Zone Plate Scanning Microscopes and Applications at the APS

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Soft X-ray Microscopy at the APS
Ian McNulty
Argonne National Laboratory
Wednesday, 9 October 2002
Many thanks to ...
Joe Arko Advanced Photon Source Ralu
Divan Kurt Goetze Tim Mooney David
Paterson Stefan Vogt Petr Ilinski Shenglan
Xu Sean Frigo Northern Arizona
University Cornelia Retsch Saint-Gobain Sekurit
Deutschland Nathan Krapf University of
Chicago Steve Wang Xradia Corporation Wenbing
Yun Xradia Corporation Erik Anderson CXRO,
Lawrence Berkeley National Laboratory Franco
Cerrina CXRL, University of Wisconsin at Madison
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Summary

• Motivation
• APS efforts
• Scanning microscopy
• Flash methods
• Future

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1-4 keV access most of periodic table
K
L
M
M
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1-4 keV x-rays applications

• Materials science
• Nondestructive in situ imaging of buried
  structures
• Visible/electron-opaque samples, less charging
  than with electrons
• Contrast at K,L,M-edges in industrially
  important materials (AI, Si, Ti, Cu, Ga, Ge, As,
  Sm, Eu, Gd, W, Au, . . .)
• Study electromigration and fabrication defects
  in chip interconnects

• Biology
• Better resolution than optical, less damage
  than electron microscopy
• Specimens can be initially living, wet,
  unstained, and in air
• Natural Na, Mg, P, S, Ca contrast in this
  energy range

• Environmental science
• Study S in soils, fossil fuels, catalyst
  sulfidation, lubricants
• Chemical as well as elemental contrast

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Soft x-ray microscopy at APS

• Magnetic materials 4-ID-C (J. Freeland)
• XANES PEEM
• MCD, MLD PEEM, scanning (future)
• Materials, biology 2-ID-B (D. Paterson)
• Transmission scanning, holography, full-field
• Fluorescence scanning
• Tomography scanning
• Microdiffraction scanning

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Chemical and magnetic microscopy at 4-ID-C
PEEM images provide direct map of chemical and
magnetic structure
Chemical map (Co bright)
Magnetic map (M? bright)
Beam direction
1 mm x 1 mm x 15 nm Co nanodots on Al
substrate (as dep., no field history)
J. Freeland, D. Keavney, R. Winarski (APS) J.
Shi, W.C. Uhlig (Univ. Utah)
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2-ID-B intermediate-energy beamline
Monochromaticity 500 typ., gt 3000 peak Coherent
area 50 ?m ? 50 ?m Coherent flux 2 ? 105 ph/?m2
/s/0.1 BW Focused flux 4 ? 107 ph/s/0.1 BW
50 nm spot 2 ? 108 ph/s/0.1 BW 150 nm spot
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Scanning x-ray microscope
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2-ID-B SXM specifications
Zone Plates
Material Radius Central stop radius Zone
thickness Finest zone width Transverse
resolution Focal length (1.83 keV) Depth of
field ( " " ) Meas. Efficiency ( "
" )
Au Au Ni Ni 38.5 40 45 49 - -
- 20 420 650 110 130 100 50 45 40 122 61 55 49 11.
4 5.9 6.0 5.8 72 18 15 12 20 12 2.5 3.0
?m µm nm nm nm mm ?m
Sample Stage (XYZ?)
Coarse
Fine
Linear range Linear resolution Linear
velocity Angular range Angular resolution Max
scan speed
?25 500 2 360 0.001 0.1
?0.1 0.8 20 360 0.14 0.1
mm nm mm/s degrees degrees ms/pixel
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Contrast of a 100-nm Al wire on 1 µm of Si
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Elemental contrast in Al/W/Si chips
STXM image at 1553 eV. Al interconnects
become transparent below Al 1s edge (1559 eV),
whereas W vias joining interconnects still appear
dense.
STXM images of two-level Al/W/Si test
structure at 1563 eV. SiO2 substrate was thinned
to 5 µm. Sample courtesy of DEC.
Steve Grantham Nat'l Inst. of Standards and
Technology Zachary Levine Andy Kalukin SAIC Marku
s Kuhn Intel Corporation
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Scanning nanotomography of AI/W/Si chips
5 µm
1 µm
500 nm
3D Bayesian reconstruction of two-level structure
at 1750 eV
Normal-incidence scan of electromigration void
3D reconstruction of ragged end of void
Z. Levine, et al., Appl. Phys. Lett. 74, 150
(1999) Z. Levine, et al., J. Appl. Phys. 87, 4483
(2000)
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Nanoscale metrology in Cu/W/polyimide chips
(a) Schematic side view of a two-level Cu/W test
structure. (b) STXM image at normal incidence.
(c) Elevated surface plot. Sample courtesy of IBM.
Comparison of various line scans through structure
X. Su, et al., Appl. Phys. Lett. 77, 3465 (2000)
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1-4 keV x-rays biological applications

