Carl Zeiss Microscopy GmbH

Carl Zeiss Microscopy GmbH 

- a merger of NTS and MicroImaging 

Gerd Benner 

Principal 

18.06.2012

New analytical capabilities of an incolumn 

EFTEM with monochromator 

Gerd Benner 

Carl Zeiss Microscopy GmbH, Carl-Zeiss-Straße 22, 73447 Oberkochen, Germany 

Philipp Wachsmuth, Ralf Hambach and Ute Kaiser 

Group of EM of Material Science, Ulm University, Albert-Einstein-Allee 11, 89081 

Ulm, Germany 

Martin Pfannmoeller and Rasmus Schroder 

CellNetworks, BioQuant, Heidelberg University, 69120 Heidelberg, Germany 

EELS WS Uppsala_June 2012 

Company confidental 2

Outline 

1 

2 

3 

4 

5 

The Libra 200 MC 

Monochromator: Design and Features 

In-column Energy Filter: Design and Features 

Advantage of low beam voltages for spectroscopy 

New analytical capabilities 

EELS WS Uppsala_June 2012 Company confidental 

3

L200: High performance analytical EFTEM 


• FEG with Schottky field emitter 

High Brightness, low energy spread (

LIBRA ® 200 MC C S TEM 

FEG 

+ Monochromator 

Condenser 

(C1, C2 & C3) 

Objective 

C S Corrector 

Projector 1 

(P1, P2 & P3) 

Corrected 

Omega Filter 

Projector 2 

(P4, P5 & P6) 

Viewing chamber 

+ Detectors 


0 

OL 

D1 

Hx1 

D2 

Hx2 

Company confidental 

dispersive 

plane (slit) 

Entrance Image 

Plane 

Achromatic 

Image Plane 

Dispersive 

(EELS) plane 

5

Elemental EDS SrTiO 3 

C S probe corrected L200 Havard (David Bell) 

Gatan Drift correction 

and spatial image processing with 

Simultanious Multivariate Analysis 

software from Musashe Wantable 

Dual detector (2 x 0.2sr) EDS 

acquisition, collected over 1 hr. 

Each EDS map on the right is a sum of 

matching EDS maps from 2 individual 

detectors and 

Doing correlated spectrum imaging NOT 

possible on only one detector system. 


Sr (M-K) 

Ti L O K 


Correlated Elemental EELS map of SrTiO 3 

C S probe corrected L200 Havard (David Bell) 


Sr Ti O 

Simultaneous EELS map shows slightly better signal to noise 

than EDX map as expected. 


Outline 

1 

2 

3 

4 

5 







8

Design of the Monochromator 

� Electrostatic Omega-type MC 

without stigmatic Cross Over 

� Gun lens aperture 

for beam current limitation 

� High Dispersion 

(12 µm/eV @ 4 kV U ext) 

� Piezo driven multi slit array 

� Straight beam path (MC off) 

� Dispersion free; virtual, round CO image 



Dispersive 

Plane (Slit) 

9

1,20 

ratio 

1.0 1,00 

0,80 0.8 

0,60 0.6 

Ratio 

0.4 0,40 

0,20 0.2 

Features of the Monochromator 

0.2eV 

0.14eV 

peak 


0.68eV 

0.24eV 

Current 

0,00 

0,1 0,15 0,2 0,25 

Energy width (FWHM) 

0,3 0,35 0,4 

0.4 

0.1 0.2 0.3 0.4 

energy width (FWHM) / eV 

Ref: Peak ratio Tenn: Peak ratio Ref: Filter Factor Tenn: Filter Factor 

�� FWHM @ 200kV 

Deep drop of ZL peak 

�� FWGM @ 40kV 

(Exp. Time 1.2s 

MC slit 0.5µm) 

L200 

MC 

VG 

VG 

44meV* 

* D.C. Bell, et al., Ultramicroscopy (2012), 

doi:10.1016/j.ultramic.2011.12.001 


Highly Resolved Low Loss Spectroscopy (VEELS) 


