X-Ray Microscopy with Elemental, Chemical, and Structural Contrast

Transcription

1 Institut für Strukturphysik, TU Dresden, Christian Schroer X-Ray Microscopy with Elemental, Chemical, and Structural Contrast Christian G. Schroer Institute of Structural Physics, Technische Universität Dresden D Dresden

2 Collaboration P. Boye, J. Feldkamp, A. Goldschmidt, R. Hoppe, J. Patommel, D. Samberg A. Schropp, A. Schwab, S. Stephan Inst. of Structural Physics, TU Dresden M. Burghammer, C. Riekel, S. Schöder, P. Glatzel ESRF, Grenoble G. Falkenberg, N. Reimers, I. Vartaniants, E. Weckert HASYLAB, DESY, Hamburg B. Lengeler II. Phys. Institut, RWTH Aachen J.-D. Grunwaldt Danish Technical University B. Kimmerle, A. Baiker ETH Zürich W. H. Schröder FZ Jülich... Zakopane School of Physics 2

3 Hard X-Ray Microscopy Hard x-rays: large penetration depth: inner structure of sample (also in-situ) short wave length: structure determination down to atomic level energy range: spectroscopy (fluorescence & absorption) chemical and structural information from inside a sample! Full-field microscopy: transmission image efficient parallel data acquisition transmission contrasts: absorption (including XAS) phase contrasts (various kinds) tomography: local inner structure of sample Zakopane School of Physics 3

4 Hard X-Ray Microscopy Hard x-rays: large penetration depth: inner structure of sample (also in-situ) short wave length: structure determination down to atomic level energy range: spectroscopy (fluorescence & absorption) chemical and structural information from inside a sample! Scanning microscopy: scan sample with focused beam different contrasts: fluorescence absorption (XAS) diffraction (SAXS & WAXS, CXDI)... tomography: local inner structure of sample K Zakopane School of Physics 4

5 High brilliance: ERL High flux per phase space volume Ideal for nanobeams small source: small geometric image (diffraction limited focusing) small divergence: optic captures large fraction of emitted radiation Zakopane School of Physics 5

6 Synchrotron Radiation Sources PETRA III at DESY: lowest emittance highest brilliance User operation will start 2010 ESRF: currently: most brilliant source in Europe over 6500 user visits/year Zakopane School of Physics 6

7 Full-Field Tomography reconstructing the 3D structure from large number of projections example: Mahogani root 1250 projections: 400µm reconstruction of single slices Zakopane School of Physics 7

8 Full-Field Tomography reconstruction: single slice example: Mahogani root filtered back projection 400µm resolution: ~ 3 µm Zakopane School of Physics 8

9 Full-Field Tomography reconstruction: 3D structure example: Mahogani root single slice volume data set 400µm resolution: ~ 3 µm Zakopane School of Physics 9

10 Looking at Catalysis Grunwaldt, et al., J. Chem. Phys. B 110, 8674 (2006) Zakopane School of Physics 10

11 Looking at Catalysis Combustion of methane: CH 4 + 2O 2 CO 2 + 2H 2 O (exothermal: -801,7kJ/mol) reforming methane to H 2 : Rh CH 4 + H 2 O CO + 3H 2 (endothermal: 206.1kJ/mol) Rh CH 4 + CO 2 2CO + 2H 2 (endothermal: 247,5kJ/mol) Grunwaldt, et al., J. Chem. Phys. B 110, 8674 (2006) alternative reaction: partial oxidation: 2CH 4 + O 2 (exothermal: -35,5kJ/mol) Zakopane School of Physics 11 2CO + 8H 2

12 Looking at Catalysis Imaging the catalytic reactor in transmission Rh K-edge Zakopane School of Physics 12

13 Looking at Catalysis Rh 3+ Rh Rh Rh 3+ Zakopane School of Physics 13

14 Looking at Catalysis gas flow Rh 3+ Rh combustion reforming Detailed Study: S. Hannemann, et al., Catalysis Today 126, (2006). Zakopane School of Physics 14

15 Space- and Time-Resolved XAS: Filming a Catalyst in Action same reaction but different catalyst L3-edge of Pt Zakopane School of Physics 15

