Soft and Hard X-ray Microscopy

Ian McNulty
Advanced Photon Source,
Argonne National Laboratory

Cheiron School 2008
SPring-8

Outline
1. Fundamentals
resolution
contrast
sources
optics

2. Direct methods
projection imaging
full-field imaging
scanning

3. Indirect methods
microdiffraction
coherent diffraction
holography
References:
1. M. Howells, "Soft-x-ray microscopes," Physics Today 38, 22 (Aug. 1985).
2. J. Kirz, "Soft X-ray microscopes and their biological applications," Q. Rev. Biophys. 28, 1 (1995).
3. J. Als-Nielsen and D. McMorrow, Elements of Modern X-ray Physics (Wiley, New York, 2000).
4. D. Attwood, Soft X-Rays and Extreme Ultraviolet Radiation: Principles and Applications (Cambridge, 2007).
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Image formation as a scattering process

k scatt"

Incident waves with initialmomentum kinc are elasticallyscattered into new direction kscattwith momentum transfer !k.

!k

k inc
ky

kx

k

k scatt

k scatt
k inc

!

kz

k inc

kz

Ewald
circleobject spatial
frequency limit

Ewald sphere is defined by conservation of momentum. Only spatial frequencies on
the Ewald sphere are accessible to the imaging process, limiting attainable resolution.
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Diffraction limits to resolutiony

Point-spread functionx

P(x,y) =with

sin x sin y
x
y

x=

kax
z

a
z

y=

,

kay
z

!
Transverse!

R = 0.5

!

"
NA

where

!

a
z
2"
k=
#

NA ~

P(x)

R

"

1.0

kax/z

!

Bragg's law"k = k inc # k scattk 2x + k 2y + (k z + k inc )2 = k 2inc(0 " #k " 2k inc!)

For extreme-angle ray (xz plane, k y = 0) with!

!
Longitudinal

DOF =I. McNulty!

P(x,y)

!
"
(NA)

2

and

!

kx =

2" 2"
=
NA
2R
#

k 2x
kz =
2k incCheiron School 2008 / SPring-8!

(k z << k inc )3 October 2008!

What do we mean by "resolution"?

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Coherence
longitudinal coherence
#

!#

lc

"2
~
#"

"c

#2
~
c$#

!

wc

"z
~
d

wc

d " # = $ /2%!

"x "p # h /2!

transverse coherenced2$!
I. McNulty!

Cheiron School 2008 / SPring-8

3 October 2008!

Coherent vs. incoherent

Scanning and full-field microscopy are incoherent methods• Transfer function is linear in the field intensities• Characterized by sloping function down to 2NA
Diffraction and holographic microscopy are coherent methods• Transfer function is linear in the field amplitudes• Characterized by flat top, sharp cutoff at limiting NA
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Why use x-rays?
! Penetration through whole cells and thick materials withminimal multiple scattering: “clean” images and spectra! Short wavelengths, so high spatial resolution is possible! Short pulses, so high time resolution is possible! Coupling to core-level electrons: element detection, “clean”
measurement of electronic and chemical states! Coupling to electronic spin via polarization: probe magnetic
states and ordering
But: ionizing radiation, so repeated high-resolution imaging
of radiation-sensitive samples (e.g. live cells) is not possible.

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Contrast mechanisms in x-ray microscopy• Access a wealth of information" Absorption

measure electron density" Phasemeasure real part of refractive index" Fluorescencemeasure elemental distribution" Spectroscopy

extract chemical state, spin state" Diffraction

reveal structure, strain, mag. charge• Natural sample contrast is possible; staining not required• Image structure of thick samples, sectioning not required• More penetrating, less damage, less charging than with electrons

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Refractive index and contrast

re 2
n = 1" # " i$ = 1"&
2%

• Absorption contrast:!

' ni fi (0)i

A = A0 exp("inkt)k = 2# / $!

sensitive to Im(n)~ 2"# (x, y)t / $!

• Phase contrast:
sensitive to Re(n)~ 4 "# (x, y)t / $!
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Elemental sensitivity at absorption edges

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

The "water window"

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Fluorescence spectroscopy

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Why use synchrotrons?