ROI 

1 st plasmon 

2 nd plasmon 


20 kV 

Seite 

11

Monochromated HAADF STEM 

Uncorrected Beam Profile 


I @ 0,7eV 

I @ 0.2eV 

4x scalled 

0.28nm 

0.25nm 

-0.5 0 0,5 

Si 

raw data 

�E = 250 meV 

Si 

Fourier filtering 

�E = 93 meV 

FFT shows 422 reflexes 

b 

FWHM of ZL peak with = 93 meV 


Highly resolved core loss spectroscopy 

A B 


C S STEM 

d = 0.2 - 1nm 

Exp. time: 4s 

Pre-peaks A and B and shape indicates 

electronic structure of anatase 

Electronic structure of 

titania aerogels from soft 

x-ray absorption 

spectroscopy, 

Cheynet et al.,Ultramicroscopy,110 (2010) 


Improved Resolution & Contrast enhancement at low kV 

FFT FFT 

Without Monochromator With Monochromator 

Double wall carbon nanotubes at 80 kV 


Sample courtesy of X. Devaux, Ecole de Mines, Nancy, France 


14

Outline 

1 

2 

3 

4 

5 







15

Imaging Energy Filter 

conjugate 


conjugate 

Entrance Pupil Plane 

Entrance Image Plane 

Achromatic Image Plane 

Image points focusing 

Dispersive Plane 

Slit 

Energy focusing 


Corrected Omega Performance 

Excellent energy resol. 

Drift [eV/min] 

0,250 

0,200 

0,150 

0,100 

0,050 

0,000 


44meV* 

0,5 um 

MC-Spalt 

(0.05eV) 

at 40kV 

CBED Si 100 

Spectrum drift 

Low spectrum drift rate 

Drift 

Mean (0,036 eV/min) 

Specification 

1 2 3 4 5 6 7 8 9 10 

Time [min] 

120-144 meV 

96-120 meV 

72-96 meV 

48-72 meV 

24-48 meV 

0-24 meV 

Large acceptance angle 

8 eV 

High Isochromaticity 

Company confidental 17 

2k

Application: Zero Loss (ZL) Energy Filtering 

Exampel: Precession Electron Diffraction (PED) of Mayenite 


unfiltered ZL - filtered 

FOLZ 

PED angle 0.3º 

� 

P 

PED angle 3º 


�

Application: Electron Spectroscopic Imaging 

Example: Analysis of failing vias 

100 nm O map 

100 nm N map 100 nm 

Ti map 


CBED Si 100 

ESI Maps 

20eV 

Plasmon Image 

BF 

15eV 


Application: Plasmon Loss Imaging 

Surface and volume plasmon of Nanoparticel 

58 eV 4 eV 

Nanoparticle Sample 


Volume Plasmons 

Surface Plasmons 


Seite 

20

Application: Electron Energy Loss Spectroscopy (EELS) 

Example: Different materials 

Co Nanoparticle 

EEL spectrum of the Co L 2,3 

with a FWHM of �E = 0,7eV (blue) and �E = 

0,2eV (red). For better comparability the 

latter one has be scaled by a factor 2.5 


Co L 2,3 edge 

Mn xO y 

ELNES for the idendification of 

ocidations states 

y 

y 

SrTiO 3/Cr Interface: 

E 

E 

Lateral resolved EELS across 

interfaces and multilayer systems 


Application: Energy–loss Magnetic Chiral Dichroism (EMCD) 

Example: Cobalt ferrite nano crystal 


Fe L 2,3 

EMCD 

10 µm Kondensorblende 

200 nm 

STEM DF image 

EMCD signal of a cobalt 

ferrite nano crystal I. Ennen, TU Wien, Austria 

A. Hütten, Bielefeld University, Germany 

0 

A 

B 

g 


Seite 

22

Outline 

1 

2 

3 

4 

5 







23

SALVE II Microscope 

@ Carl Zeiss 


Imaging of beam sensitive materials 

with atomic resolution at low voltages (20kV-80kV) 


24

Atomic resolution @ 20kV with Cs-Corretion & MC (0.15eV) 

�E 0.15eV 

India customer visit_ Jan. 2012 

FFT 

Si(110) 

�E 0.7eV w/o MC 

272 

pm 

Si(110) 

Seite 

25

Advantages of LV – Spectroscopy: 

High Dispersion 

Beam 

Voltage /kV 


Dispersion 

µm/eV 

200 

(SESAM) 

6.4 

200 

(LIBRA) 

1.84 

80 4.26 

40 8.25 

20 16.2 

Intensity [a.u.] 

