One Angstrom Imaging and Spectroscopy at SuperSTEM A synchrotron in a microscope

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One Angstrom Imaging and Spectroscopy at
SuperSTEMA synchrotron in a microscope?

• Andrew Bleloch and Mervyn Shannon
• on half-time secondment from Intertek MSG,
  funded by a Royal Society Industrial Fellowship

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Spherical aberration
Perfect lens
focus plane
corrector effectively introduces -Cs before
objective lens to cancel Cs
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Transmission Electron Microscopes

• TEM

• STEM

IHAADF a nZ2
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Electron Energy-Loss Spectroscopy (EELS)
Quantitative porphyrin
Bonding/electronic state
http//eels.kuicr.kyoto-u.ac.jp/eels.en.html
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What do we have?

• 3rd order corrected VG501 AC-STEM
• 5th order corrected Nion UltraSTEM
• imaging
• HAADF (Z-contrast), BF
• resolution sub Angstrom . just
• EELS pico-analysis
• spatial discrimination - single atom column, c.
  1Å
• spectral resolution - 0.35eV . cold FEG
• elemental, chemical, electronic state
• approaching single atom sensitivity

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The new microscope!

• Second Nion UltraSTEM column
• 5th order corrector
• Modular design
• 100kV VG gun
• 3 condenser lenses
• Change settings
• x,y,z stage
• Move sample to crossover
• Keep electron trajectory unchanged
• 2 degrees of tilt
• 30º both directions
• Magazine for 5 sample cartridges
• 15 minute sample change

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Samples

• Nanoparticles
• disperse powder
• extraction replica
• Thin sections lt100nm
• cut, polish, ion mill
• FIB
• microtomy

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Detecting and identifying single atoms
0-D
La in CaTiO3
Varela, Findlay, Lupini, Christen, Borisevich,
Delby, Krivanek, Nellist, Oxley, Allen and
Pennycook 2004 Phys. Rev. Lett. 92, 095502
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1-D
EELS from Partial Dislocations in GaN
Arslan, I., Bleloch, A et al Phys. Rev. Lett.
(2005), 94 025504
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Defects at the CoSi2/Si(001) interface
2-D
Si
Falke, M. et al., Appl. Phys. Lett. (2005), 64
20310
CoSi2
Si
001
CoSi2
-110
2-D/1-D
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3-D
NiSi2 precipitate in Si Interfaces are on
(111) planes
shape
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HAADF Images
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3D Model of QDs
5nm
3D model

• L Lateral length of dot
• H Height of dot
• Wt Width of the top of dot
• D Depth of diffused In under dot
• We Width of the end of diffused In

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Elemental Analysis By EELS
In content x of Dot and WL
PS Since the size(30nm) of dot is is 1/3 of
whole thickness (90nm), the signal (purple) from
wetting layer above and below dot along
z-direction is weighted as 2/3 of whole WL(red).
In content x is the quotient of num. of In and
that of As.
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Ferritin in diseased human liver
Y. Pan U. Leeds
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Single particle analysis of ferritin cores
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EELS studies of Fe oxidation state

• beam damage considerations
• extrapolation to t0
• mainly octahedral Fe 3, 6LFh like
• interface - smart acquisition methods

Maghemite standard spectra
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SuperSTEM for nanotoxicology
Work carried out with Alex Porter, the University
of Cambridge.
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SuperSTEM for nanotoxicology (3)
Fe M2,3
?Ep
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Atomic resolution EELS mapping Bi0.5Sr0.5MnO3

• HAADF image of the analyzed area. 30-35 nm thick
  Bi0.5Sr0.5MnO3 along the lt001gt zone axis.
• Oxygen EELS map. after accurate background
  subtraction (using principal component analysis),
  a 30 eV window was used to obtain this image.
  Next to the EELS maps, a summation of all the
  spectra is shown. The grey energy window
  indicates the used energy window.
• Manganese EELS map.

Bosman et al, PRL, 086102 (2007)
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Bi0.5Sr0.5MnO3

• 12 nm thick and imaged along the lt110gt zone axis.
• Oxygen map (b) is non-intuitive. Along this
  crystal direction, a tilt in the MnO6 octahedra
  is expected (from earlier neutron and X-ray
  scattering on this material). This small atomic
  displacement is indicated by the zig-zag pattern
  of the oxygen circles. Amazingly, a hint of it is
  visible in both the simulation and the
  experimental Oxygen map.
• The Oxygen signal on the columns that the Oxygen
  shares with the Bismuth and Strontium is
  particularly low, indicating dechanneling effects
  even for this thin specimen.

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Access

• SuperSTEM is used when other microscopes cannot
  answer the question posed
• EPSRC funded 10 year project (2001-2011)
• Now Core grant 7030
• resource for (UK) academia through peer review
• Small grants (up to 20 user-days)
• Large grants
• quick response mode
• direct access for industry on commercial basis -
  MDS
• gt 75 different user groups to date, gt200
  different samples
• Remote access
• interact with skilled operator
• Net Meeting, VNC Client