Synchrotron sources offer••••

Brilliance (small source, collimated)
Tunability (IR to hard x-rays)
Polarization (linear, circular)Time structure (short pulses)! Undulators produce the mostbrilliant x-ray beams available
B = photons/source area, divergence, bandwidth

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Undulator radiation! SR sources (except FEL) are incoherent, but highly forward directed
due to relativistic effects$ ~ 1/%! Spatial and temporal filtering (pinholes, monochromators) isneeded to select the coherent flux
Fc ~ # 2 B! Only the coherent flux can be focused into a diffraction-limited spotor be used to form interference fringes

p

p

x

x
Ac

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Focusing optics for x-rays
Achieving high NA is challenging because x-rays interact weaklyn = 1 - & - i'&,' ~ 10-3 to 10-6

Refractive (compound refractive lenses)(|n| ! 1

~ 50 nmLow efficiency, highly chromatic, aberrations

Reflective (Kirkpatrick-Baez mirrors)~ 40 nmHigh efficiency, achromatic, limited to ~10 nm

Diffractive (Fresnel zone plates, MLLs)~ 20 nmModerate efficiency, limited to ~10 nm except MLL

Waveguides~ 20 nmLow efficiency, 2D is challenging
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

useful complement to

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

2. Direct methods

Projection

Imaging

Scanning

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Different regimes of x-ray imaging

2afar-field
Fraunhofer

near-field
Fresnel

X-ray beamz ~ a2 / !

absorption
radiographphase
contrast

Kagoshim a (1999)

I. McNultyz >> a2/!

in-lineholography

Jacobsen (1990)

Cheiron School 2008 / SPring-8

coherent
diffraction

Miao (1999)

3 October 2008

Phase contrast: tool of choice for low-absorption samples
b

a

a

b

(a)Dust mite and (b) tomographically reconstructed fly leg joint,recorded with ~8 keV x-rays and propagation phase contrast.
S. Mayo, Opt. Express 11, 2289 (2003)
Small fish, recorded with three-grating method
and a standard x-ray tube (40 kV/25 mA). (a)Transmission. (b) Differential phase contrast.
F. Pfeiffer, Nature Phys. 2, 258 (2006)

Moth wing, recorded with 4 keV x-rays.
(a) Bright-field. (b) Differential interference contrast.
B. Kaulich, T. Wilhein, J. Opt. Soc. Am. A19, 797 (2002)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Full-field and scanning x-ray microscopes

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

XM-1 microscope at the ALS

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Wet specimens can be studied by x-ray microscopy

Whole, hydrated mouse epithelial cell
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Cryo-preparation of sample mitigates radiation damage

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Interconnects in chips are more "hardy"

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Circular dichroism contrast using polarized x-rays

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Magnetic x-ray microscopy

Magnetic recording materials:
FeTbCo multilayer with Al cap layer
P. Fischer (MPI), G. Denbeaux (CXRO)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

3D imaging

R ! 0.61 # / NA|n| ! 1(

DOF ! 1.22 # / (NA)2 = 2 R2 / (0.61#)
NA << 1(

DOF << R

Synthesize larger NA with multiple views

!t
R

DOF
!
l

Cannot improve R, only DOF by tomography

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Computed tomography

1 Record many projections through sample over wide angular range.
Projections at angles q contain:

I(x, y, ! ) = I0 e " $ µ! ( x # ,y #, z# )dz#

2 Reconstruct 3D sample density from suite S of projections

Invert S {I(x, y, ! )} " µ (x, y, z)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Soft x-ray nanotomography

Frozen hydrated yeast Saccharomyces cerevisiae C.
Larabell, M. Le Gros, Mol. Biol. Cell 15, 957 (2004)

Frozen hydrated alga Chlamydomonas
reinhardtii: D. Weiß, G. Schneider, et al.,Ultramicroscopy 84, 185 (2000)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Quantitative phase tomography! Defocus series (a, b, c) and phase (d)of a silicon AFM tip! Quantitative 3D reconstructions ofreal part of refractive index from ±70°
tomographic projections through tip! Calculated & = 5.1 x 10-5
Measured & = 5.0 ± 0.5 x 10-5

P. McMahon et al., Opt. Commun. 217, 53 (2003)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Full-field microscopy with hard x-rays