1.1 

1.0 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0.0 

-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 

Energy [eV] 

�� FWHM @ 20kV 

(Exp. Time 1sec) 

0.5um slit, FWHM 0.054 eV 

2.0um slit, FWHM 0.095 eV 



High Isochromatic Image 

CMOS F416 (4k x4k pixel, 15.6µm) 

TVIPS GmbH, 


~ 0.13 eV 



Higher inelastic cross section (for core loss EELS) 


Jump ratio ~4.2 

Jump ratio ~3.6 

pi* 

sigma* 

High signal to noise, high jump ratio, high EELS resolution 

Graphene 20kV(ZEISS) 

Graphene 80kV(TITAN) 

Amorphous C 80kV(TITAN) 


Seite 

28


No Cerenkov radiation allows VEELS close to ZL 


200kV, 200nm 

Cerencov 

20kV, 20nm 

VEELS Spectrum of Ge (20kV) 

Row spectrum 

U. Kaiser et al., Ultramicroscopy,111 (2011), 1239 -1246 

Energy loss function 

Refractive index 


Seite 

29


Delocalization in Low Loss Spectroscopy 

Delocalization at �E = 16,5 eV 

(theoretrical and experimental) 

M. Stöger-Pollach, Micron 41 (2010), pp. 577-584 


Delocalization as a function of the energy 

loss for different voltages 


Advantages of Low Voltage Spectroscopy 

Summary 

• High dispersion of spectrometer (16,4eV @20kV) 

� Point spread function of SSCCD less critical => better energy resolution =>better 

access to band gaps in the very low loss 

� Improved Non-Isochromaticity and Transmissivity 

• Less beam damage (depending on damage mechanism) 

• Higher inelastic cross section => better signal/noise (= nanoparticles!) 

• No Cerenkov radiation 

� Excitation of relativistic energy losses in the band gap of semiconductors and insulators as 

soon as v e>c 0/n 

• Less delocalization at Low Energy Losses (classical picture) 

� Reduced Coulomb interaction between the probe electron and the sample. 

But: 

Sample preparation more critical for bulk samples, since thinn samples are needed. 



Outline 

1 

2 

3 

4 

5 







32

Organic solar cells: 

Low Loos Spectroscopy_TEM Kolloquium_GBn_July 2010 

Lateral distribution of Polymers 

Challenge: 

Polymers only distinguish in 

electronic structure 

� not visible in normal TEM 

images 

Solution: 

Phase contrast microscopy 

Low Loss spectroscopy 

33

VEELS Spectrum of polymers for an organic solar cell 

0 eV 

15 eV 

Pol. 1 


Pol. 2 

Pol. 1+2 

Pol. 2 

Pol. 1 

1 5 10 15 

Energy Loss [eV] 


34

Segmentation of a polymer:fullerene blend 


Spectrum Image 3 -10eV 

nonlinear statistical 

methods => 

Principal components 

Pfannmöller et al., Nano Lett. 11 (2011), 3099–3107 


HJ 

P3HT 

PCBM

Principal of �-q Maps 

conjugate 

Electron Energy Loss 

Spectrum 


� EPA < �E FWHM x D 

(Strongly) demagnified SA Image 

limited by illumination aperture 

Slit aperture 

Diffraction Pattern 

Energy Filter 

eV 

Graphite 


qx

�-q map in low loss range and carbon K-edge 

Spectrum elongation 

can be streched 


Resolution 

Energy: 0.2eV 

Momentum: 0.1-0.2Å -1 

P. Wachsmuth, R. Hambach, U. Kaiser 

Ulm University, Ulm, Germany 


Seite 

37


38

Carl Zeiss Microscopy GmbH

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?