F From STEM EELS to multi dimensional and STEM EELS t lti di i - - PowerPoint PPT Presentation

Taipei, November 22, 2011

F STEM EELS t lti di i l d From STEM‐EELS to multi‐dimensional and multi‐signal electron microscopy

Christian Colliex L b i d h i d S lid ld 10 Laboratoire de Physique des Solides, Bldg 510 Université Paris Sud, 91405, Orsay, France christian colliex@u‐psud fr christian.colliex@u‐psud.fr

Outline Outline

Signals, instrumentation and methods for STEM EELS Atomically resolved elemental and bonding maps Mapping plasmons and EM fields When electrons and photons team up

Electron Matter interactions Electron – Matter interactions

Secondary Secondary Event vs. Primary Event

Transmission Electron Microscopy ‐ A Textbook for Material Science David Williams and Barry Carter, Fig. 1.3, page 7.

Working modes for an transmission electron microscope

EDX spectroscopy Electron source (0.5 à 2eV) d ( ) Diffractions

• bject (gonio)

condensers anode(s) a few 100kV HREM imaging

• bject (gonio)

Objective lens

Nanolaboratory : Specific specimen holders and stages

Intermediate lenses Projector lens Hologram

holders and stages

Electron Energy Loss Spectroscopy (EELS) Hologram Energy filtered imaging Magnetic prism Energy filtered imaging p

1980 20

STEMs with EELS analysers at Orsay

1980 ‐ 20xx 2008 ‐ 2011

y

2011 ‐ 20xx

VG HB 501 NION UltraSTEM 100 NION UltraSTEM 200

20 nm

EELS spectrum

EELS spectrum‐image at Orsay

A B

y

HADF image

450 400 350 300 Energy Loss (eV)

Magnetic spectrometer

Spectrum 0.5 to 0.8 eV 1 ms to 5 s SPECTRE LIGNE

SPECTRUM LINE

Magnetic spectrometer

E E - E

• C

amera CCD

Specimen

HADF detectors

A

Specimen Probe

0- (nm)

• 0.1 to 1nA
• in 0.5 to 1 nm

Scanning coils

I I I I

2 0 300 3 0 400

40- (nm)

Field emission gun

100 keV

250 300 350 400

Energy Loss (eV)

B

Multi‐dimensional microscopy in a composite space (x,y position, E energy and t time)

x

(x,y position, E energy and t time)

x y E

E

1D EELS t

x

0D : bit of information 1D : EELS spectrum

x y

3D : spectrum image data cube

y E (or x)

data cube 2D t li

y E

2D : spectrum line

• r E‐ filtered image

Use of C correctors to reduce Use of Cs correctors to reduce probe size or to increase probe current : i) <1 Å probe size at 100 kV, Å <0.7 Å at 200 kV ii) 200 pA of current in a 1.4 Å probe iii) 1 nA current in a 2 3 Å probe iii) 1 nA current in a 2.3 Å probe

Orsay Nion U‐STEM 100 acceptance tests

New UltraSTEM for aberration‐corrected nanoanalysis (delivered in Orsay in 2008) (delivered in Orsay in 008)

The column is built from modules that all have the

a b

modules that all have the same mechanical interface and are 100% interchangeable. interchangeable. Each module has triple magnetic plus acoustic g p shielding. Emphasis is on small probe formation and efficient coupling into detectors. Everything including sample exchange can be t d t l

• perated remotely.

Nion UltraSTEM 200 performance at Orsay

Imaging molecules containing heavy atoms (a) (b) (c)

• 0. 5 nm
• 0. 5 nm

1 nm 1 nm

(d) (d)

2 nm 2 nm 2 nm 2 nm

polyoxometalate (POM; As2W20O70Co(H2O)) molecules grafted on C‐SWNT courtesy A. Gloter, Orsay (2011)

BN monolayer with impurities imaged by MAADF

Result of DFT calculation overlaid on Matt Chisholm’s experimental MAADF image

C ring is

N

C ring is deformed

Cx6 O N B C O O

Longer

B C O

Longer bonds

C Na

adatom

C

Si substituting for C in monolayer graphene

Si 2 Å Si Si Si N Si Si Si Si

M di l l d k fi ld (MAADF) i Si at and near topological defects Si in topologically correct graphene Si at graphene’s edge Medium angle annular dark field (MAADF) images. Nion UltraSTEM100 at ORNL, 60 kV. Image courtesy Matt Chisholm, ORNL, sample courtesy Venna Krisnan and Gerd Duscher, U. of Tennessee.

