Holographic Imaging of Atomic Structure: Where Is It and Where Can It Go? C.S. Fadley

1. Holographic Imaging of Atomic Structure: Where Is It and Where Can It Go? C.S. Fadley UC Davis Physics and LBNL Materials Sciences Collaborators: S. Marchesini, N. Mannella, A. Nambu, S. Ritchey, L. Zhao-- LBNL Material Sciences and UCD (experiment, theory) D. Shuh, G. Bucher--LBNL-Chemical Sciences (solid state detector) L. Fabris, N. Madden--LBNL Eng. (solid state detector) W. Stolte, A.S. Schlachter--ALS (BL 9.3.1) A. Thompson--ALS (BL 11.3.1) M.A. Van Hove, S. Omori--LBNL Materials Sciences (theory) E. Rotenberg, J. Denlinger, M. Howells, Z. Hussain, ALS (experiment) A. Szöke--LLNL (theory) S.P. Cramer, U. Bergmann--UCD and LBNL Physical Biosciences V.K. Yachandra,T.N. Earnest, LBNL Physical Biosciences M. Tegze, G. Faigel--Budapest M. Belakhovsky--Grenoble, ESRF J. Garcia de Abajo--San Sebastian (theory)

2. Direct or Inside-Source Holography Exciting beamEmitted source wave X-ray/Electron Auger electron (Tonner) X-ray Photoelectron (Szöke, Barton) X-ray Fluorescent x-ray (Tegze, Faigel) Electron Incoherently scattered/ Kikuchi electrons (Saldin, de Andres) Electron Bremsstrahlung x-ray + filter (Sorensen et al.) Neutron Incoherently scattered neutrons (from protons) (Sur et al.) Detector (scanned) Hologram Reference wave Emitted source wave Scattered object/subject waves Exciting beam Emitter = “inside source” Scattering centers: atoms, nuclei Inverse or Inside-Detector Holography Exciting beamEmitteddetected = source wavewave X-ray Fluorescent x-ray Gamma ray/X-ray Conversion e- (nuclear resonance) or gamma ray Neutron Gamma ray (nuclear excitation) Detector (fixed) Exciting beam (scanned) Reference wave Emitted detected wave Emitter = “inside detector” Scattered object/subject waves

3. The basic imaging ideas: (Gabor; Helmholtz-Kirchoff; Wolf; Szöke; Barton-Tong) Energy 3D sampled region Angle Weak, isotropic scattering O The hologram (No phase problem!)

4. Inside-Source Holography with Thermal Neutrons Inside-Source Neutron Hologram Al4Ta3O13(OH) O-atom holographic Image-- Centered on H + Bragg peaks Sur et al. Nature 414, 525 (2002)

5. Exciting beamEmitteddetected = source wavewave X-ray Fluorescent x-ray (Gog et al.) Gamma ray/X-ray Conversion e- (nuclear resonance) or gamma ray (Korecki et al.) Neutron Gamma ray (nuclear excitation) (Cser et al.) Direct or Inside-Source Holography Exciting beamEmitted source wave X-ray/Electron Auger electron X-ray Photoelectron X-ray Fluorescent x-ray Electron Incoherently scattered/ Kikuchi electrons Electron Bremsstrahlung x-ray + filter Neutron Incoherently scattered neutrons (from protons) Detector (scanned) Hologram Reference wave Emitted source wave Scattered object/subject waves Exciting beam Emitter = “inside source” Scattering centers: atoms, nuclei Inverse or Inside-Detector Holography Detector (fixed) Exciting beam (scanned) Reference wave Emitted detected wave Emitter = “inside detector” Scattered object/subject waves

6. Inside-Detector Holography with Gamma Rays & Resonant Scattering Images Resonantly scattering nucleus Far-field gamma source e- Horizontal Emitting nucleus Hologram--Fe epitaxial film Vertical Korecki et al. PRL 79, 3518 (1997)

