titan themis - cea/leti (english)son...zineb saghi, adeline grenier, daniel lichau 3d chemical...

Zineb Saghi, Adeline Grenier, Daniel Lichau

3D CHEMICAL ANALYSIS OF COMPLEX NANO-DEVICES BY ANALYTICAL ELECTRON AND

ATOM PROBE TOMOGRAPHY

zineb.saghi@cea.fr

Titan Ultimate

Titan Themis

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Electron tomography:

Julien Sorel

Martin Jacob

Nicolas Bernier

Vincent Delaye

CEA-Leti, GrenobleMachine learning:

Francisco de la Pena

University of Lille

Compressed sensing:

Toby Sanders

Arizona State University

Philippe Ciuciu

NeuroSpin, CEA Saclay

Samples:

Rafael Bortolin Pinheiro

Frédéric Mazen

Marie-Claire Cyrille

Gabriele Navarro

Véronique Sousa

CEA-Leti, Grenoble

3DAM partners

Atom probe tomography:

Adeline Grenier

CEA-Leti, Grenoble

Isabelle Mouton

CEA Saclay

Daniel Lichau, Sebastien Millot

Thermo Fisher Scientific

Isabelle Martin

Cameca

Sample preparation:

Audrey Jannaud

Guillaume Audoit

CEA-Leti, Grenoble

CONTRIBUTIONS

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WHY 3D IN SEMICONDUCTOR INDUSTRY?

Composition / Doping

3D TOF-SIMS, APT, STEM-EDX/STEM-EELS

tomography

Dimensions / Morphology

X-ray tomography, serial sectioning by FIB-

SEM, HAADF-STEM tomography

From IMEC

3D architecture

Decreasing size

Increasing complexity

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BASICS OF ELECTRON TOMOGRAPHY

?

1. Acquisition 2. Alignment 3. Reconstruction

A standard electron tomography

experiment:

1. Imaging mode: HAADF-STEM

Incoherent (no diffraction contrast)

Z contrast (I ~ Z2)

2. Automated acquisition: -90°:1°:90°, ~3h,

~500Mb.

3. Automated alignment and reconstruction (~1

day).4mm

1 0 0 0 n m1 0 0 0 n m

Commercial software:•Inspect 3D (FEI)

•TEMography (JEOL)

•3D tomography (Gatan)

•DigiECT (Digisens)

Freeware:

•IMOD

•TomoJ

•TOM software toolbox

•Protomo

•UCSF tomography

•Tomo3D

•ASTRA

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STANDARD ALIGNMENT AND RECONSTRUCTION ALGORITHMS

መ𝑓 = 𝑎𝑟𝑔min𝑓

ℝ𝑓 − 𝑝 22

E. Hanssen, Cellular Imaging: Electron Tomography and Related

Techniques, 2018.

Tilt series alignment

by cross-correlation or with fiducial markers

Reconstruction by SIRT

(simultaneous iterative reconstruction technique)

G. Haberfehlner, 3D nanoimaging of semiconductor devices and materials by electron

tomography, 2013.

Work well if a large number of projections are acquired (tilt increment: ~1-2°)

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EXAMPLE: HAADF-STEM TOMOGRAPHY OF A FLASH-MEMORY CELL

(C. KUBEL ET AL., MICROSC. MICROANAL. 11, 378–400, 2005)

0° HAADF-STEM projection

(contrast inverted)Segmented volume Slice through the reconstruction

Need for spectroscopic modes!

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As Ga

Fe3+

Fe2+

EDX: Energy-dispersive X-ray spectroscopy

EELS: Electron energy loss spectroscopy

SrHAADF-STEM

O

Ti

Atomic chemical mapping of SrTiO3.

Oxidation states in iron oxide nanoparticles.

Atomic chemical mapping of GaAs.Super-X EDX system with 4

detectors

(Fast STEM-EELS: 1000sp/sec)

Spectrum image

Spectrum image

SPECTROSCOPIC MODES

Simultaneous EELS / EDS map of a FinFET (P.