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Beamline for scanning microscopy (soft x-ray)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

1-4 keV scanning x-ray microscope at APS 2-ID-B

OSA

sampleAPD orsegmented
detector

X-ray probe• Fresnel ZP• 60 nm spot
• 108-109 ph/szone plate

Contrast modes• Transmission• Fluorescence• Micro-XANES

fluorescence
detectorscan/rotation
stage

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Defects in buried interconnects
Example: Ta-lined Cu interconnect, W vias

0º
10 µm

30º

Z. Levine et al., J. Appl. Phys. 95, 405 (2004)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

X-ray spectromicroscopy is valuable to study P speciation
Marine sediments contain complex, heterogeneous P chemistry.
P typically shows little covariance with most other elements.

Al

P

Si

sum

2 !m

! Occasionally find odd P-containing minerals with distinctive P-XANES that
do not match closely with any known Al-phosphate mineral! Previously unknown in marine samples - Riverine or Aeolian source?
J. Brandes et al., Marine Chem. 103, 250 (2007)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Use phase contrast for biological specimens

Complex transmission function: exp(i & kt) exp(- ' kt)phase shift

absorption

X-ray DPC

X-ray abs.

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

STXM: differential phase contrast
Configured
detector

Central
stop

Zone
plate

Specimen
OSA

5 µm latex spheres, E = 2.5 keV

T–B
T+B

DPCV
=
signalM. de Jonge et al., PRL 163902, (2008)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Pennate diatoms

radians!m

Phase
Thickness

2535 eV, 30 nm steps,
5 ms dwell (3 h scan)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Hard x-ray scanning flourescence microscope

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Copper is an essential trace element for all life forms• Catalyzes production of highly reactive oxygen species( oxidative damage to lipids, proteins, DNA, etc• Defects in regulatory processes may led to:

CTAP-1 visible
fluorescence

Cu XRF map# Menkes syndrome# Wilson’s disease# Amyotropic lateral sclerosis (ALS)# Alzheimer’s disease
Mouse fibroblast cell + 150 "M CuCl2• Need to be understand cellular uptake, trafficking, storage of Cu• Novel Cu(I) fluorescent sensor (CTAP-1) was recently developed( Does it reflect the true cellular distribution?
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

!-XANES indicates Cu(I) is present (reducing environment)

absorbance2.0

cytoplasm

1.5
1.0
0.5
0.0
8.96

8.97
8.98
8.99
energy [keV]

9.00

9.01

0.8

rel. absorbancenucleus

0.6Standards
Cu(I)

0.4

Cu(II)

0.2

0.0
8.97

8.98

8.99

9.00

9.01

9.02

energy [keV]

L. Yang et al., Proc. Natl. Acad. Sci. 102, 11179 (2005)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Arsenic distribution and speciation in rice grains• There is worldwide concern over elevatedarsenic concentrations in regions where
rice paddy fields are irrigated with As
contaminated groundwater.
• Rice production increasingly occurs in As
and metal contaminated soils in Asia
• S-XRF was utilized to locate As in polished(white) and unpolished (brown) rice grainsfrom the United States, China, andBangladesh

US White Rice
Bangladesh Brown RiceA. Meharg, E. Lombi, P. Williams, K. Scheckel, J. Feldmann,
A. Raab, Y. Zhu, and R. Islam, Environ. Sci. Technol. 42, 1051 (2008)• As dispersed in white rice but localized in
the pericarp and aleurone layer of brownrice - Cu, Fe, Mn, and Zn localization
followed that of As in brown rice
• µ-XANES and bulk extraction revealed thepresence of mainly inorganic As anddimethylarsinic acid (DMA)• Percentage of DMA present in the grainincreased along with total As.
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

3. Indirect methods! Microdiffraction– Scanning (monochromatic/Bragg)– 3D differential-aperture x-ray microscopy(white/Laue)! Coherent diffraction imaging! Holography

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Is there lattice strain in zinc oxide nano-rings?
Termination at Zn (+) and O (-) results inspontaneous polarization along the c-axis
resulting in formation of nano-rings
Internal lattice strain and distribution needed to
study balance between mechanical andelectronic configurations for nano-sensor
applications.