7. Photoelectron and x-ray fluorescence holography: (a) Inside-source holography (direct, XFH): (b) Inside-detector holography (inverse, MEXH): Detector (small solid angle) Object Scattering atom Reference ALS und. beamlines 4.0.2, 7.0.2 hnexcit Exciting x-rays hnfluoror photo-e- Emitting atom ALS b.m. beamlines 9.3.1 11.3.1 superbend? hnexcit Exciting x-rays Scattering atom Object Reference Detector (large solid angle) hnfluor Emitting atom

8. Scattering of x-rays and electrons : X-ray scattering from Ni (+Thomson + resonant effects) |f0()| |0()| Electron scattering from Ni |f()| |()|

9. Inside-source - PH: W 4f7/2 photoelectron spectra surface bulk Two site-specific holograms

10. Inside-source - PH: Len et al. PRB 59, 5857 (1999)

11. surface bulk Images centered on surface W atom Len et al. PRB 59, 5857 (1999)

12. Fe K 3 energies Inside-detector XFH: can be multi-energy “MEXH” Theory Expt. Images of Fe2O3 Gog et al. PRL 76, 3132 (1996)

13. Inside-source XFH: Fe K hologram bcc Fe Symmetrized image 2 energies-K & K Kossel lines e Hiort et al. PRB 61, R830 (2000)

14. Zn K hologram, 9.7 keV Inside-detector XFH: Zn (0.02%) in GaAs Zn K 2-energy image centered on Zn dopant Hayashi et al., PRB 63, 041201 (2001)

15. Some ideas to improve holographic images: Derivative photoelectron holography: Taking differences of intensity to yield logarithmic derivative of I(k), then reintegrate: reduces noise/uncertainty in data (Chiang et al., PRL 81, 4160, (1998))

16. Photoelectron holography: As and Si emission from As/Si(111): Luh, Miller, Chiang, PRL 81, 4160 (1998)

17. Some ideas to improve holographic images: Derivative photoelectron holography: Taking differences of intensity to yield logarithmic derivative of I(k), then reintegrate: reduces noise/uncertainty in data (Chiang et al., PRL 81, 4160, (1998)) Near-node photoelectron holography: Working near the node of the differential cross section: suppresses forward scattering,improves, images (Greber et al., PRL 86, 2337 (2001)).

18. Image around average Al emitter e Near-node photoelectron holography: Al 2s emission from Al(111) Forward scatt. Differential cross section Wider et al. PRL 86, 2337 (2001)

19. Some ideas to improve holographic images: Derivative photoelectron holography: Taking differences of intensity to yield logarithmic derivative of I(k), then reintegrate: reduces noise/uncertainty in data (Chiang et al., PRL 81, 4160, (1998)) Near-node photoelectron holography: Working near the node of the differential cross section: suppresses forward scattering,improves, images (Greber et al., PRL 86, 2337 (2001)). Differential photoelectron holography: Transforming  instead of  : also solves the forward scattering problem (Omori et al., PRL 88, 055504 (2002)).

20. Normal hologram Differential hologram Differential PH (k 0.1 Å-1)  0  0 (Fj = strength of jth scatterer)

23. Some ideas to improve holographic images: Derivative photoelectron holography: Taking differences of intensity to yield logarithmic derivative of I(k), then reintegrate: reduces noise/uncertainty in data (Chiang et al., PRL 81, 4160, (1998)) Near-node photoelectron holography: Working near the node of the differential cross section: suppresses forward scattering,improves, images (Greber et al., PRL 86, 2337 (2001)). Differential photoelectron holography: Transforming  instead of  : also solves the forward scattering problem (Omori et al., PRL 88, 055504 (2002)). Spin-polarized photoelectron holography: Transforming spin-sensitive  instead of  : should permit imaging short-range magnetic order (Kaduwela et al. PRB 50, 9656 (1994))

24. Simulation: MnO-AF cluster Spin-polarized photoelectron holography: direct imaging of magnetic moments in 3D: Normal image- Spin-selective images- Kaduwela et al. , Phys. Rev. B 50, 9656 (1994); Fadley et al., J. Phys. B Cond. Matt. 13, 10517 (2001)