Longo et al., Materials Science in Semiconductor

Processing 65 (2017))

FEI application note

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Titan Ultimate

80-300kV

Image- and probe-corrected

Dual-EELS capabilities

Monochromated source

Titan THEMIS

80-200kV

Probe-corrected

Dual-EELS capabilities

Super-X system with 4

EDX detectors

Simultaneous EELS/EDX

E1 E2 E3 E4 E5

E1 E2 E3 E4 E5

Hyperspectral analysis

Tilt angle (e.g. -90°:10°:90°)

Tilt angle

Reconstruction

(2)

(3)

(1)

(1): stack of hyperspectral datacubes

(2): stacks of elemental maps or chemical phases

(3): 3D reconstruction for each stack.

Tilt angle

ANALYTICAL ELECTRON TOMOGRAPHY

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Issues!

• Electron tomography requires a large number of projections

• Spectroscopic modes require long exposure times and high electron doses (+manual acquisition)

200kV, GL 1.5, Spot size 3, C2 aperture: 30um,

cam. Length: 32mm, probe current: 120pA.

HAADF-STEM: 1024x1024 pixels, pixel size:

0.53nm, frame time: 16.7sec.

STEM-EELS: 100x75 pixels, pixel size: 2.04nm,

dispersion 1eV/ch, SI acquisition time: 18min.

Compromise

• Reduction of the number of projections + advanced alignment and reconstruction algorithms

• Reduction of acquisition time for spectrum images + Multivariate statistical analysis methods

• (Subsampled scanning acquisition + recovery using inpainting techniques)

Projection-Slice Theorem Example of acquisition parameters

CHALLENGES RELATED TO ANALYTICAL ET

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Issues!

• Electron tomography requires a large number of projections

• Spectroscopic modes require long exposure times and high electron doses (+manual acquisition)

200kV, GL 1.5, Spot size 3, C2 aperture: 30um,

cam. Length: 32mm, probe current: 120pA.

HAADF-STEM: 1024x1024 pixels, pixel size:

0.53nm, frame time: 16.7sec.

STEM-EELS: 100x75 pixels, pixel size: 2.04nm,

dispersion 1eV/ch, SI acquisition time: 18min.

Compromise

• Reduction of the number of projections + advanced alignment and reconstruction algorithms

• Reduction of acquisition time for spectrum images + Multivariate statistical analysis methods

• (Subsampled scanning acquisition + recovery using inpainting techniques)

Projection-Slice Theorem Example of acquisition parameters

CHALLENGES RELATED TO ANALYTICAL ET

| 11T. Printemps et al., Ultramicroscopy 160 (2016) 23–34

3-step alignment:

• Cross-correlation between neighboring

projections

• Common line algorithm to get a precise

shift correction in the direction of the tilt

axis.

• Intermediate reconstructions to

precisely determine the tilt axis and

shift correction in the direction

perpendicular to that axis

GUIDAR (GRAPHICAL USER INTERFACE FOR DENOISING ALIGNMENT AND

RECONSTRUCTION)

| 12T. Printemps et al., Ultramicroscopy 160 (2016) 23–34

GUIDAR (GRAPHICAL USER INTERFACE FOR DENOISING ALIGNMENT AND

RECONSTRUCTION)

| 13T. Printemps et al., Ultramicroscopy 160 (2016) 23–34

GUIDAR (GRAPHICAL USER INTERFACE FOR DENOISING ALIGNMENT AND

RECONSTRUCTION)

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Astra toolbox (J. Batenburg)

Compared to commercial packages:- Fast and fully automated

- Optimized for needle-shaped samples

- Works well on datasets with large tilt

increments (5-10°)

T. Printemps et al., Ultramicroscopy 160 (2016) 23–34

GUIDAR (GRAPHICAL USER INTERFACE FOR DENOISING ALIGNMENT AND

RECONSTRUCTION)

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HAADF-STEM ELECTRON TOMOGRAPHY - APPLICATION TO AN EMBEDDED MULTILAYER FIN

30 at. % of Ge in thecenter of the SiGelayers, 50 at. % on thesides

Ge composition map (EDS-STEM)

SiO2

Si

SiGe

• Reference measurements on blanket multilayer :

• RAMAN : ~ 31 at.%

• EDS, Si-K and Ge-L lines, Ge of ~ 28 % at. • EDS, Si-K and Ge-K lines, Ge of ~ 30 % at.

