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XX--ray Microscopy 2002ray Microscopy 2002July 29 July 29 –– August 2, 2002,August 2, 2002, GrenobleGrenoble, France, France

Main Organizer: Jean Main Organizer: Jean Susini Susini (ESRF)(ESRF)

•• Oral & poster presentationsOral & poster presentations•• 239 registrants239 registrants•• 49 PhDs49 PhDs•• Visit to ESRFVisit to ESRF•• Dinner at Chateau Dinner at Chateau d’Herbelond’Herbelon

Highlights of XRM'02Highlights of XRM'02

•• Novel opticsNovel optics•• Phase contrastPhase contrast•• More hard xMore hard x--rays rays •• Lots of applications … Lots of applications …

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Background on XBackground on X--ray Microscopyray Microscopy

ESRF ID21: TXMTXM 3-6 keV ESRF ID21: SXMSXM 2-10 keV & < 2keV

⇒ transmission⇒ fluorescence⇒ XPEEM

• Two types: full field & scanning

• All types of materials are studied, from biological to magnetic

• Increasing number of SR imaging microscopes worldwide due to availability of => high-resolution lens-like optics: zone plates, KB mirrors, CRLs=> high-brilliance synchrotron sources

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Nanofabricated Diffractive OpticsNanofabricated Diffractive Optics

Linear zone plates: C. David (PSI)

Multilevel zone plates: Fabrizio (Elettra) & David (PSI)

Complex zone plates: Di Fabrizio (Elettra)Wilhein (Remagen, Germany)

Photon sieves: P. Charalambous (King’s College)

1D & 2D wave guides: T. Salditt (U. Saarbrucken)

Diamond refractive lenses: A. Freund (ESRF)

68.7nm x 33.0nm (derived)

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Linear zone platesLinear zone plates::C. David (PSI)

⇒ Matching anisotropic source shape & size

⇒ Tilted to increase ZP’s efficiency

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Multilevel Zone PlatesMultilevel Zone Plates::C. David (PSI)

Di Fabrizio, Nature (1999)

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Photon SievesPhoton Sieves::P. Charalambous (King’s College)

L. Kipp et al., Nature (2001)

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Complex zone platesComplex zone plates:: Di Fabrizio (Elettra)Wilhein (Remagen, Germany)

2 spots

4 spots

⇒⇒ Multiple focal spots in single or Multiple focal spots in single or multiple focal plane for differential multiple focal plane for differential interference contrast microscopyinterference contrast microscopy

⇒⇒ Complete beam shaping for Complete beam shaping for masklessmaskless lithography & xlithography & x--ray ray induced CVD

2 spots longitudinal

induced CVD

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Differential InterferenceDifferential InterferencePhase Contrast with ZP DoubletPhase Contrast with ZP Doublet

Wilhein et al. APL 78, 2082 (2001).ESRF, ID21, 4 keV

PMMA 2µm-thick: 98.7% transmission

Giant moss spores of Dawsonia superba

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XX--ray Shearing Interferometerray Shearing Interferometer::C. David (PSI)

Calculation

ExperimentSi phase grating beam splitter

polystyrene spheres of 0.1mm and 0.2mm

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Some Examples on ApplicationsSome Examples on Applications

Nano-tomography on AMD K6: C.G. Schroer (Aachen) A. Snigirev (ESRF)

Magnetic imaging with XMCD: P. Fischer (MPI, Stuttgart)G. Denbeaux (ALS)

3D XRD mapping of grains: H. Poulsen (Riso)B. Larson (ORNL) @ IUCr

Element mapping in biological samples: C.G. Schroer (Aachen)A. Snigirev (ESRF)

Spectromicroscopy of polymers: A.P. Hitchcock (McMaster)

Cryo tomography soft x-rays: C.A. Larabell (Anatomy, UCSF)

Many many more ……

Yeast: single celled eukaryotic organism, ~5µm in diameter

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NanoNano--tomography tomography on AMD K6on AMD K6::

C.G. Schroer (Aachen) A. Snigirev (ESRF)

ID22 ESRF:

parabolic Al refractive lensimaging onto 2D detectorx-ray energy 25 keVmagnification 20.9x 3D resolution 410nm

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Fluorescence Fluorescence Microtomography Microtomography with Microwith Micro--beambeam::

C.G. Schroer (Aachen) A. Snigirev (ESRF)

Specimen:

mycorrhyzal root of tomato plant, grown on heavy metal polluted soil

ID22 ESRF:

parabolic Al refractive lensfocal spot: 3 µm x 0.9 µm scan step: 1 µm 132 projections in 360o

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Full Field Fluorescence MicroscopeFull Field Fluorescence MicroscopeOhigashi, Watanabe, Yokosuka & Aoki, JSR 9, 128 (2002).