X-ray
beam

(110)
(100)

X-ray fluorescence (Zn K)) map

t = ~20 nm

D=2.6 µm

Diffraction of Zn (110) from a section of the ring. Patterns were taken atangles $ across the rocking curve width
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

X-ray nanodiffraction explains strains
Image (220) reflections from ZnO nanoring with CCD using 10 keV x-rays!* = 27.5 o! Might expect that coiling stresswould cause a continuous strain
distribution from compressive totensile across the ring width.
!* = 27.5o

Patterns cover a $ angular range of 0.6o

! The two branches of the diffracted
intensity indicate existence of two
strain domains, with as much as 1.8%
difference in the (220) plane spacing.
! Data show the structure either
collapses into distinct domains
across the ring width, or exhibits
strain that varies little in width but(220)
reflection withup
incident$ = 49.4-49.7°(left tocontinuously
to 2.4%along theright, top to bottom). Vertical axis represents *ring arc.
direction (27.5°) and horizontal axis represents 2$

D=2.6 µm

Y. Xiao et al., JSR 12, 124 (2005)
I. McNulty

direction (6.6°) in each image.

Cheiron School 2008 / SPring-8

3 October 2008

Differential-aperture x-ray microscopy
3D depth-resolved, white-beam Laue diffraction techniquepolychromatic
undulator beamdiffracted-beamprofiler

CCD

K-B
mirrors
bulk sample

monochromator(removable)

B. Larson et al., Nature 415, 887 (2002)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

3D diffraction microscope at APS beamline 34-ID-E

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

DAXM illuminates the 3D structure of aluminum
4

5+6 +31 µm3 volume in Al polycrystal

2

100
6
4
2

10
6
4
2

1

20

30

40
Rotation angle(°)
Relative
Orientation
(o)

50

60

CCD
diffracted
beam profiler
microbeam• Intra- and inter-granular information• Grain boundary morphology and type
• Misorientation axis/angle between grains• 3D microtexture• Grain size-distribution

5 µm
TEM - Polycrystal Al
I. McNulty

W. Yang, et al., Micron 35, 431 (2004)
Cheiron School 2008 / SPring-8

3 October 2008

Coherent diffraction and holography: "lensless" imaging

Coherent Diffraction

Holography! Object wave (diffraction) is
detected directly! Diffraction intensity corresponds
to autocorrelation of object

Resolution:! Coherent reference wave interfereswith object wave to form hologram! Hologram intensity corresponds toconvolution of object and referencetransverse
longitudinalContrast:
I. McNulty

Cheiron School 2008 / SPring-8~ #/NA~ #/(NA)2, |f12 + f22|
3 October 2008

Coherent diffraction x-ray imaging
Lensless method - resolution limited only by wavelength, signal! Two-step process: record coherent diffraction pattern,recover object structure numerically (iterative phase retrieval)! Sensitive to phase as well as absorption of the specimen! Get 3D by tomographic methods; no depth of field limit! But: must assume some a priori information to recover phase,e.g. known object extent or illumination profile

resolution ~ # / angular size

J. Miao, et al., Nature 400, 342 (1999)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Iterative phase retrieval
Real Space

k-Space

NxN
Object in
2N x 2N
MatrixFFT

Force Intensity
Outside Of Object
to Known Value

Set Magnitude
to Speckle Image

FFT

-1

2N x 2N
Detector
Pixel
RandomStart Phase

R. Gerchberg and W. Saxton, Optik 35, 237 (1972);
I. McNulty

J.R. Fienup, Appl. Opt. 21, 2758 (1982)

Cheiron School 2008 / SPring-8

3 October 2008

Freeze dried yeast cell imaged by coherent x-ray
diffraction

D. Shapiro et al., PNAS 102, 15343 (2005)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Diffraction microscopy in 3D

Bragg gratings that diffract to acertain angle represent a specifictransverse and longitudinal
periodicity (Ewald sphere)

I. McNulty

Data
collection
Ewald
sphere over a series ofrotations about an axis fills in
3D Fourier space for phasing

Cheiron School 2008 / SPring-8

3 October 2008

3D coherent diffraction imaging

1 "m

1 "m

(a) SEM of pyramidal indentation in a 100-nm Si3N4 membrane lined with 50-nm Au spheres.
(b) 3D image reconstructed from 123 diffraction projections spanning -57° to +66°, using
reality and positivity constraints. (c) Large DOF projection. (d) Enlarged region of (c).

