TRANSMISSION ELECTRON
MICROSCOPY
Danqi Wang
Swagelok Center for Surface Analysis of Materials (SCSAM)
Case Western Reserve University
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OUTLINE
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SCSAM TEM Instrument
Introduction
Scanning TEM


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
Imaging
XEDS
EELS
TEM
Bright-field/Dark-field Imaging
 High-resolution Imaging
 Diffraction
 Energy-filtered TEM
Transmission Kikuchi Diffraction/ASTAR system
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
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Sample Preparation – Nanomill
SCSAM TEM Instruments
FEI Tecnai F30 (300 kV)
Zeiss Libra 200EF (200 kV)
TEM Sample Preparation
Focused Ion Beam
NanoMill Model 1040
Precision Ion Polishing System
Twin Jet Electropolishing System
FEI TECNAI F30
Operating at 300 kV
Resolution Limit ≈ 0.17 nm
High-resolution imaging
4
ZEISS LIBRA 200EF
Operating at 80, 120, and 200 kV
Energy Resolution < 0.5 eV
Analytical chemical analysis
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OUTLINE
 INTRODUCTION
Resolving Power of Microscopes
Transmission Electron Microscope
Useful Signals Generated from
Electron–Matter Interaction
Major Contrast
Mechanisms
for imaging
Mass thickness contrast,
Diffraction contrast,
Phase contrast (HRTEM).
It is essential that specimens for TEM be extremely thin, i.e, a few tens of nms
or less, so as for the energetic electron beam to penetrate and generate useful
signals.
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Modes of Imaging
Scanning Microscopy Full Frame Imaging
Scanning electron microscopy
Scanning transmission electron
microscopy
Focused Ion Beam
Source
↓
Object imaged
↓
Detector –
image pixel by pixel
Transmission electron microscopy
Regular light microscopy
X-ray imaging
Visible light photography
Source
↓
Object imaged
↓
Image forming lens
↓
Recording 2D media ––
CCD, negative
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What do can we learn?
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
 Structure Information
Elastic scattering
Morphology and microstructure.
Crystallographic structure
High Resolution
Transmission Electron Microscopy
Scheu et. al., Phil Mag A, 78(2) 1998, 439.



Composition
Inelastic scattering/XEDS
Elemental composition
Bonding state
Electron Energy Loss Spectroscopy (EELS)
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XEDS Elemental Mapping
Solid Oxide Fuel Cell
Purple –Zr; Yellow – LSM;
Green – Mn.
OUTLINE
 SCANNING
TRANSMISSION ELECTRON
MICROSCOPY (STEM)
Imaging
 EDS
 EELS

STEM
Gold on Carbon film
DF
BF
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Atomic Resolution
STEM
20 nm
Carburized Ferrite in 17-7 PH
Stainless Steel
1 nm
XEDS Elemental Mapping
Solid Oxide Fuel Cell
Purple –Zr; Yellow – LSM;
Green – Mn.
XEDS Line Scan in STEM
Cu-Al2O3 Composite
Si
Ca
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ELECTRON ENERGY-LOSS SPECTROSCOPY
EELS Analysis- Valence State
Grain-1
Grain-2
O-K edge results show the presence of precipitates in 2 valence states
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Electron Spectroscopy Imaging (ESI) Elemental Mapping
Ti – 452 eV
N – 398 eV
Oxygen map
Ti map
High Temperature MEMS Device
Color Mix: Red:Ti, Green:O
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Life Science Applications
Dark-field STEM Image of Fe Deposit in a
Erythroid Precursor Cell
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XEDS Spectrum of Fe Deposit
Grid
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EELS Spectrum of Fe in Different Oxidation States
Fe2+
FeCO3 (Siderite)
Fe2+ + Fe3+
Fe3O4 (Magnetite)
707 eV
OUTLINE
 TEM
Bright-field/Dark-field Imaging
 Diffraction
 High-resolution Imaging
 Energy-filtered TEM