16 Space- and Time-Resolved XAS: Filming a Catalyst in Action before ignition: Pt oxidized (pronounced white line) reforming ignites at end of reactor and moves toward the inlet Pt reduced! Δt = 0.25 s B. Kimmerle, et al., J. Chem. C, 113, 3037 (2009) inlet Zakopane School of Physics end (outlet) 16

17 Hard X-Ray Scanning Microscopy source L 1 Focus size and shape determined by: source size magnification L 2 /L 1 diffraction limit aberrations lens Flux in focus determined by: brilliance source size L 2 = L 1f L 1 f microbeam on sample focusing cross-section of lens Zakopane School of Physics 17

18 XANES-Microtomography Probe chemical state of a given element on virtual section through the sample Sample: CuO/ZnO-catalyst + BN powder in glass capillary (chem. reactor) virtual section Zakopane School of Physics 18 J.-D. Grunwaldt, A. Baiker, ETH Zürich

19 XANES-Microtomography Probe chemical state of a given element on virtual section through the sample Sample: CuO/ZnO-catalyst + BN powder in glass capillary (chem. reactor) virtual section determine absorption spectrum at each location on virtual slice Zakopane School of Physics 18 J.-D. Grunwaldt, A. Baiker, ETH Zürich

20 XANES-Microtomography Schroer, et al., Applied Physics Letters 82, 3360 (2003) Zakopane School of Physics 19

21 XANES-Microtomography QEXAFS-monochromator (R. Frahm et al., Wuppertal) data acquisition: signals from ionization chambers and PINdiode are recorded at a rate of 10kHz to 100kHz synchronization with cam-driven oscillating monochromator In this experiment: 10 full oscillations/s (20 spectra/s) 10 4 points per spectrum Zakopane School of Physics 20

22 XANES-Microtomography x-rays optic I0 rotation reference translation sample I1 I2 Zakopane School of Physics 21

23 XANES-Tomographic Data Set 102 projections 91 positions per projection At each position of the scan rotation 10 spectra in 1 second sampling rate: 100kHz translation more than spectra with 10 4 data points each: > 7GByte raw data near edge spectrum (XANES) Zakopane School of Physics 22

24 XANES-Tomographic Data Set 102 projections 91 positions per projection At each position of the scan rotation 10 spectra in 1 second sampling rate: 100kHz translation more than spectra with 10 4 data points each: > 7GByte raw data near edge spectrum (XANES) Zakopane School of Physics 23

25 Tomographic Reconstruction Independent reconstruction for each energy below Cu K-edge reconstructed and reference spectra 200µm above Cu K-edge (4) (1) (3) (2) (5) (6) µ [a.u.] Zakopane School of Physics 24

26 Distribution of Chemical Compounds Cu (metallic) Cu(I) 2 O difference 200µm - = Cu(II)O other elements µ [a.u.] Zakopane School of Physics 25 APL 82, 3360 (2003)

27 Scanning Microscopy: Fluorescence Tomography fluorescence: element distribution Cl K 200µm Ca Rb APL 79, 1912 (2001) Mahogani root Zakopane School of Physics 26

28 Scanning Microscopy: SAXS-Tomography Probe nanoscale structure on a virtual section through a sample Sample: nondestructive probe of the interior of sample define virtual slice obtain SAXS cross section at each location on section APL 88, (2006) injection molded PE Collab.: N. Stribeck, Univ. Hamburg Zakopane School of Physics 27

29 SAXS-Tomography I q (r) 101 projections with 70 steps each 80µm step size Zakopane School of Physics 28

30 SAXS-Tomography Reconstruction: attenuation diffraction integral scattering along rotation axis q r = 0 Zakopane School of Physics 29

31 SAXS-Tomography Sample is fibre textured: scattering cross section scattering cross section inhomogeneous nanostructure In each pixel: full scattering cross section (rotationally symmetric) APL 88, (2006) Zakopane School of Physics 30 interpretation: Stribeck, et al. Macromol. Chem. Phys. 207, 1139 (2006)

32 Refractive X-Ray Optics first realized in 1996 (Snigirev et al.) a variety of refractive lenses have been developed since applied in full field imaging and scanning microscopy most important to achieve optimal performance: aspherical lens shape parabolic Zakopane School of Physics 31

33 Refractive X-Ray Lenses Many different realizations, e. g.: Nanofocusing lenses Rotationally parabolic lenses imaging Zakopane School of Physics µm Short focal length: large demagnification small image large numerical aperture small diffraction limit