25. Photoelectron holography- • Advantages: • Element-, chemical state-, and spin- specific local structure • Long-range order not required • Large % effects, easy to measure • Surface sensitive, if that’s what you want • Avoids false minima in structure searches • Disadvantages: • Strong scattering leads to multiple scattering (but can be • suppressed by multi-energy datasets) • Not bulk sensitive, if that’s what you want • Future prospects andinstrumentation issues: • --Present status • Detectors not fast enough/linear enough to handle “snapshot” • spectra (cf. ALS project)

26. ALS GHz-RATE 1D DETECTOR 768 channels, 48  spacing, >2 GHz overall Protective shell Microchannel plates 768 collector strips Energy direction Ampl./Discr. (CAFE-M) Counter/ digital readout (BMC) Ceramic substrate Spring clamps for circuit board and MCP cover

27. Photoelectron holography- • Advantages: • Element-, chemical state-, and spin- specific local structure • Long-range order not required • Large % effects, easy to measure • Surface sensitive, if that’s what you want • Avoids false minima in structure optimization • Disadvantages: • Strong scattering leads to multiple scattering (but can be • suppressed by multi-energy datasets) • Not bulk sensitive, if that’s what you want • Requires at least short-range repeated order • Future prospects andinstrumentation issues: • --Present status • Detectors not fast enough/linear enough to handle “snapshot” • spectra (cf. ALS project) • Scanning of sample angles not fast enough • --Future possibilities • Much faster multichannel detectors up to GHz range • Faster scanning of angles via snapshot mode • “Tiling” of hemisphere with analyzers to reduce angle scanning

28. XFH at ESRF: Graphite analyzer Marchesini, Tegze, Faigel et al., Nucl. Inst. & Meth. 457, 601 (2001)

29. X-RAY FLUORESCENCE HOLOGRAPHY AT ESRF--SOME HIGHLIGHTS (Marchesini, Tegze, Faigel et al.) Imaging light atoms:Imaging a quasicrystal: Nature 407, 38 (2000) Phys. Rev. Lett. 85, 4723 (2000)  O around Ni in NiO  method works without true periodicity  ~150 O and Ni atoms imaged  neighbours around Mn in MnAlPd  image of average atomic distribution Ni K Hologram Mn K Hologram Image Image

30. Al.704 Pd.210Mn.086 Quasicrystal First ALS Holograms ESRF--S. Marchesini et al. Phys. Rev. Lett. 85, 4723 (2000) Pd La Mn Ka Hologram • First application of hard x-ray holography to complex system • Structural information in direct space without any assumed model Future data • Environments around both Mn and Pd imaged • Data at many energiesextended range of imaging • More precise atomic environments in the first 5–6 coordination shells, evidence for inflation • Rigorous test of theoretical models Bragg spots Sample edge Reconstruction Mn Ka Samples: P. Thiel P. Canfield

31. 6 1 (a.u.) -6 0 6 Å -6 Å (La, Sr) Mn O X-RAY FLUORESCENCE HOLOGRAPHY AT THE ALS (a) Experimental setup: (Marchesini et al.) • Future plans • •Sample heating/cooling- • phase-transition studies • Applications to: strongly • correlated materials • (CMR high-T phases), • magnetic quasicrystals • (RE-Mg-Zn--I. Fisher), • bio-relevant crystals • •Development of: • -Resonant and • dichroic XFH • -More efficient pixel • detectors High speed motion-acquisition- d/dt = 3600o/sec d/dt = 2o/sec PC Drivers Motion Motion q Clock j Acquisition Acquisition Det Gesolid state det.-- up to 4MHz Monochromatic x-rays ALS (b-e) First data (d) Mn-atom image (scales in Å) MnO (100) CMR: (La,Sr)3Mn2O7 (b) Expt. (c) Calc. (e) Expt. F.T.