Embedded Multilayer Fins

FIB needle shaped specimen

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Tilt series Aligned tilt series 3D reconstruction (SIRT)

SiGe

Si

SiO2

Acquisition parameters:

• 30 projections from -90° to +90°

• Frame size: 2048x2048 pixels

• Frame time: 20sec

• Pixel size: 133pm

HAADF-STEM ELECTRON TOMOGRAPHY - APPLICATION TO AN EMBEDDED MULTILAYER FIN

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TV

SIRT

Δθ = 5°(27 projections)

Δθ = 10°(13 projections)

Δθ = 15°(9 projections)

TV

SIRT

segmentation

Quantification

Z. Saghi et al., Nano Letters 2011, 11(11), 4666.

R. Leary et al., Ultramicroscopy 2013,131, 70.

TV

SIRT

SIRT: መ𝑓 = 𝑎𝑟𝑔min𝑓

ℝ𝑓 − 𝑝 22

TV: መ𝑓 = 𝑎𝑟𝑔min𝑓

λ 𝑓 𝑇𝑉 + ℝ𝑓− 𝑝 22

with: 𝑓 𝑇𝑉 = 𝛻𝑓 𝑑𝑥

COMPRESSED SENSING RECONSTRUCTION ALGORITHM

Michael Lustig,

http://www.eecs.berkeley.edu/~mlustig/

CS.html

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Issues!

• Electron tomography requires a large number of projections

• Spectroscopic modes require long exposure times and high electron doses (+manual

acquisition)

200kV, GL 1.5, Spot size 3, C2 aperture: 30um,

cam. Length: 32mm, probe current: 120pA.

HAADF-STEM: 1024x1024 pixels, pixel size:

0.53nm, frame time: 16.7sec.

STEM-EELS: 100x75 pixels, pixel size: 2.04nm,

dispersion 1eV/ch, SI acquisition time: 18min.

Compromise

• Reduction of the number of projections + advanced alignment and reconstruction algorithms

• Reduction of acquisition time for spectrum images + Multivariate statistical analysis methods

• (Subsampled scanning acquisition + recovery using inpainting techniques)

Projection-Slice Theorem Example of acquisition parameters

CHALLENGES RELATED TO ANALYTICAL ET

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MULTIVARIATE STATISTICAL ANALYSIS FOR EELS AND EDX

• Number of components estimation :

• Prior knowledge on the observed sample.

• Principal Components Analysis scree-plot.

• Endmembers estimation/extraction :

• Principal Components Analysis

• Independant Components AnalysisDe la Peña et al., Ultramicroscopy, 2011

• Hierarchical clusteringTorruela et al., Ultramicroscopy, 2018

• Bayesian Linear UnmixingDobigeon et Brun, Ultramicroscopy, 2012

• Non-negative Matrix FactorizationShiga et al., Ultramicroscopy, 2016

• Vertex Component AnalysisDobigeon et Brun, Ultramicroscopy, 2012

E1 E2 E3 E4 E5Tilt angle

N TiSpectral

unmixing

Energy axis (eV)

Inte

nsity

Energy axis (eV)

Identification of 3

chemical phases

Inte

nsity

TiAl3GaN TiNStudy of Ti- and Al-Rich

Contact Metallization for

AlGaN/GaN high electron

mobility transistors, T.

Printemps et al. (2017)

Ag nanocube localised

surface plasmon resonances

by STEM-EELS tomography.

Nicoletti et al. Nature 502

(2013) 80-84

NMF is an approach to decomposition

that assumes that the data and the

components are non-negative.