H. Chapman et al., JOSA A23, 1179 (2006)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Coherent x-ray diffraction can reveal strain in crystals! Double crystal monochromator
selects temporal coherence! Precision slits select spatiallycoherent fraction of hard x-ray beam
! Diffractometer is used to locate Bragg
peaks from an isolated nanocrystal! Rocking curves around Bragg peak
are recorded to obtain 3D data

Setup at APS 34-ID-C beamline

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Mapping crystal strain in 3D by CDI
0.5 "m Pb crystal grown on SiO2 substrate

Map series of diffraction patterns
about (111) Bragg peak

Diffraction data reconstructed by HIO

M. Pfeifer et al., Nature 442, 63 (2006)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

CDI setup at APS beamline 2-ID-B (1-4 keV)

Guard edges

4K x 4K
CCD

PinholeSampleX-raysI. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Buried structures can be probed with element specificity

In contrast to weak segregation theory, Bi is locally concentrated in Bi-doped Si crystals(a) Image below Bi M5 edge (2550 eV)(b) Image above the Bi M5 edge (2595 eV)(c) Difference(d) SEM image
C. Song et al., PRL 100, 025504 (2008)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Curved object illumination aids unique phase recovery
Aperture

Lens! Lens illuminates object with curved wavefront, defines field of view
! Object illumination is reconstructed by back-propagation, used toretrieve phase of object wave by iterative methods
K. Nugent et al., PRL 91, 203902 (2003)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

... and converges faster

Original

curved beam
illumination

I. McNulty

plane wave
illumination

Cheiron School 2008 / SPring-8

3 October 2008

FCDI setup
ZP

OSA

SampleCCD

X-raysScan Stage

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Fresnel coherent diffraction imaging of a gold test pattern

16 nm
50 nm

STXM image (1.8 keV)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Images reconstructed by FCDI

Phase

Magnitude withcolor-encoded phase

STXM image (1.8 keV)

G. Williams et al., PRL 97, 022506 (2006)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

"Keyhole" FCDI

Use reconstructed
illumination profile todetermine support inextended sample
H. Quiney,
Nature Physics 2, 101 (2006)

Ability to study extended
samples is essential formany real-world problems!
B. Abbey et al., Nature Physics 4, 394 (2008)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Recent results ("fuse bay" structure)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Alternative approach: ptychography
R. Hegerl et al., Phys. Chemie 74, 1148 (1970)
H. Faulkner and J. Rodenburg, PRL 93, 023903 (2004)
J. Rodenburg et al., Phys. Rev. Lett. 98, 034801 (2007)
P. Thibault et al., Science 321, 379 (2008)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Holography

Gabor

Fourier transform

Record hologram!

Reconstruct

I = a +b

2

2

2

2

= a + b +a*b+ab*2

bI = b a +b b +a*bb+abb*= aIb + b(Ia +Ib ) + background! Reference wave encodes
magnitude and phase of object wave!
! Reconstruct object wave by "re-illuminating" hologram withreference wave (or its C.C.)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Gabor holography

Reconstructed hologram (right) ofa NIL8 hamster neural fibroblastrecorded with 656 eV x-rays.
Estimated dose was 7.5 x105 Gy
S. Lindaas et al, J. Opt. Soc. A. 13, 1788 (1996)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Hard x-ray holotomography

Phase-sensitive image quantitative
phase map, and volume renditionof polystyrene foam (18 keV x-rays)

P. Cloetens et al., Appl. Phys. Lett. 75, 2912 (1999)

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

FT hologram formation
y
s

.

x

z

% 2ikz (( x%") 2 +( y%#) 2 )ikza(",#) =!

e&& a(x%s,y)ee
i$z

ik
ikz

dxdy

b(",#) =object wave!