32. Jahn-Teller distortions probed with x-ray fluorescence holography: new insights on the CMR effect? La1-xAxMnO3 , A = Ca, Sr , Ca Cubic Orthorhombic LaMnO3 shows long range Jahn-Teller distortions (JT) When x > 0, one theory predicts the coupling of the itinerant electrons with local, short-rangeJT dist. in the T > Tc insulating phase 1.92 2.15 Key to CMR effect? Schematic view of the tetragonal Jahn-Teller distortions in the ab plane

33. Some ideas to improve holographic images: Derivative photoelectron holography: Taking differences of intensity to yield logarithmic derivative of I(k), then reintegrate: reduces noise/uncertainty in data (Chiang et al., PRL 81, 4160, (1998)) Near-node photoelectron holography: Working near the node of the differential cross section: suppresses forward scattering,improves, images (Greber et al., PRL 86, 2337 (2001)). Differential photoelectron holography: Transforming  instead of  : also solves the forward scattering problem (Omori et al., PRL 88, 055504 (2002)). Spin-polarized photoelectron holography: Transforming spin-sensitive  instead of  : should permit imaging short-range magnetic order (Kaduwela et al. PRB 50, 9656 (1994)) Resonant x-ray fluorescence holography: Taking difference holograms above and below a core-level resonance on atom A, and imaging on  again,with weighting wk= +1 below resonance and -1 above resonance, and (below) and (above) calculated at three energies below, on, and above resonance, yields images in which only atom A is prominent.

34. RESONANT X-RAY FLUORESCENCE HOLOGRAPHY: A theoretical study (cf. Van Hove talk) Optical constants for Fe and Ni through the Ni K(1s) edge

35. Normal hologram Differential hologram Differential PH (k 0.1 Å-1)  0  0 Resonant inverse XFH (k 0.01 Å-1) Resonant atom f1+if2 0 Non-resonant atom  0  0

36. Resonant x-ray fluorescence holography (a) (b) MEXH--Fe & Ni (c) RXFH--Fe suppressed Fe1 Ni1 Fe1 Ni1 Ni1 Fe2 Fe2 3.55×2 Å (d) MEXH--Fe & Ni (e) RXFH--Fe suppressed Fe1 Ni1 Ni1 Omori et al., PRB 65, 014106 (2002) Fe2 FeNi3: Structure and simulated holographic images in normal inverse (MEXH) and resonant (RXFH) modes

37. 14 12 10 8 6 4 2 4.8 4.0 4.2 4.4 4.6 Resonant X-Ray Fluorescence Holography Measuring Cd x-ray holograms above and below the Te L3 edge from CdTe Identification of near-neighbour scatterers, ‘true color’ holography. Te L3 Absorption Coefficient (in e-) Photon energy (keV) 1 4 4 3 1 2 4-2=b 1-2=a CdTe structure a b 2 3

38. Some potential applications of x-ray holography: source or detector site source or detector site average source/ detector site average source/ detector site source or detector site source or detector site average source/ detector site Identify via resonant XFH? average source/ detector site Identify via resonant XFH?

39. …and ultimately more dilute species: Active sites in biorelevant molecules source or detector site average source/ detector site source or detector site source or detector site average source/ detector site average source/ detector site

40. X-ray fluorescence holography- Advantages: Element-specific local structure Weak scattering, better holographic imaging Long-range order not required Mosaicity up to few degrees OK Avoids false minima in structure optimization With resonance, near-neighbor identification? With CP radiation, short-range magnetic order imaging? Disadvantages: Small % effects, need approx. 109-1010 counts in hologram Requires at least short-range repeated order

41. X-ray fluorescence holography- • Future prospects andinstrumentation issues: • --Present status • Detector-limited--e.g.,graphite crystal plus avalanche photodiode (ESRF); Ge detectors up to 1 MHz over 4 elements (LBNL)hologram in approx. 1-10 hours • --Future possibilities • "Tiling" of hemisphere with Ge detectors ala Gammasphere, Si drift diodes (HASYLAB, Materlik et al.?, commercial sources Ketek and Photon Imaging?) • --Future “dream machine” • 1 angular resolution, 100 eV resolution for x-rays at 6-20 keV, hemisphere coverage, 1-100 GHz overallhologram in 0.1-10 sec, or in one LCLS pulse

42. E.g., the LBNL Gammasphere: Why not! 110 large volume, high-purity germanium detectors

43. The End