• Natural contrast for nuclear and mitochondrial
  DNA at K-edge of P (2149 eV)
• Probe cell ion transport and membrane
  permeability at K-edges of Na (1.09), Mg (1.28),
  K(3.82), Ca (4.04 keV)
• Co-locate lighter elements with trace metals
  mapped by hard x-ray microscopy, at higher
  resolution
• Study chemical speciation of important inorganic
  elements (Mg, Al, Si, Ca), e.g. in marine
  organisms

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Phosphorus XANES
P Ka fluorescence from NaPO4
P 1s absorption spectra
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Simultaneous transmission, fluorescence detection
Gd 3d5/2, 3d3/2
Si 1s
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TiO2-DNA nanocomposites in mammalian cells

• Cell is transfected with TiO2-DNA
  nanocomposites
• DNA targets specific chromosomal region
• TiO2 photocleaves DNA strands upon illumination
• Potential use in gene therapy

Map Ti distribution using x-ray induced
K? fluorescence, to quantify success rate
of TiO2-DNA transfection and visualize
target Affinity of transfected DNA to
ribosomal DNA causes nanocomposites to
localize to the nucleolus
?g/cm2
?g/cm2
2.2
5.8
Zn
Ti
5 ?m
0.0
0.0
G. Woloschak, I. Moric, T. Paunesku, N.
Stojicevic (Radiation Biology Dept., Northwestern
Univ.)
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Phosphorous absorption imaging
Mouse PC-12 cell (fixed, dried)
Cell nuclei, separated by centrifugation (fixed,
dried)
10 µm
5 µm
5 µm
Energy 2170 eV Step size 50 nm Dwell 10
ms Scan time 20 min
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Energy-resolved fluorescence mapping
Whole mouse PC-12 cell (fixed, dried) Detergent
wash, ethidium bromide stain
5 µm
Transmitted
Na Ka
Br La
2 µm
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Nuclear contrast with P fluorescence
P Ka
Si Ka
5 µm
Energy 2200 eV Step size 150 nm Dwell 1
s/pixel Scan time 4 h
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What about radiation damage?
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Flash imaging methods

• Holography
• Use x-ray optics to form reference wave and
  object illumination
• Full-field imaging
• Use x-ray optics to magnify sample image
• Diffraction with phase retrieval
• X-ray optics useful but not required

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Quantitative phase contrast by holography
Hologram of 1 µm Al spheres on 100 nm formvar
membrane
Difference between two holograms at different foci
Reconstructed phase
B. Allman, A. Barty, P. McMahon, K. Nugent, D.
Paganin, J. Tiller (Dept. of Physics, Univ.
Melbourne)
B. Allman, et al., JOSA A17, 1732 (2000) J.
Tiller, Ph.D. Thesis, U. Melbourne (2001)
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Full-field phase imaging
Full-field image of 2 µm spider silk
Difference between in- focus, defocused images
Reconstructed phase
B. Allman, et al., JOSA A17, 1732 (2000)
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Phase imaging of optical fiber
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Phase nanotomography of Si AFM tip
3D reconstructions of real part of refractive
index of projections. (a, b) Horizontal slices
through tip. (c) Vertical slice. (d-f) Volume
renderings. Measured d 5.0 0.5 x 10-5 ,
calculated d 5.1 x 10-5.
P. McMahon, et al., Opt. Commun., in press
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Future developments

• Scanning microscope
• New ZP on order (50 nm outermost zone, 450 nm Au)
• Multiple SDDs to increase fluorescence acceptance
• 2K x 2K fly scans
• Extend quantitative phase imaging to 50 nm level
• Improve alignment for df/dz series
• Solve twin-image problem with TIE
• Determine limits on coherent flux required
• 2-ID-B beamline
• Multilayer gratings on order

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Conclusions

• 1-4 keV region highly attractive for x-ray
  microscopy
• 2-ID-B SXM is a workhorse instrument at APS
• 50 nm (2D), 150 nm (3D) resolution
• simultaneous transmission and fluorescence
• Goal reach photon limits near 10 µs/pixel
  (transmission) 0.1 s/pixel (fluorescence)
• Developing holography, coherent full-field
  imaging
• Obtain quantitative absolute phase
• Applicable to flash x-ray sources
• Beat radiation damage problem!

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