Si substituting for C: 2 structures are possible

Si 2 Å Si Si Si N Si Si Si Si

Si in defect‐free graphene strains (and Si in defective, but less strained graphene is buckles) the foil. (courtesy Matt Chisholm) more stable. (15 images added together, no

• ther processing,

courtesy Juan‐Carlos Idrobo)

EELS spectroscopy : spectral domains Phonons Plasmons Absorption edges IR visible UV X

2.5 ) x 10 6)

Low losses

C l

1.5 2.0 ts number)

Low losses

Core losses CK

1.0 sity (count 0.5

Energy loss (eV)

Intens x50 x106

MnL2,3

100 200 300 400 500 600 700

EELS: Involved electron populations and associated transitions

Energy (eV)

CB. O ‐K

0^3 40 50 60 0^3

EF VB.

x 10 10 20 30 40 x 10

120

Plasmons IT O 1 L2,3

eV 10 520 530 540 550 560 570 580 590 600 610 eV

K

60 80 100

IT TM 2p O 1s

0^3 200 250 300 350 0^3

TM L2,3 TM L2,3

20 40 5 10 15 20 25

• 530 eV
• 710 eV

2

x 10 50 100 150 x 10

eV eV

• 725 eV

eV 695 700 705 710 715 720 725 730 735 eV

EELS gives informations on the electronic structure

EELS spectroscopy : spectral domains

Core energy‐loss domain Low energy‐loss domain

CK CK

MnL2,3

Core energy loss domain Low energy loss domain

Plasmon modes 250 300 400 350 250 300 400 350 Energy loss (eV) 690 630 650 670 Energy loss (eV)

i h hi h h

10 20 30 40 Energy loss (eV)

Map with high accuracy the nature, the position and bonding

• f the atoms responsible for the

structural properties Map different physical parameters, electronic,

• ptical or magnetic,

which are especially important structural properties

• f real materials

(defects, interfaces, nanomaterials) R i i i h which are especially important for electronic industries Requires instruments adapted Requires instruments with best spatial and energy resolutions (0.1 nm, 0.1 eV) to measure the properties of interest at the relevant scale Towards the nanolaboratory

In all cases, develop the theory for interpreting spectroscopical data i e

Towards the nanolaboratory

spectroscopical data, i.e. a physics of excited states

Absorption Absorption edges edges domain domain : Absorption Absorption edges edges domain domain : : three three types of information types of information

Identification of elements

CK

Elementary quantification

250 300 400 350



Energy loss (eV)

 Study of the unoccupied electron states distribution

Quantitative elemental analysis Q y

Characteristic signal : proportional to the number of atoms per unit area for the element detected in

BK

S

area for the element detected in the analysed area

CK



S = ct. I N 

NK

sity

Atomic concentration ratios:

NA SA B

Intens

NB

=

SB A

200 300 400 Energy loss (eV)

EELS core‐level spectroscopy: EELS core level spectroscopy: elemental and bonding maps with atomic resolution resolution

• 1. Individual atoms
• 1. Individual atoms
• 2. Crystalline structures and interfaces
• 3. Application to Tunnel ElectroMagneto
• 3. Application to Tunnel ElectroMagneto

Resistance – TEMR

Single atom identification (signal/noise criteria)

Peapods : Gd@C82@SWCNT Element selective single‐atom imaging A HREM i A : HREM image B : Schematic presentation C : Superposed maps of the Gd N45 and C K signals extracted from a 32x128 pixels spectrum image (C in 32x128 pixels spectrum‐image (C in blue, Gd in red)

• K. Suenaga et al., Science (2000)

STEM imaging of peapods at 30 and 60 kV with Delta STEM imaging of peapods at 30 and 60 kV with Delta corrector

30kV 60kV

Damage drastically reduced at 30kV

Courtesy Suenaga, Sawada & Sasaki (2010)

Single atom imaging by STEM‐EELS at low voltage with the g g g y g delta corrector

Endohedral fullerenes M@C82 (M= La, Ce, Er) Iizumi and Okazaki

Atom by atom labeling at 60kV y g

Courtesy K. Suenaga (AIST, Tsukuba, 2010)

Valence state identification of individual atoms La3+ Ce3+ La3+ in LaCl3 Ce3+ in CeCl3 Ce4+ in CeO2

Courtesy K. Suenaga (AIST, Tsukuba, 2010)

EELS spectrum‐imaging across interfaces

S C C lli N t N&V (2007) See C. Colliex, Nature N&V (2007) HAADF micrograph

Elemental maps recorded with NION UltraSTEM at Orsay ( t L B h 2011) (courtesy Laura Bocher, 2011)

Spectroscopic imaging of LMO down the pseudocubic <110> axis. The sketch shows the projected structure of LMO down this direction. In green, the O K edge image; in blue the simultaneously acquired Mn L2,3 image and in red the La M4,5 image. The RGB overlay

• f the three elemental maps is also shown.

