holographic imaging of atomic structure: where is it and where can it go? c.s. fadley

Holographic Imaging of Atomic Structure: Where Is It and Where Can It Go?

C.S. FadleyUC 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 BiosciencesV.K. Yachandra,T.N. Earnest, LBNL Physical Biosciences

M. Tegze, G. Faigel--BudapestM. Belakhovsky--Grenoble, ESRF

J. Garcia de Abajo--San Sebastian (theory)

Exciting beam

Emitter = “inside source”

Hologram

Scattered object/subject waves

Reference waveEmitted

source wave

Scattering centers: atoms, nuclei

Direct or Inside-Source Holography

Inverse or Inside-Detector Holography

Refer

ence

wave

Detector(fixed)


Emitter = “inside detector”

Exciti

ng bea

m

(sca

nned)

Emitted detected wave

Exciting beam Emitted detected = source wave wave

X-ray Fluorescent x-ray

Gamma ray/X-ray Conversion e-

(nuclear resonance) or gamma ray

Neutron Gamma ray(nuclear excitation)

Detector (scanned) Exciting beam Emitted 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.)

The basic imaging ideas:(Gabor; Helmholtz-Kirchoff; Wolf; Szöke; Barton-Tong)

2

ref obj

2 2*ref ref obj ref obj obj

2

ref02

0ref

23

*

I( k ) Φ ( k ) Φ ( k )

Φ ( k ) Φ ( k )Φ ( k ) Φ ( k )Φ ( k ) Φ ( k )

I( k ) Φ ( k )I( k ) IHo log ram : χ( k )

I Φ ( k )Ho log raphic image :

U( r ) χ( k )exp[ ik r ikr ]d k

k I( k )

O

3D sampled region

Weak,isotropicscattering

The hologram

Energy

An

gle

(No phase problem!)

Inside-SourceNeutron Hologram

Al4Ta3O13(OH)

O-atom holographic Image--Centered on H

Sur et al. Nature414, 525 (2002)

Inside-Source Holographywith Thermal Neutrons

ΔI0.5%

I

+ Bragg peaks

Exciting beam

Emitter = “inside source”

Hologram


Reference waveEmitted

source wave

Scattering centers: atoms, nuclei

Direct or Inside-Source Holography

Inverse or Inside-Detector Holography

Refer

ence

wave

Detector(fixed)


Emitter = “inside detector”

Exciti

ng bea

m

(sca

nned)

Emitted detected wave

Detector (scanned) Exciting beam Emitted 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)

Exciting beam Emitted detected = source wave wave

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.)

Inside-Detector Holographywith Gamma Rays & Resonant Scattering

Korecki et al. PRL79, 3518 (1997)

ΔI2%

I

Hologram--Fe epitaxial film

Images

Resonantlyscatteringnucleus

Emittingnucleus

Far-fieldgammasource

Horizontal

Vertical

e-

Photoelectron and x-ray fluorescence holography:

(a) Inside-source holography (direct, XFH):

(b) Inside-detector holography (inverse, MEXH):

Emitting atom

Scatteringatom

Exciting x-rays

Object

Reference

Emitting atom

Scatteringatom

Detector(large solid

angle)

Excitingx-rays

Object

Reference

h fluoror

photo-e-

hexcit

Detector(small solid

angle)

hexcit

hfluor

ALS b.m. beamlines 9.3.1 11.3.1superbend?

ALS und.beamlines 4.0.2, 7.0.2

Scattering of x-rays and electrons :

Electron scattering from Ni

|f0()|

|f()|

|0()|

|()|

X-ray scattering from Ni (+Thomson + resonant effects)

Inside-source - PH:W 4f7/2 photoelectron spectra

bu

lk

surf

ace

Two site-specific holograms

Inside-source - PH:

Len et al. PRB59, 5857 (1999)

Images centered on surface W atom

bu

lk

surf

a ce

Len et al. PRB59, 5857 (1999)

Imagesof Fe2O3

Gog et al. PRL76, 3132 (1996)

Expt. TheoryΔI0.5 %

I

Fe K

3 energies

Inside-detector XFH: can be multi-energy“MEXH”

Inside-source XFH:

Fe K hologram

Kossel lines

bcc FeSymmetrized image2 energies-K & K

Hiort et al. PRB61, R830 (2000)

