffraction pattern #n FT-1 real space image measurements performed on BM 2 beamline 4 single bunch, = 1. 564 Ǻ (111) Bragg reflection DQ 10 -3 nm-1 x, y 1000 Ǻ Au film on Si. O 2/Si substrate, annealed for a few hours at about 1000°C dewetting, Au microcrystal Dq = 0° FT 30 iterations Dq = -0. 6° Dq = +0. 6° FWHM 700 nm Dq = -0. 4° Dq = +0. 4° 100 nm Dq = -0. 2° Dq = +0. 2° Problems many possibilities: - coherence length, - degradation of coherence (optics, windows…), - sample stability, - strains, … References [1] I. K. Robinson, I. A. Vartanyants, G. J. Williams, M. A. Pfeifer, and J. A. Pitney Phys. Rev. Lett. 87, 195505 (2001), [2] G. J. Williams, M. A. Pfeifer, I. A. Vartanyants and I. K. Robinson, Phys. Rev. Lett. 90, 175501 (2003), [3] F. Livet, F. Bley, J. Mainville, R. Caudron, S. G. J. Mochrie, E. Geissler, G. Dolino, D. Abernathy, G. Grübel and M. Sutton, Nuc. Instr. Meth. Phys. 451, 596 (2000), [4] J. R. Fienup, Appl. Opt. 21, 2758 (1982), R. W. Gerchberg and W. O. Saxton, Optik (Stuttgart) 35, 237 (1972).