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HAADF-STEM acquisition:

Tilt series: -90°:5°:+90°

Frame size: 2048x2048 pixels

Pixel size : 0.26nm

15sec frame time

EDS-STEM acquisition (using the Super-X system):

Tilt series: -90°:10°:+90°

Datacube size: 193x163x2048

Pixel size : 1nm

10min frame time

Titan THEMIS

80-200kV, probe-corrected

Dual-EELS capabilities

Super-X system with 4 EDX detectors.

Aim of the study

• Conformality of As implantation.

• Dopant depth profiling in 3D.

• Roughness of the sidewalls of

the structure.

Ionized

gaz

Pulsed DC Supply

+

-

-

-

-

-

-

-

- -

+

+

+

Plasma implantation

Collaboration with F. Mazen

HAADF-STEM AND EDX-STEM TOMOGRAPHY OF AS-DOPED SI FIN-SHAPED STRUCTURE

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HAADF-STEM AND EDX-STEM TOMOGRAPHY OF AS-DOPED SI FIN-SHAPED STRUCTURE

50 nm

3D surface roughness of

the left sidewall of the

structure

Mean cluster size: ~15nm3

RMS roughness: ~3nm

xy

HAADF-STEM tomography

(-90°:5°:+90°)

Collaboration with F. Mazen

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SiO2Si AsChemical phase

analysis by NMF

(3 components)

As

SiO2

Si

Si

SiO2

As

As

xy

Chemical phases present: Si, SiO2, As.

As implantation depth: ~20nm

Mean cluster size: ~20 nm3

xyDepth distance (nm)

Inte

ns

ity

(a.u

.)

Collaboration with F. Mazen

As

SIRT

TV

HAADF-STEM AND EDX-STEM TOMOGRAPHY OF AS-DOPED SI FIN-SHAPED STRUCTURE

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GE-RICH GE2SB2TE5 (GST) FOR PHASE CHANGE MEMORY (PCM) APPLICATIONS

TOP ELECTRODE

PCM

HEATERACTIVE

VOLUME

X

Y

Example of an industrial PCM device

From: Phase change materials: science and

applications, S. Raoux and M. Wuttig, Springer

Verlag, New York, 2009.

Current challenge: PCM memory

devices stability is challenged at high

temperature (automotive applications).

SET RESET

0 100 200 300 40010

-3

10-1

101

103

105

GST

GST+Ge30%

GST+Ge35%

GST+Ge40%

GST+Ge45%

GST+Ge Opt.

RE

SIS

TIV

ITY

[c

m]

TEMPERATURE [°C]

Ge-rich GSTTc~380°C

Ge2Sb2Te5

Tc~170°C

Increase of Ge at. %

Increase of crystallization temperature (Tc)Collaboration with V. Sousa, G. Navarro and M-C. Cyrille

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Different grain size after annealing

can impact the programming

reliability of the PCM device

Large grains Finer crystalline

structure

SET operation (i.e. crystallization)

becomes more reliable thanks to a

finer crystalline structure:

→ A lower resistance is achieved

Ge-rich GST crystallisation Phase separation GST & Ge

GE-RICH GE2SB2TE5 (GST) FOR PHASE CHANGE MEMORY (PCM) APPLICATIONS

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Capping

SiO2

SiN

GST /

Ge

HAADF-STEM AND STEM-EELS TOMOGRAPHY OF GE-RICH GST MATERIALS ANNEALED AT

450°C

Titan THEMIS

80-200kV, probe-corrected

Dual-EELS capabilities

Super-X system with 4 EDX detectors.

Acquisition parameters:

200kV, GL 1.5, Spot size 3, C2 aperture: 30um,

cam. Length: 32mm, probe current: 120pA, mag

160kx.

HAADF-STEM (-90°:5°:+90°): 1024x1024 pixels,

pixel size: 0.53nm, frame time: 16.7sec.

