TRANSMISSION ELECTRON MICROSCOPY

TRANSMISSION ELECTRON MICROSCOPY Danqi Wang Swagelok Center for Surface Analysis of Materials (SCSAM) Case Western Reserve University 1 OUTLINE  ...
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TRANSMISSION ELECTRON MICROSCOPY Danqi Wang Swagelok Center for Surface Analysis of Materials (SCSAM) Case Western Reserve University

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OUTLINE   

SCSAM TEM Instrument Introduction Scanning TEM   



Imaging XEDS EELS

TEM

Bright-field/Dark-field Imaging  High-resolution Imaging  Diffraction  Energy-filtered TEM Transmission Kikuchi Diffraction/ASTAR system 





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

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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. 8

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 9

What do can we learn?  

 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 18

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   



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!

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