Diffraction
Imaging
Full Frame Imaging
TEM imaging system can be
operated in two modes:
diffraction mode (left),
imaging mode (right).
Shown here are simplified ray
diagrams of both modes.
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Bright-field and Dark-field Imaging in TEM
BF
DF
DF
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Bright-field vs Dark-field Imaging
To identify grain size
and distribution in the
microstructure
Nanocrystalline Al. Scale markers are 500 nm.
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Bright-field vs Dark-field Imaging
To identify a second
phase in the
microstructure
Nitrided ferrite in
17-7 PH Stainless
Steel
High-resolution TEM (HRTEM)
A HRTEM image of an
interface between a Cu
particle and alumina
grain.
Grain
Boundary
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Electron Diffraction
Analyze the Lattice
Spacing and Orientation
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Convergentbeam electron
diffraction
(CBED)
3.620 Å
ZA [323]
HOLZ lines used for
lattice parameter 3.620 Å
determination
3.622 Å
ZA [221]
3.624 Å
Austenitic stainless
steel
ZA [111]
ZA [536]
MEASURED SAMPLE THICKNESS
FROM AUSTENITIC STAINLESS STEEL
Simulated
Simulated
Experimental
ENERGY-FILTERED TEM (EFTEM) IMAGING
Zero-loss EFTEM images:
Dislocations in 316 Stainless Steel after Low-temperature Gas-phase Carburization.
Specimen prepared by electropolishing
Un-Filtered
Zero-loss Image
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EFTEM Images from Co-Polymer
Polystyrene and PVDF
Zero loss Image
20 eV Loss Image*
With F
Without F
* Energy of plasmon excitation for Fluorine
OUTLINE
 TRANSMISSION
KIKUCHI DIFFRACTION
(TKD): STEM IN A SEM
EBSD VS TKD
 Bulk material
 Surface
information
 Tilted to 70°
 Interaction volume
30-50 nm
 Thin TEM foil
 Can resolve 3-5 nm
 -20° - 0° tilt
 Exiting surface
structure
70°
Tim Maitland and Scott Sitzman
Scanning Microscopy for Nanotechnology, Springer
René de Kloe - EDAX
WHY USE TKD?
 Improved spatial resolution compared to EBSD: 30-50 nm
⇒ 3-5 nm. Actual resolution will depend on sample
composition and preparation.
Users that have a FIB system together with EDS/EBSD,
can carry out this analysis at practically no extra cost.
Carburized Low-alloy Steel (15 nm/step)
XEDS
OUTLINE

ASTAR SYSTEM
PRECESSION ELECTRON DIFFRACTION (PED)
ADVANTAGES OF ASTAR

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TEM diffraction patterns easier to interpret
Less sensitive to sample thickness variations
More diffraction spots → higher precision
measurements
Automated analysis becomes possible
INDEXING TEM DIFFRACTION PATTERNS
Stereographic projection
(cubic )
111
Pre-calculated templates
Angular step size ~1°
~ 3000 templates
001
1-11
Correlation index
Acquired pattern
ASTAR ORIENTATION MAPPING
Similar results to SEM-EBSD but with much higher spatial
resolution. Down to 1 nm with FEG!
SEM image
Deformed Ta6V
EBSD map
(20-100 nm step size)
TEM map
(1-30 nm step size)
Al (9 nm) –TiN (1 nm)
multilayer system
Al
Phase Map
Orientation Map
ASTAR system could both identify the phases
and orientations.
Note that the Al layers are finely twinned.
ASTAR ORIENTATION MAPPING
Quality Map
Orientation Map
40 nm
Gold nanoparticles
OUTLINE
TEM SAMPLE PREPARATION
FISHIONE NANOMILL MODEL 1040
ADVANTAGES OF NANOMILL
Low energy ion source (up to 2kV Ar)
 Removes amorphous and implanted layers

AS-FIBBED TEM FOIL
High-resolution TEM image of Si showing the effect of Ga
implantation and surface amorphization on phase contrast imaging
AFTER NANOMILLING
Same specimen after Ga implantation and
amorphization removal by the NanoMilling process
SUMMARY
TEM can provide information regarding to
 Structure
 Defects (dislocations, twins, etc.)
 Morphology
 Composition
 Valence state
 Orientation
THANK YOU!