STEM-EELS (-90°:10°:+90°): 100x75 pixels, pixel

size: 2.04nm, exposure time: 0.1sec (450eV,

1eV/ch), SI acquisition time: 18min.Collaboration with V. Sousa, G. Navarro and M-C. Cyrille

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1

2

3

4

0 . 0 5 µ m50 nm

<

1

2

3

4

N K-edge: 401eV

Sb M4,5-edge: 528 eV

O K-edge: 532 eV

Te M4,5-edge: 572 eV

Ge L2,3-edge: 1217 eV

Si K-edge: 1839 eV

600 800 1000 1200 1400 1600

2000

4000

6000

8000

10000

12000

14000

16000

18000

Inte

nsity

(a.u

.)

eV

GST

Ge

0

Chemical phase

analysis by VCA

(6 components)

Collaboration with V. Sousa, G. Navarro and M-C. Cyrille

HAADF-STEM AND STEM-EELS TOMOGRAPHY OF GE-RICH GST MATERIALS ANNEALED AT

450°C

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GSTGe

xyxz xzxy

Cross-correlation alignment

SIRT reconstruction

Collaboration with V. Sousa, G. Navarro and M-C. Cyrille

HAADF-STEM AND STEM-EELS TOMOGRAPHY OF GE-RICH GST MATERIALS ANNEALED AT

450°C

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WAVELET-BASED COMPRESSED SENSING ALGORITHM

SIRT: መ𝑓 = 𝑎𝑟𝑔min𝑓

ℝ𝑓 − 𝑝 22

TV minimization: መ𝑓 = 𝑎𝑟𝑔min𝑓

λ 𝑓 𝑇𝑉 + ℝ𝑓− 𝑝 22 , with: 𝑓 𝑇𝑉 = 𝛻𝑓 𝑑𝑥

Wavelet-based CS: መ𝑓 = 𝑎𝑟𝑔min𝑓

λ Ψ𝑓 1 + ℝ𝑓− 𝑝 22

Collaboration with Neurospin, CEA Saclay.

HAADF-STEM tilt series Ge (blue) and GST (red) tilt series

isotropic anisotropic

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• HAADF-STEM electron tomography: ok for 3D morphological analysis but we want more.

• “Dopant” diffusion & activation studied by analytical ET.

• Analytical ET now possible with recent developments in spectral analysis and reconstruction algorithms.

• Even if EDS & EELS are now sensitive enough to detect “dopant” in 3D structures, quantification with

standard methods & low SNR remains challenging.

Perspectives

• MSA techniques for low dose EDX and EELS

• EDX & EELS quantification in 2D & 3D

• Correlation with other techniques (APT, SIMS…)

SUMMARY ON ANALYTICAL ET

| 30

APT holderET holder

2 mm

Sup

po

rt t

ipA

nal

ysis

vo

lum

e

CORRELATIVE ET/APT

Same sample is prepared by FIB and mounted onto ET and APT holders

2 µm 2 µm

2

µm

Devices to be

analysed2 µm 200 nm 200 nm

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ATOM PROBE TOMOGRAPHY BASICS

P O

R

Xtip, Ytip Xdet, Ydet

L (L≫R)(m+1) R

Magnification (lateral scaling): M= 𝐿

𝑚+1 𝑅

depends on – unknown - radius evolution during analysis.

Depth is calculated from sequence: zi = zi-1+dzi with dzi = 𝑉i.𝑀

2

𝑄𝑑𝑒𝑡.𝑆D

(𝑄𝑑𝑒𝑡 : detector efficiency, 𝑆D : detected surface, 𝑉i: applied voltage)

Radius parameter is estimated typically either from:

o Applied voltage 𝑅 𝑧 =𝑉 𝑧

𝐸.β

(E: evaporation electric field, β: instrument’ field factor)

o Tip cone shank angle α

o Tip profile, e.g. measured from TEM image

APT reconstruction basics

R

α

Time Of Flight measure Continuous voltage +

electric or laser impulsion

(V ≈ 3-15 kV, T ≈ 20-80 K, E> 10 V/nm)