1Kx1K CCD: 12µm x 12µm pixels, photon counting => 210eV @8keV

10:1 magnificationPt-coated Pyrex

Fe Co Ni Cu

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Full field magnetic imaging with XMCD:

P. Fischer, G. Schutz (MPI, Stuttgart)G. Denbeaux, D. Attwood (ALS)

Full field magnetic imaging with XMCD

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Fe L3 & L2⇒ No polarity switching necessary

⇒ Contrast reversal between L3 & L2

⇒ Compared to EM: no effects from applied H

Fe 4A / Gd 4A x75

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Magnetic Nanostructures Magnetic Nanostructures

Eimuller et al. Appl. Phys. A (2001)

Landau patterns

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Eimuller et al. Appl. Phys. A (2001)

Fe/Gd 190nm dots

In-plane domains

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Imaging Magnetic ‘Bits’ in MagnetoImaging Magnetic ‘Bits’ in Magneto--optical Film optical Film

Fischer et al. JSR (2001)

ThermomagneticThermomagnetic recording by laserrecording by laser--pumped magnetic pumped magnetic field modulation field modulation

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Undulation Instability in Magnetic Undulation Instability in Magnetic Nanowires Nanowires Eimuller et al. JAP (2002)

Multilayer:

(4A Fe/4A Gd)x75on 300nm Si3N48nm Al cap layer

E-beam lithography:

2µm to 100nm lines

H

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Spin dynamics Spin dynamics on on nanostructurednanostructured magnetsmagnets

with pumpwith pump--probe probe

Deneaux et al. XRM (2002)

⇒ micro-coil with pulser (rise time ~100ps)

⇒ x-ray pulse from ALS (Fwhm<70ps, 3MHz)

⇒ pump-probe delay (0 < ∆t < 328ns)

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Highlights on Phase ContrastHighlights on Phase Contrast

Zernike phase contrast: Y. Kagoshima (Spring-8)U. Neuhausler (ESRF)

Phase contrast in STXM: M. Feser (SUNY-SB)G. Morrison (Kings College)

Differential phase contrast: T. Wilhein (U. Koblenz, Germany)

Phase contrast tomography: P. Cloetens, J. Baruchel (ESRF)

Shearing interferometry: C. David (PSI)

Diffraction microscopy: J. Miao (SSRL)M. Howells (LBNL)J. Kirz & D. Sayre (SUNY-SB)

Nanocrystal diffraction imaging: I. Robinson (UIUC) @ IUCr

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Absorption ContrastAbsorption Contrastvs. Phase Contrastvs. Phase Contrast

• Phase contrast is x104 higher than absorption contrast for protein in water @ 8keV

Phase contrast(with Ta phase plate)

Absorption contrast

• Dose reduced to level comparable to using water-window in soft x-ray region

C94H139N24O31S

1010

108

106

104

103102 104

Kirz (1995): 0.05µm protein in 10µm thick ice

X-ray Energy (eV)

Dos

e (G

ray)

absorption contrast

phase contrast

Refraction index: n = 1 − δ − iβ

absorption contrast: µz = 4πβz/λ ∼ λ 3

phase contrast: φ(z) = 2πδz/λ ∼ λz

Kagoshima et al. (2001): protein C94H139N24O31Sρ=1.35g/cm3, t=0.1µm in 10µm water

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Principle ofPrinciple of ZernikeZernike Phase ContrastPhase Contrast(Born & Wolf)(Born & Wolf)

For pure phase object: F(x) = e iφ(x) ~ 1 + iφ(x)

=> No absorption contrast: |F|2 ~ 1

=> F'(x) ~ ±i + iφ(x) => Phase contrast: |F'|2 ~ 1 ± 2φ(x)

phase plate: ∆φ=±π/2 in zeroth-order

Zernike method in visible optics:

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ZernikeZernike Phase ContrastPhase Contrastfor xfor x--raysrays

Soft X-rays: Schmahl et al. (1995). BESSY, 0.5 keV.

Hard X-rays: Kagoshima et al. (2001). SPring8, 10keV.

3-5 minutes exposures at SPring-8 undulator BL24XU

Conidium of Curvularia species

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ZernikeZernike Phase ContrastPhase ContrastMore recent: Kagoshima et al. JSR 9, 132 (2002).

SPring-8 BL24XU

Cu mesh Polystyrene spheres D=7µm

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Phase Contrast in STXMPhase Contrast in STXM M. Feser, C. Jacobsen, XRM (2002).

M. Feser: recipient of Meyer-Ilse Award on XRM (2002).

pin-diode

⇒ Multi-segment detector

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M. Feser (2002).