ΔI0.3 0.5 %

I e

Inside-detector XFH:Zn (0.02%) in GaAs

Zn K

Zn K hologram, 9.7 keV

2-energyimage

centered on Zn dopant

Hayashi et al., PRB 63, 041201 (2001)

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))

Photoelectron holography:As and Si emission fromAs/Si(111):

23

0

0

3

U( r ) χ( k )exp[ ik r ikr ]d k

I( k ) Iˆwith χ

I

and I( k ) from int egration of log arithmic

derivative

ˆ Î( hν δ,k ) I( hν δ,k )ˆL( hν ,k ) ,ˆ Î( hν δ,k ) I( hν δ,k ) δ

ˆ Î( k ) I( k ,k ) A L( hv ,k )d k

Luh, Miller, Chiang, PRL81, 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)).

Forwardscatt.

Differentialcross section

Near-node photoelectronholography:Al 2s emission fromAl(111)

Wider et al. PRL86, 2337 (2001)

Image aroundaverage Al emitter

e




Differential photoelectron holography: Transforming instead of : also solves the forward scattering problem (Omori et al., PRL 88, 055504 (2002)).

Differential PH (k 0.1 Å-1) 0 0

2kkk

..]exp[ cciikrFj

jjj rkk

..expeff ccriikrF

jjjj

kk

kkk

jjjjjjj ir

kiFir

kiFF rkkrkk ˆ

2sin2ˆ

2expeff

Normal hologram

Differential hologram

(Fj = strength of jth scatterer)

Diff erential photoelectron holography: normal and eff ective scattering factors for Cu

(a) k=4.6Å-1 (81eV), k = 0.2Å-1 (E = 7 eV)

f

efff

=0o180o

fwd.back

(b) k=8.8Å-1 (295eV), k = 1.0Å-1 (E = 67eV)

f

efff

=0o180o

fwd.back

12

3

4

6

e

A

2’

4’

6

4emitter

4’

3

21

2’

Cu 3p-Cu(001)- -diff erentialholography

[100] x (Å) [010] y (Å)

[001

] z (Å

)

Diff erential photoelectron holography: imaging of back, side, (and fwd.) scattering atoms

(Omori et al., PRL 88, 055504 (’02) andanimations at http:/ /electron.lbl.gov/ marchesini/dph)





Spin-polarized photoelectron holography: Transforming spin-sensitive instead of : should permit imaging short-range magnetic order (Kaduwela et al. PRB 50, 9656 (1994))

Spin-polarizedphotoelectron holography:direct imaging of magneticmoments in 3D:

Normal image-

Spin-selective images-

Δ r U r U r

k

3

k̂

exp ik r

Δ' rexp ikr χ k χ k d k

23U r χ k exp ik r ikr d k

Simulation: MnO-AF cluster

Kaduwela et al. , Phys. Rev. B 50, 9656 (1994); Fadley et al., J. Phys. B

Cond. Matt. 13, 10517 (2001)

Photoelectron holography-Advantages:Element-, chemical state-, and spin- specific local structureLong-range order not requiredLarge % effects, easy to measureSurface sensitive, if that’s what you wantAvoids 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 and instrumentation issues:

--Present statusDetectors not fast enough/linear enough to handle “snapshot”

spectra (cf. ALS project)

Protective shell

Microchannel plates

768 collector stripsAmpl./Discr.(CAFE-M)

Counter/digital readout (BMC)Ceramicsubstrate

Spring clamps for circuit board and MCP cover

ALS GHz-RATE 1D DETECTOR768 channels, 48 spacing, >2 GHz overall

Energy

direct

ion

Photoelectron holography-Advantages:Element-, chemical state-, and spin- specific local structureLong-range order not requiredLarge % effects, easy to measureSurface sensitive, if that’s what you wantAvoids false minima in structure optimizationDisadvantages:Strong scattering leads to multiple scattering (but can be suppressed by multi-energy datasets)Not bulk sensitive, if that’s what you wantRequires at least short-range repeated order

Future prospects and instrumentation issues: --Present statusDetectors not fast enough/linear enough to handle “snapshot”

spectra (cf. ALS project)Scanning of sample angles not fast enough

--Future possibilitiesMuch faster multichannel detectors up to GHz rangeFaster scanning of angles via snapshot mode“Tiling” of hemisphere with analyzers to reduce angle scanning

SRBeam

Detector

Graphite analyser

2f

Sample

Focal spot

K

K

Graphite analyser

Marchesini, Tegze, Faigel et al.,Nucl. Inst. & Meth. 457, 601 (2001)