APT acquisition

3D spatial

atom locationsTOF mass spectrometer Detector impacts

APT

reconstruction

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APT RECONSTRUCTION ARTEFACTS

Local magnification effects

Presence of two phases

Local radius variation

with different fields of evaporation

Inhomogeneous distribution of the electrostatics field Preferential evaporation phenomena

L

(m+1).R M =

V

β.E R =

Ion trajectory aberrations

Si

STEM HAADF

SiO2

50 nmESiO2 = 1,25 ESi

Si

ETiN = 1,15 ESi

EHfO2 = 1,45 ESi

Si

TiN

HfO2

B. Gault et al.

Si

TiN

HfO2

20 nm

Density

correction

Reconstructions is less distorted -> is the quantification reliable?

Heterogenous structures with non-uniform

evaporation lead to:

- variable local magnification

- distortions of reconstructed volume

- abnormal atom density variations

- species crossovers.

D. J. Larson et al.

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10 nm 50 nm

Si

SiO2

3D electron tomography

reconstruction of the 45 nm

device after segmentation.

3D APT reconstruction of the

45 nm device

Density corrected algorithm

+

3D boron distribution

inside the gate with

minimal distortions.

Si

SiO2

B

O

Si

B

CORRELATIVE ET/APT RESULTS

Improvement of APT reconstruction using the combination of electron tomography results with

density corrected APT algorithm.

A.Grenier, S. Duguay, F. Vurpillot et al, APL, 106, 213202 (2015)

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Comparison between the reconstructions of GaN/InGaN/AlGaN multilayers obtained

from (a) the standard method and (b) the two-step, interface-flatness driven, process.

ATOM PROBE TOMOGRAPHY – ARTEFACT CORRECTION BY AN INTERFACE-FLATNESS

PROCESS

F. Vurpillot et al., Ultramicroscopy 132 (2013), 19.

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ATOM PROBE TOMOGRAPHY – CORRELATION BY RIGID BODY TRANSFORMATION

The reconstruction algorithm uses the initial tip

radius (R0) and shank angle (α), which is the angle

between a tip axis and a tip surface. Image

compression factor and detection efficiency are

considered to have a constant value of 1.6 and 62%

respectively

I. Mouton et al., Ultramicroscopy 182 (2017), 112.

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Indium

concentration

Low Indium

3D iso

STEM HAADF

Low Indium reference 3D volume

(reconstructed from 2D TEM image)

Affine registration

ATOM PROBE TOMOGRAPHY – CORRELATION BY NON-RIGID BODY TRANSFORMATION (AVIZO)

Non-rigid registration

EDX/EELS-STEM

tomography?

| 37

Phase Separation in an Alnico 8 Alloy.

Guo et al., Microsc. Microanal. 22, 1251 (2016)

EDX-STEM

tomographyAPT EDX-STEM

tomographyAPT

Nanomagnetic properties of the meteorite cloudy zone.

J.F. Einsle et al., PNAS 49, 115 (2018)

Ni

Fe

ATOM PROBE TOMOGRAPHY AND EDX-STEM TOMOGRAPHY

| 38

ATOM PROBE TOMOGRAPHY AND EDX/EELS-STEM TOMOGRAPHY

Future trends:

- Correction of distortions in the APT volumes, by using the AET

volumes as prior knowledge.

- Combination of large field-of-view AET volumes with APT sub-

volumes (small precipitates resolved, and low concentration

dopants detected).

- Use of APT reconstruction to validate the quantification

methods developed by the AET community.

EELS/EDX-STEM tomography:

Non-destructive, large fields of view, high spatial fidelity,

limited spatial resolution (few nms), LLD ~1×1020 at.cm-3,

quantification methods not fully developped.

APT:

Destructive, small fields of view, limited spatial fidelity, high

spatial resolution, LLD ~5×1018 at.cm-3, quantitative method.

| 39

Thank you for your attent ion!