From M. Varela et al. to be published in MRS bulletin 01/2012

• D. Muller et al. Science 319 (2008) 1073)

High resolution Z contrast image of a LCMO/YBCO/LCMO heterostructure The inset High resolution Z‐contrast image of a LCMO/YBCO/LCMO heterostructure. The inset marks the region where an EELS spectrum image was acquired, along with the simultaneous ADF signal. (b) O K, Mn L2,3, Ba M4,5 and La M4,5 atomic resolution images (c) RGB overlay of the Mn (red) La (green) and Ba (blue) images in (b) The

• images. (c) RGB overlay of the Mn (red), La (green) and Ba (blue) images in (b). The

sketch shows the interface structure. From M. Varela et al. to be published in MRS bulletin 01/2012

Ferroelectric control of spin polarization (Tunnel ElectroMagneto Resistance – TEMR) (Tunnel ElectroMagneto Resistance – TEMR)

 tunnel junctions with ferromagnetic electrodes for large nonvolatile control of carrier spin polarization by switching ferroelectric polarization

• ultrathin BTO ferroelectric
• half‐metallic LSMO as spin detector
• Fe electrode

p

• NGO: substrate

Information provided from STEM/EELS analyses

Garcia V. et al. Science DOI: 10.1126/science.1184028

* Structural quality of the film growth and the interfacial area * Termination planes at the interfaces * Oxidation states of the TM at the atomic scale d d d h l l h / f In order to understand the electromagnetic coupling at the FE/FM interface Garcia V. et al. Science (2010)

Ferroelectric control of spin polarization

V Garcia et al (Thales/CNRS Palaiseau LPS Orsay U Cambridge)

• V. Garcia et al (Thales/CNRS Palaiseau, LPS Orsay, U. Cambridge)

BTO Fe LSMO NGO

10 nm

BTO Fe

[001] [110]

1 nm

[001]

USTEM data courtesy A. Gloter & L. Bocher

TMR (H) measured for reversed bias polarities

• n the ferroelectric junction

y

• L. Bocher et al. submitted (2011)

BaTiO3/Fe interface

i)

• ne possible structure model model

ii) image simulation iii) and iv) HAADF experimental images ) ) p g iv) elemental profiles

Courtesy L. Bocher & A. Gloter JOM 62 (12/2010) 53‐57

STEM imaging the interface BTO‐Fe

HAADF BF

Atomic structure at the interface : comparison experiment, models and simulations

• L. Bocher et al. submitted (2011)

Elemental composition and Fe EELS L23 fine structures across the interface

Presence of oxidized Fe (in the Fe++ as well as in the Fe+++ state) over one atomic layer at the interface

• L. Bocher et al. submitted (2011)

Modelling the interface and electronic structure calculations

DFT calculations

• f the spin polarisation
• L. Bocher et al. submitted (2011)

Orsay STEM

Trends of the accessible

1

0.2

2

90s

performance in terms of spatial and spectral resolution (updated in 2010)

1 1

EFTEM 70s Cs correctors

(updated in 2010)

0.3 0.3

V)

IBM STEM 90s

Must be accompanied with a parallel development in data processing and modelization tools (propagation of a

∆E (eV

modelization tools (propagation of a sub‐angström electron probe across a thin specimen, physics of the inelastic scattering, calculation of electron

0.1 0.1

Monochromators 80 00 U‐STEM 2010

g, density of states…)

1 0.2 2

80s‐00s

0.1

2010

Where are we now ?

∆x (nm)

Mapping plasmons and EM fields Mapping plasmons and EM fields

4D ( 4D (x,y,E,t x,y,E,t) Spectrum ) Spectrum‐imaging imaging mode mode

e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐

Improved energy resolution (0 2 eV) (0.2 eV)

Sample / i l

at each pixel

• 50 spectra/pixel
• 3 ms/spectrum

d l ti

+ HAADF signal

• deconvolution

New possibilities for studying the low energy‐loss domain

Deconvolution techniques open the way to investigating nanophotonics with electrons 2.25 eV

U.V. I.R.