34 Parabolic Refractive X-Ray Lenses Bruno Lengeler RWTH Aachen Zakopane School of Physics 33

35 Parabolic Refractive X-Ray Lenses Bruno Lengeler RWTH Aachen Zakopane School of Physics 33

36 Magnified Imaging: Full-Field Microscopy lenses used as objective in full-field microscope image distance L 2 = L 1f L 1 f numerical aperture NA = D eff 2L Zakopane School of Physics 34

37 Full-Field Imaging Ni-mesh (2000mesh) Parabolic profile of lenses is crucial to good image quality imaging parameters: E = 12keV N = 91 (Be) f = 495 mm m = 10x 25µm spatial resolution: ~ 100 nm Zakopane School of Physics 35

38 Rotationally Parabolic Refractive X-Ray Lenses Two applications at micro-/nanoprobe beamline: Prefocusing: prefocusing optic (adaptable) unfocused cone lt (unfocused) microscope lt secondary source Micro -focusing at ESRF ID10: E = 8 kev L1 = 60.8 m f = 156 mm gain ~ 10 5 flux: ph/s mono: Si 111 Zakopane School of Physics I [a.u.] 200nm pos PETRA III (expected): E = 8 kev L1 = 88 m f = 156 mm gain ~ x 190 nm 2 36

39 Nanofocusing Lenses (NFLs) nanolens strong lens curvature: R = 1µm - 5µm N = optical axis single lens 100 µm lens made of Si by lithography and deep reactive ion etching! Zakopane School of Physics APL 82, 1485 (2003) 37

40 Fabrication of Si Nanofocusing Lenses Over 4700 lens arrays Over structures high accuracy, reproducibility Zakopane School of Physics 38

41 Crossed Nanofocusing Lenses Setup at ID13 of ESRF Zakopane School of Physics 39

42 Crossed Nanofocusing Lenses Setup at ID13 of ESRF aperture defining pinhole sample vertically focusing lens horizontally focusing lens 10mm Zakopane School of Physics 39

43 Focusing with NFLs Si lens: E = 21keV, L 1 = 47m source: ID13 low-β invac. undulator horizontal focus: 47nm f = 10.7mm source size: 150 x 60µm 2 vertical focus: 55nm f = 19.4mm demagnification: ~ 2400 x 4400 flux: ph/s APL 87, (2005) Zakopane School of Physics 40

44 Effective Aperture and Diffraction Limit Diffraction limit: N = 100 l R = µm first diamond lens Best materials: high density and low Z Zakopane School of Physics 41

45 Nanoprobe: Coherent X-Ray Diffraction Imaging (CXDI) sample beamstop E = kev λ = Å beam size: < 150 x 150 nm 2 (amplitude) Zakopane School of Physics 42

46 Test Object: Gold Particle on Si3N4-Membrane particle under investigation size < 100 nm Zakopane School of Physics 43

47 Diffraction Pattern of Gold Nanoparticle sample-detector distance: 1250 mm (in air) detector: FReLoN 4K 50µm pixel size exposure time: 10 x 60 s intensity on sample: 2500 ph/s/nm 2 Zakopane School of Physics 44

48 Reconstruction reconstruction by HIO shrink-wrap phase left free to evolve 200 reconstructions (9 converged to wrong solutions) reconstructions: left-handed right-handed Zakopane School of Physics PRL 101, (2008) 45

49 Reconstruction reconstruction by HIO shrink-wrap phase left free to evolve 200 reconstructions (9 converged to wrong solutions) reconstructions: left-handed right-handed Zakopane School of Physics PRL 101, (2008) 45

50 Reconstruction reconstruction by HIO shrink-wrap phase left free to evolve 200 reconstructions (9 converged to wrong solutions) reconstructions: left-handed right-handed averaged solution: 100nm Zakopane School of Physics PRL 101, (2008) 45

51 Reconstruction reconstruction by HIO shrink-wrap phase left free to evolve 200 reconstructions (9 converged to wrong solutions) reconstructions: left-handed right-handed averaged solution: resolution: < 5 nm 100nm Zakopane School of Physics PRL 101, (2008) 45

52 Scanning Microscope at PETRA III: beamline P06 BL responsible: G. Falkenberg nanoprobe built by TU Dresden (available 2010) microprobe nanoprobe Zakopane School of Physics 46