I = a +b!
I. McNulty

2

2

e
b0 e
i$z

( " 2 + #2 )reference wave2

= a + b +a*b+ab*hologram intensity
Cheiron School 2008 / SPring-8

2z

3 October 2008

Reconstruction! Numerically take FT of hologram intensity to reconstruct! Spatially separated primary, conjugate object waves result! Weak curvature f(x,y) on object wave can be ignored
*

*

%

ik
(x"+ y#)z

a*b+ab* = "(s#)F(#,$) +"(s#) F(#,$)

Image terms:!

ikz
eF(",#) =f(",#) && a(x,y)f(x,y)e
i$z

where:!

"(s,#) = e

I. McNulty

!

ik
s#
z

ik

and

f(",#) = e2z,( " 2 + #2 )!

{a b + ab } = f (x " s,y) a(x " s,y) + f ("(x " s),"y)* a("(x " s),"y)*"1 ! *

FT

$

dxdy

*

Cheiron School 2008 / SPring-8

3 October 2008

CoPt magnetic labyrinth nanostructures
MFM, top viewside view

M
Co
Pt

M
5 µm x 5 µm

Sample: O. Hellwig (Hitachi)

continuous object
SiNx / Pt (24 nm) /[Co (1.2 nm) / Pt (0.7 nm)]50 /Pt (1.5 nm)

perpendicular anisotropy
I. McNulty/ magnetic storage media

Cheiron School 2008 / SPring-8

3 October 2008

UE56-SGM beamline and ALICE

samplebeam stop

CCD

coherent 778 eV beammagnetI. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Pinhole mask method
20 µm pinhole
UE56/1 SGM
beamline

worm domains
Co 2p3/2 XMCD:
778 eV
1.59 nmmask and sample

coherent illumination
Au mask
SiNx membrane
Magnetic film

SEM

2 µm

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

FTH

STXM

Reconstructed
resolution ~50 nm

W

Resolution~35 nm*S. Eisebitt, et al.,Nature 432, 885 (2004)

B

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Imaging resolution by x-ray holography

100

Resolution (µm)

1952

10

1972
1976
1974
1987

1986

1

1984

1988

0.1

1987
1988
1990
1992 2004

3rd Gen
SR's
APS

0.01
105

107

109

1011

1013

1015

1017

1019

1021

Source Brilliance (ph/s/mm2/mrad2/0.1% BW)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

What's in store for the future?
! Resolution of x-ray optics is improving steadily– 30 nm is routine– < 5 nm looks possible using MLLs

! Commercial x-ray microscopes are proliferating

7– Precision full-field and scanning instruments– Multiple contrast mechanisms available– Cryo-preparation will become standard (as for TEM)

8

– Bypass radiation damage with a single few-fs flash– Use pump-probe methods to study ultrafast dynamics– No lens to limit resolution or get between sample, detector
3 October 2008

5
2

6

! Diffraction and holographic methods are attractive for
x-ray lasers such as XFEL and LCLS !

Cheiron School 2008 / SPring-8

1

3! Hybrid scanning (ptychography) and single-view(keyhole) coherent diffraction methods broaden
range of applications

I. McNulty

49Ultrafast coherent diffraction with a free-electron laser

H. Chapman et al., Nature Physics 2, 839 (2006)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Now it can be done on a tabletop!

R. Sandberg et al., PRL 99, 098103 (2007)
J. Spence, Nature 449, 543 (2007)
R. Sandberg et al., PNAS 105, 24 (2008)
I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Summary! Resolution, contrast, sources, and optics for x-ray imaging! Direct methods: projection, full-field, and scanning! Indirect methods: microdiffraction, coherent diffraction, holography

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008

Many thanks to:David Attwood
Carolyn Larabell

LBNL/UCSF

Chris Jacobsen

Stony Brook University

Keith Nugent

Centre for Coherent X-ray Science

Stefan Eisebitt

BESSY

John Miao

UCLA

Qun Shen

NSLS-II

Karen Chen

Northwestern University

Jay Brandes

Skidaway Institute of Oceanography

Ellery Ingall

Georgia Institute of Technology

Ben Larson

Oak Ridge National Laboratory

Ross Harder
Barry Lai
Wenjun Liu
Xianghui Xiao

Advanced Photon Source

I. McNulty

Cheiron School 2008 / SPring-8

3 October 2008