1.8 eV 1 15 eV

Increase in ΔE (f 0 35 V t 0 25 V)

1.15 eV 2 4 6 Energy loss (eV)

(from 0.35 eV to 0.25 eV) Cut‐off of zero loss signal at 0.9 eV (IR)

New technical possibilities (A. Gloter, A Douiri, M. Tencé)

Higher signal‐to‐background ratio

Mapping surface plasmon resonances

• f triangular silver nanoprisms

B

• f triangular silver nanoprisms

78 nm edge long 78 nm edge long nanoprism nanoprism

A B C D

Energy map of the “tip” mode

• J. Nelayah et al. Nature Physics, 3, 348‐353 (2007)

EELS simulations of triangular Ag nanoprisms

(courtesy J. Garcia de Abajo, Madrid)

1.9 eV 2.9 eV

0.8 1.0

3.4 eV

0.2 0.4 0.6 0.0

• 100 Kv electrons
• 78 nm long and 10 nm

thick Ag prism g p

Modes in an Ag nanoantenna (aspect ratio L/r increases)

(coll Cambridge Stuttgart courtesy P Midgley) 1.2eV 1.4eV

1.6eV

(coll. Cambridge‐Stuttgart, courtesy P. Midgley) 1.2eV 1.4eV

1.6eV

2 3

1 8 V 2 0 V 2 2 V 2 4 V 1.8eV 2.0eV 2.2eV 2.4eV

4 5 6

2 6 V EFTEM i 2.6eV 2.8eV 3.0eV 3.2eV EFTEM series on SESAM machine 660 nm Ag nanorod

7

0.2eV slit width

Silver nanoantennas EELS (2)

Nano Lett 11, 1499 (2011)

Experiments versus simulations

(DDA of |Ez|2 at 60 nm above antenna)

When electrons and photons team up « Multi‐signal microscopy »

« When electrons and photons and photons team up »

by F.J. Garcia de Abajo (Nature 462 (2009) 861)

Light detection (inserting a parabolic mirror within the VG pole piece) VG pole piece)

home-made cold stage + light d t t (L Z l S detector (L. Zagonel+ S. Mazzucco + M. Kociak) Monochromatic electron beam Electron Induced Radiation Emission (Cathodoluminescence) Electron Energy-Loss

Absorption by EELS

gy Spectrum

Emission by CL Absorption by EELS y

2 patents (licensing opportunities)

2D photon emission spectral‐ emission spectral‐ imaging

• Spatial sampling: 0.7 nm
• S

t l li 2 ( 8 V)

VG HB501

• L. Zagonel, M. Kociak et al., NanoLetters 2011
• Spectral sampling: 2 nm (ca 8 meV)
• Individual QD optical properties revealed!

Spectral Imaging with electrons

EELS CCD camera EELS spectrometer EELS scintillator HAADF EELS aperture EELS scintillator

c

Sample Secondary Electrons CL Spectrometer Obj ti l CL Mirror CL Spectrometer

CL PM

Electron gun tip Scan coils Objective lens

• M. Kociak et al., patents pending
• L. Zagonel, A. Losquin et al.,

unpublished,

• Absorption and emission on the same object
• @ nm resolutions..

p

,

Absorption and Emission

multi-detection: HADF+ EELS + EIRE (CL)

first proof of principle for simultaneous EELS/EIRE

symmetry of the modes, modal decomposition?

CL

Energy 2.2 eV

EELS

(radiative and non

CL

(only radiative modes)

radiative modes)

No energy resolution limitation by the PSF detection system:

• ptical spectroscopy at a true nanometer scale

Nature, 17 december 2009

and now?

With synchronised light injection (cf Zewail’s group at UCLA) New spectroscopies synchronizing electrons and photons (injecting light)

• (i) electron energy‐GAIN spectroscopy
• (ii) dynamics of excited states
• (ii) dynamics of excited states

The most The most recent textbook on the market…

MRS Bulletin, january 2012

• n

“Spectroscopic Imaging in Electron Microscopy”

Ed S P k & C C lli

• Eds. S. Pennycook & C. Colliex

Invited contributions : Invited contributions :

• G. Botton, McMaster, Canada

M Varela et al ORNL USA and Madrid Spain

• M. Varela et al. ORNL, USA and Madrid, Spain
• M. Kociak, Orsay, France & J. Garcia de Abajo, Madrid, Spain
• K. Suenaga et al. AIST, Japan

L J All t l M lb A t li L.J. Allen et al. Melbourne, Australia

• M. Aronova & R.D. Leapman, NIH, USA

The Orsay team enabling the future (june 2011)

http://www.lps.u‐psud.fr/stemlps

Thanks to all my colleagues at LPS Orsay Thanks to all my colleagues at LPS Orsay Guillaume Boudarham, Laura Bocher N th li B Al d Gl t Nathalie Brun, Alexandre Gloter, Mathieu Kociak, Katia March, Stefano Mazzucco, Claudie Mory, Odile Stéphan, Marcel Tencé, Almudena Torres-Pardo, Mike Walls, Luis Zagonel and Alberto Zobelli from LPS Orsay, France Thanks to CNRS CNRS and to EC funded programs EU Thanks to CNRS CNRS and to EC funded programs EU SPANS et ESTEEM and to all our partners who have submitted scientific issues to solve and suited specimens

Thank you very much for your attention