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Taipei, November 22, 2011
F STEM EELS t lti di i l dFrom STEM‐EELS to multi‐dimensional and multi‐signal electron microscopy
Christian ColliexL b i d h i d S lid ld 10Laboratoire de Physique des Solides, Bldg 510Université Paris Sud, 91405, Orsay, France
christian colliex@u‐psud frchristian.colliex@u‐psud.fr
OutlineOutline
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 interactionsElectron – Matter interactions
SecondarySecondary Event
vs.
Primary Event
Transmission Electron Microscopy ‐ A Textbook for Material ScienceDavid 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
object (gonio)
condensers
anode(s) a few 100kV
HREM imaging
object (gonio)
Objective lens
Nanolaboratory :Specific specimenholders and stages
Intermediate lenses
Projector lensHologram
holders and stages
Electron Energy LossSpectroscopy(EELS)
Hologram
Energy filtered imagingMagneticprism Energy filtered imagingp
1980 20
STEMs with EELS analysersat Orsay
1980 ‐ 20xx
2008 ‐ 2011
y
2011 ‐ 20xx
VG HB 501
NION UltraSTEM 100
NION UltraSTEM 200
20 nm
EELS spectrumEELS spectrum‐image
at Orsay
AB
y
HADF image
450400350300Energy Loss (eV)
Magnetic spectrometerSpectrum 0.5 to 0.8 eV
1 ms to 5 s
SPECTRE LIGNESPECTRUM LINE
Magnetic spectrometerE
E -E
o
o
CameraCCD
Specimen
HADF detectorsA
Specimen
Probe
0-
(nm)• 0.1 to 1nA• in 0.5 to 1 nm
Scanning coils
I I I I2 0 300 3 0 400
40-
(nm)
Field emission gun
100 keV250 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
yE E1D EELS t
x
0D : bit of information 1D : EELS spectrum
x
y 3D : spectrum imagedata cube
yE (or x)
data cube
2D t liy
E
2D : spectrum lineor E‐ filtered image
Use of C correctors to reduceUse of Cs correctors to reduceprobe 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 probeiii) 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 bmodules that all have the same mechanical interface and are 100% interchangeable.interchangeable.
Each module has triple magnetic plus acoustic g pshielding.
Emphasis is on small probe formation and efficient coupling into detectors.
Everything including sample exchange can be
t d t loperated remotely.
Nion UltraSTEM 200 performance at
Orsay
Imaging molecules containing heavy atoms
(a) (b) (c)
0.5 nm0.5 nm
1 nm1 nm
(d)(d)
2 nm2 nm 2 nm2 nm
polyoxometalate (POM; As2W20O70Co(H2O)) molecules grafted on C‐SWNTcourtesy 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
Cx6O
N
B C OO
Longer
B C O
Longer bonds
CNa adatom
C
Si substituting for C in monolayer graphene
Si
2 Å
Si
Si
SiN
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’sedge
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
NSi
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 other processing, courtesy Juan‐Carlos Idrobo)
EELS spectroscopy : spectral domains
Phonons Plasmons Absorption edges
IRvisible
UV X
2.5
) x 1
0 6 )
Low losses C l
1.5
2.0
ts n
umbe
r) Low losses Core lossesCK
1.0
sity
(cou
nt
0.5Energy loss (eV)
Inte
ns
x50 x106
MnL2,3
0 100 200 300 400 5000 600 700
EELS: Involved electron populations and associated transitions
Energy (eV)
CB. O ‐K
0^3
40
50
60
0^3
EFVB.
x 10
10
20
30
40
x 10
120 PlasmonsIT
O 1
L2,3 eV
10520 530 540 550 560 570 580 590 600 610
eVK
60
80
100IT
TM 2p
O 1s
0^3 200
250
300
350
0^3
TM L2,3TM L2,320
40
0 5 10 15 20 25
-530 eV
-710 eV2 x
100
50
100
150
x 10eVeV -725 eV
eV
0695 700 705 710 715 720 725 730 735
eV
EELS gives informations on the electronic structure
EELS spectroscopy : spectral domains
Core energy‐loss domainLow energy‐loss domain
CKCK MnL2,3
Core energy loss domainLow energy loss domain
Plasmon modes
250 300 400350250 300 400350Energy loss (eV)
690630 650 670Energy loss (eV)
i h hi h h
0 10 20 30 40Energy loss (eV)
Map with high accuracy the nature,the position and bonding
of the atoms responsible for thestructural properties
Map different physical parameters, electronic, optical or magnetic,
which are especially important structural properties of 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 interestat the relevant scale
Towards the nanolaboratoryIn all cases, develop the theory for interpreting
spectroscopical data i eTowards the nanolaboratoryspectroscopical data, i.e. a physics of excited states
AbsorptionAbsorption edgesedges domaindomain ::Absorption Absorption edgesedges domaindomain : : threethree types of informationtypes of information
Identification of elements
CK
Elementary quantification
250 300 400350
Energy loss (eV)
Study of the unoccupied electron states distribution
Quantitative elemental analysisQ y
Characteristic signal : proportionalto 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
NKsity
Atomic concentration ratios:
NA SA B
Inte
ns
NB=
SB A
200 300 400Energy loss (eV)
EELS core‐level spectroscopy:EELS core level spectroscopy:elemental and bonding maps with atomic
resolutionresolution
1. Individual atoms1. Individual atoms2. Crystalline structures and interfaces3. Application to Tunnel ElectroMagneto3. Application to Tunnel ElectroMagneto
Resistance – TEMR
Single atom identification (signal/noise criteria)
Peapods :
Gd@C82@SWCNT
Element selective single‐atom imaging
A HREM iA : HREM image
B : Schematic presentation