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Phase Contrast in STXM with CCDPhase Contrast in STXM with CCDG. Morrison (King’s College)

SoftwareSoftware--configurable CCDconfigurable CCD::

!! absorptionabsorption!! phase contrastphase contrast!! dark fielddark field

=> simultaneous detection=> simultaneous detectionof both of both δδ and and ββ on the on the same sample areasame sample areamulti-element 80x80 CCD

3 x-rays/pixel@ 3keV uncooled

Phase contrast modesPhase contrast modes::

!! 11stst momentmoment

!! 11stst momentmoment

!! measures phase gradientmeasures phase gradient

),( iii yxIxx ∑ ⋅=

),( iii yxIyy ∑ ⋅=TXMTXM

TXM and STXMTXM and STXM::

!! related by related by optical reciprocityoptical reciprocity!! detector in STXM detector in STXM "" extended source in TXM

STXMSTXM

extended source in TXM

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M. Feser, Ph.D Thesis (2002).

⇒ phase-contrast below C K-edge for biological specimens?

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Phase Retrieval in PhasePhase Retrieval in Phase--Contrast ImagingContrast Imaging

Phase Retrieval: I(u, v) # ρ(x, y) = ?

Propagation based method:

Teague, J. Opt. Soc. Am. 4, 118 (1987) Gureyev et al., J. Opt. Soc. Am. 12, 1942 (1995)Nugent et al., PRL 77, 2961 (1996)Paganin & Nugent, PRL 80, 2586 (1998)

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$ Phase is defined by: (i) index of refraction n(r)

n = 1 – δ + i β k = n k0 eikz ~ k0∫ n(x,y,z) dz

(ii) energy flow S(r)

E = E(r) eik⋅r = E(r) eiφ(r) ∇ φ = ∇ (k⋅r) = k = propagation direction

$ Transport of intensity equation

Poynting vector: S(r) ~ |E|2 k ~ I ∇ φ

Energy conservation: ∇⋅ S = 0

=> ∇ ⋅ (I ∇ φ) = 0

# Solution of φ from intensity I(r)

zk0

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Phase Imaging & TomographyPhase Imaging & Tomography

λ

Cloetens et al. (1999): ESRF, ID19, 18 keVPolystyrene foam 0.7x0.5x1mm3

1.4T wiggler, B~7x1014 ph/s/mr2/mm2/0.1% @100mA4x700 images at 25 sec/image

• A form of Gabor in-line holography• Coherence over 1st Fresnel zone (λR)1/2

• Image reconstruction (phase retrieval)• Spatial resolution limited by pixel size

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Phase Contrast Phase Contrast Microscopy by DefocusingMicroscopy by Defocusing

Allman et al. JOSA (2000). APS, 2-ID-B, 1.8 keV

holographic geometry

spider silk fiber: φ1.7µm

imaging geometry

retrieved phase: 2.5 rad

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Diffraction MicroscopyDiffraction Microscopy

• Spatial resolution: essentially no limit.(only limited by ∆λ/λ and weak signals at large angles)

• Key development: oversampling phasing methodcoherent flux!!

• Coherent diffraction from noncrystalline specimen:=> continuous Fourier transform

• Diffraction microscopy is analogous to crystallography, but for noncrystalline materials

• Coherence requirement: coherent illumination of sample

Coherent X-rays

Miao et al. (1999) >>>soft x-rays, reconstruction to 75 nm

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Diffraction MicroscopyDiffraction Microscopymost recent resultsmost recent results

reconstructed image: to d~7nm resolution

Miao et al. (2002) λ = 2 Å

Gold: 2.5µm x 2µm x 0.1µm

SPring-8 undulator BL29XU: standard 140 periods λu=3.2 cmB=2x1019 ph/s/mr2/mm2/0.1% @100mAFor Au, exposure time 50 min, d~7nmBut: for C, (Zc/ZAu)2~1/173 => 6 days!!

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3D Structures3D Structureswith Coherent Diffractionwith Coherent Diffraction

λ=2Å Coherent diffraction microscopy: Miao et al. (2002).

Two nickel plates: 2.8x2.6x1.2µm3

SPring-8, BL29XU

Reconstructed to 55nm resolution in 3D, based on 30 frames in 5o steps, 20 min/frame, ~10hrs.

⇒ Single molecule imaging ??

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More Phase Contrast … …More Phase Contrast … …

•• Coherent Coherent nanocrystalsnanocrystals diffractiondiffraction•• Fourier Transform HolographyFourier Transform HolographyRobinson et al. (2001): 1µm Au nanocrystal

Leitenberger & Snigirev (2001)

Au (111)

• Imaging of shape and strain innanocrystals

• particle-size broadened Bragg peaks help solving phase problemdue to oversampling

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Vartanyants & Robinson J. Phys.: Cond. Matter

13, 10593 (2001).

