Materials Characterization

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Materials Characterization

• ITG Forum
• October 1, 1998
• Martin U. Pralle
• Dept. of Materials Science and Eng.

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Transmission Electron Microscopy
Electron Gun

• Operates exactly like a Light Microscope except
  with electrons
• Electrons are focused by electromagnetic lenses
• Samples must be very thin to pass electrons
  through (lt1000 Å)
• Samples diffract electrons and then are
  recombined in the image

Condenser lens
Objective lens
Sample
Diffraction lens
Screen
Camera
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Supramolecular Objects
triblock rodcoil molecule
diblock coil
Self- Organization
rigid aromatic rod
mushroom shaped nanostructure
Stupp, S. I. LeBonheur, V. Walker, K. Li, L.
S. Huggins, K. Keser, M. Amstutz, A. Science
1997, 276, 384-389.
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TEM Sample Preparation
sample
Embed in epoxy Cut with a diamond knife
Utramicrotomy
Thin sliver
Solution cast/crystallized
Diamond knife
Dry from solution on a water surface or direct to
a TEM grid
Grind to thin disc and then bombard with ions
until it thins down and a hole forms
Ion milling (not available in ITG)
Freeze fracture Cryo
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Order in Self Organized Material
solution cast film
FFT
9.2 nm

• 120 Å nanostructures
• nanostructures exhibit positional order on an
  oblique superlattice
• layered material

Intensity (au)
SAXS pattern shows molecular layer
spacing Extended length 110 Å
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2
3
2? (deg)
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Interference or High resolution
Contrast
Scattering or Diffraction
Diffracted only
Scattered or Diffracted
Phase
q
Results from defocusing the TEM
Aperature
6.3 nm
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Osmium Tetraoxide, OsO4 RuO4 Uranyl
Acetate Phosphotungstic Acid
Double bonds Double bonds and phenyl
rings Esters, amines, ethers Ethers
Staining
unstained
stained
crystalline
stained
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Electron Diffraction
e- beam
Bragg Law
q
2dsinqnl
Atomic Planes
dspacing
sinq a rring
Calibrate using gold standard
dspacingrringconstant
constant/runknown dspacing(of unknown)
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Structure Determination
7.95 Å
(110)
5.15 Å
(210)
(200)

• a - b plane reveals a rectangular unit cell
  projection
• The unit cell dimensions a 7.95 Å and b 5.15 Å
  match those observed for polymer PPV

hydrogen in blue carbon in white oxygen in red
Molecules are perpendicular to the film
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