C : Superposed maps of the Gd N45 and C K signals extracted from a 32x128 pixels spectrum image (C in32x128 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 DeltaSTEM 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 voltagewith the g g g y gdelta corrector
Endohedral fullerenes M@C82 (M= La, Ce, Er)Iizumi and Okazaki
Atom by atom labeling at 60kVy g
Courtesy K. Suenaga (AIST, Tsukuba, 2010)
Valence state identification of individual atoms
La3+ Ce3+
La3+ in LaCl3Ce3+ in CeCl3Ce4+ in CeO2
Courtesy K. Suenaga (AIST, Tsukuba, 2010)
EELS spectrum‐imagingacross interfaces
S C C lli N t N&V (2007)See C. Colliex, Nature N&V (2007)
HAADF micrograph
Elemental maps recorded withNION 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 of 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 insetHigh 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) Theimages. (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 / fIn order to understand the electromagnetic coupling at the FE/FM interface
Garcia V. et al. Science (2010)
Ferroelectric control of spin polarizationV Garcia et al (Thales/CNRS Palaiseau LPS Orsay U Cambridge)V. Garcia et al (Thales/CNRS Palaiseau, LPS Orsay, U. Cambridge)
BTOFe LSMO NGO
10 nm
BTOFe
[001]
[110]
1 nm
[001]
USTEM data courtesy A. Gloter & L. BocherTMR (H) measured
for reversed bias polaritieson the ferroelectric junction
yL. Bocher et al. submitted (2011)
BaTiO3/Fe interface
i) one possible structure model modelii) image simulationiii) and iv) HAADF experimental images) ) p giv) elemental profiles
Courtesy L. Bocher & A. GloterJOM 62 (12/2010) 53‐57
STEM imaging the interface BTO‐Fe
HAADFBF
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 atthe interface
L. Bocher et al. submitted (2011)
Modelling the interface and electronic structure calculations
DFT calculationsof the spin polarisation L. Bocher et al. submitted (2011)
Orsay STEMTrends of the accessible
10.2 2
90sperformance in terms of spatial and spectral resolution
(updated in 2010)
1 1
EFTEM70s
Cs correctors(updated in 2010)
0.3 0.3
V)
IBM STEM90sMust be accompanied with a parallel
development in data processing and modelization tools (propagation of a
∆E (eVmodelization tools (propagation of a
sub‐angström electron probe across a thin specimen, physics of the inelasticscattering, calculation of electron
0.1 0.1Monochromators
80 00U‐STEM2010
g,density of states…)
10.2 2
80s‐00s
0.1
2010
Where are we now ?∆x (nm)
Mapping plasmons and EM fieldsMapping plasmons and EM fields
4D (4D (x,y,E,tx,y,E,t) Spectrum) Spectrum‐‐imagingimaging modemode
e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐ e‐e‐ e‐ e‐ e‐ Improved
energyresolution(0 2 eV)(0.2 eV)
Sample
0 / i l
at each pixel
• 50 spectra/pixel
• 3 ms/spectrum
d l ti
+ HAADF signal
• deconvolution
New possibilities for studying the lowenergy‐loss domain
Deconvolution techniques open the way to investigating nanophotonics with electrons
2.25 eV
U.V.I.R.
1.8 eV
1 15 eVIncrease in ΔE (f 0 35 V t 0 25 V) 1.15 eV
0 2 4 6Energy loss (eV)
(from 0.35 eV to 0.25 eV)
Cut‐off of zero loss signalat 0.9 eV (IR)
New technical possibilities (A. Gloter, A Douiri, M. Tencé)Highersignal‐to‐background ratio
Mapping surface plasmon resonances
of triangular silver nanoprisms
Bof triangular silver nanoprisms
78 nm edge long 78 nm edge long nanoprismnanoprism
A BC
D
Energy map of the “tip” modeJ. 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
0.81.03.4 eV
0.20.40.6
0.0• 100 Kv electrons• 78 nm long and 10 nm thick Ag prismg 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 V1.8eV 2.0eV 2.2eV 2.4eV
4 5 6
2 6 VEFTEM i 2.6eV 2.8eV 3.0eV 3.2eVEFTEM 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 electronsand photonsand 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 Sdetector (L. Zagonel+ S. Mazzucco + M. Kociak) Monochromatic electron
beam
Electron Induced Radiation Emission
(Cathodoluminescence)
Electron Energy-Loss
Absorption by EELS
gySpectrum
Emission by CL Absorption by EELSy2 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 apertureEELS 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 pendingL. 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?
CLEnergy 2.2 eV
EELS(radiative and non
CL (only radiative
modes)
radiative modes) No energy resolution limitation by the PSF detection system: optical 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 mostThe mostrecent
textbook on the market…
MRS Bulletin, january 2012on
“Spectroscopic Imaging in Electron Microscopy”
Ed S P k & C C lliEds. S. Pennycook & C. Colliex
Invited contributions :Invited contributions :
G. Botton, McMaster, CanadaM Varela et al ORNL USA and Madrid SpainM. Varela et al. ORNL, USA and Madrid, Spain
M. Kociak, Orsay, France & J. Garcia de Abajo, Madrid, SpainK. Suenaga et al. AIST, Japan
L J All t l M lb A t liL.J. Allen et al. Melbourne, AustraliaM. 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 OrsayThanks to all my colleagues at LPS Orsay
Guillaume Boudarham, Laura BocherN th li B Al d Gl tNathalie Brun, Alexandre Gloter,
Mathieu Kociak, Katia March, Stefano Mazzucco, Claudie Mory,
Odile Stéphan, Marcel Tencé, Almudena Torres-Pardo, Mike Walls,
Luis Zagonel and Alberto Zobellifrom LPS Orsay, France
Thanks to CNRS CNRS and to EC funded programs EUThanks 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