Partial coherence=> small areas of high intensitied in reconstructed images

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Model Free Model Free Strain Profile ?Strain Profile ?

Shen & Kycia (1997)PRB 55, 15791.

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ERL Spatial CoherenceERL Spatial Coherence

ERL emittance (0.015nm)ESRF emittance(4nm x 0.01nm)

Cornell ERLCornell ERL: diffraction: diffraction--limited source limited source E < 6.6 E < 6.6 keVkeValmostalmost diffractiondiffraction--limited tolimited to 13 13 keVkeV

Diffraction limited @ 8keV

Diffraction limited source: 2πσ'σ = λ/2 or ε = λ/4π

Almost diffraction limited: 2πσ'σ ~ λ or ε ~ λ/2π

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Spatial CoherenceSpatial Coherence−− a few definitionsa few definitions

2σ 2σ' • 2σ ~ λ

σ'2σ' 2σ

∆l = σ' • 2σ = λ/2

X-ray beam is spatially coherentif phase-space area 2πσ’σ < λ/2

=>

Diffraction limited source: 2πσ'σ = λ/2 or ε = λ/4π

Almost diffraction limited: 2πσ'σ ~ λ or ε ~ λ/2π

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SourceSource EmittanceEmittance and Brillianceand Brilliance

xx’

Integrated total flux Fn

⇒ PhasePhase--space space EmittanceEmittance::

EM wave: E(r, t) = E0 ei(k·r−ωt)

t

E

στ

σE

ετ = στ σE / E

y

y’

σy

σy’

εy = σy σy’

x

x’

σx

σx’

εx = σx σx’

⇒ BrillianceBrilliance: photon flux density in phase: photon flux density in phase--spacespace

B =Fn

(2π)3 εx ·εy·ετ

^PeakB =Fn

(2π)2 εx ·εyAverage

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Benefits of ERL to XRMBenefits of ERL to XRM

⇒ Brings high coherence to hard x-ray regime

⇒ Better optical performance for STXM & µ-probe

⇒ Phase imaging & microscopy

⇒ Far-field diffraction microscopy

⇒ Holographic techniques

⇒ Time-resolved and flash microscopy

⇒ Larger depth of focus for tomography & 3D structures

⇒ Coherent Crystallography, etc.

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MicroMicro--focusingfocusing

Sigma x Sigma x’ Sigma y Sigma y’(µm) (µr) (µm) (µr)

ESRF Microfocus BL 57 88.5 10.3 7.2

Advanced Photon Source 359 24 21 6.9

Energy Recovery Linac 24.5 6.1 24.5 6.10.15 nm, 100 mA, 25 m IDEnergy Recovery Linac 3.9 4.7 3.9 4.70.015 nm, 10 mA, 2 m ID

D1 D2

Bilderback (2000)ERL Workshop

⇒ Require slope error δθ << σx / D1 = 3.9 µm / 40 m = 0.1 µrad

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High Resolution XHigh Resolution X--ray Microscopy ?ray Microscopy ?

TEM like TEM like microscropymicroscropy for hard Xfor hard X--raysrays? ?

object plane back focal plane image plane

Thin crystal

• Would it be possible to image atomic planes (atoms) in a crystal thin enough for x-rays?

• TEM without sample preparation !!!

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•• XX--ray microscopy is an exciting field due to ray microscopy is an exciting field due to advances in focusing optics, 2D detectors, better advances in focusing optics, 2D detectors, better sources, precise mechanics, & phasing algorithmssources, precise mechanics, & phasing algorithms

SummarySummary

•• Lots of ‘old’ ideas for TEM and optical Lots of ‘old’ ideas for TEM and optical microscope are now being tested and applied microscope are now being tested and applied for hard xfor hard x--raysrays

•• Lots of application possibilities … Lots of application possibilities …

•• CHESS can make substantial contributions due CHESS can make substantial contributions due to our existing interests in optics, detectors, ERL, to our existing interests in optics, detectors, ERL, xx--ray physics, phasing methods, & nanofabricationray physics, phasing methods, & nanofabrication

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XX--ray Microscopy 2002ray Microscopy 2002

interferencestationarysplitInterferometerscatteredstationarycoherentDiffraction

transmitted, fluorescence, or refracted

scannedfocusedScanning Probe

transmitted, refracted

stationaryplane or spherical wave

ImagingtransmittedstationarycondensedMicroscope

Detected beam

sampleIncident beam