XFH at ESRF:

Graphite analyzer

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 distributionNi K Hologram

Mn K Hologram

Image

Image

ESRF--S. Marchesini et al. Phys. Rev. Lett. 85, 4723 (2000)

Al.704 Pd.210Mn.086 Quasicrystal First ALS Holograms

First application of hard x-ray holography to complex system Structural information in direct space without any assumed model

Future dataEnvironments around both Mn and Pd imagedData at many energiesextended range of imagingMore precise atomic environments in the first 5–6 coordination shells, evidence for inflationRigorous test of theoretical models

Pd L

Mn K

Bragg spots

Sample edgeReconstruction

Samples: P. Thiel P. Canfield

Mn K Hologram

0

6

-6

6 Å-6 Å

1 (a.u.)

MnO (100)(b) Expt. (c) Calc.

(d) Mn-atom image (scales in Å)

(a) Experimental setup: (Marchesini et al.)

Det

PC

Motion

Acquisition

Drivers

Acquisition

Motion

Clock

ALSMonochromaticx-rays

High speed motion-acquisition-d/dt = 3600o/sec

d/dt =

2o/sec

Ge solid state det.-- up to 4MHz

(La, Sr) Mn O

X-RAY FLUORESCENCE HOLOGRAPHY AT THE ALS

(b-e) First data

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

(e) Expt.

CMR: (La,Sr)3Mn2O7

F.T.

La1-xAxMnO3 , A = Ca, Sr

, Ca

LaMnO3 shows long range Jahn-Teller distortions (JT)

When x > 0, one theory predicts the coupling of the itinerant

electrons with local, short-range JT dist.

in the T > Tc insulating phase

Cubic Orthorhombic

Schematic view of the tetragonal Jahn-Teller distortions in the ab plane

Key to CMR effect?

Jahn-Teller distortions probed with x-ray fluorescence holography: new insights on the CMR effect?

2.151.92





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.

Optical constants for Fe and Ni through the Ni K(1s) edge

RESONANTX-RAY FLUORESCENCE HOLOGRAPHY:A theoreticalstudy(cf. Van Hove talk)

2kkk

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

..]exp[ cciikrFj

jjj rkk

..expeff ccriikrF

jjjj

kk

kkk

jjjjjjj ir

kiFir

kiFF rkkrkk ˆ

2sin2ˆ

2expeff

Normal hologram

Differential hologram

(a) (c) RXFH--Fe suppressed(b) MEXH--Fe & Ni

3.55×2 Å

Fe2

Fe1Ni1

(d) MEXH--Fe & Ni (e) RXFH--Fe suppressed

FeNi3: Structure and simulated holographic images in normal inverse (MEXH) and resonant (RXFH) modes

Fe2

Ni1

Fe1

Omori et al., PRB 65, 014106 (2002)

Ni1

Fe1

Fe2

Ni1

Ni1

Resonant x-ray fluorescence holography

4.0 4.2 4.4 4.6 4.82

4

6

8

10

12

14

Resonant X-Ray Fluorescence Holography

Te L3 Absorption Coefficient (in e-)

Photon energy (keV)

CdTe structure

Measuring Cd x-ray holograms above and below the Te L3 edge from CdTe

Identification of near-neighbour scatterers, ‘true color’ holography.

1-2=a

1 2

3 4

4-2=b

1

2 3

4

a b

averagesource/

detector site

Identify viaresonant

XFH?Identify viaresonant

XFH?

Some potential applications of x-ray holography:

source or detector site




averagesource/

detector site

averagesource/

detector site

averagesource/

detector site

Active sites in biorelevant molecules




averagesource/

detector site

averagesource/

detector site

averagesource/

detector site

…and ultimately more dilute species:

X-ray fluorescence holography-Advantages:Element-specific local structure

Weak scattering, better holographic imagingLong-range order not requiredMosaicity up to few degrees OKAvoids false minima in structure optimizationWith resonance, near-neighbor identification?With CP radiation, short-range magnetic order imaging?

Disadvantages:Small % effects, need approx. 109-1010 counts in hologramRequires at least short-range repeated order

Future prospects and instrumentation 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 overallhologram in 0.1-10 sec, or in one LCLS pulse

X-ray fluorescence holography-

E.g., the LBNL Gammasphere:

110 large volume, high-purity germanium detectors

Why not!

The End

holographic imaging of atomic structure: where is it and where can it go? c.s. fadley

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