Scanning Transmission Electron

Microscopy

(STEM)

Henning Stahlberg

http://C-CINA.org

1Friday, March 19, 2010

sampleatom

eee

ee + e +

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einelastically scattered

primary electrons

small angles

X-rays

energy(light, etc.)

secondaryelectrons

Electron Sample Interaction

unscatteredprimary electrons

eelastically scatteredprimary electrons

wide angles

unscatteredprimary electrons

e

2Friday, March 19, 2010

thin sample

backscattered electronsE0 - E

secondary electronsE < 20 ... 50 eV

positive ions

Auger electronsE < 10 eV

X-ray radiation

visible light

inelastically scattered electronsE0 - E

elastically scattered electronsE0

Electron Sample Interaction

unscattered electronsE0

electron beamE0

3Friday, March 19, 2010

thin sample

Contrastelectron beam

objective lens

screen

unscatteredbeam

scatteredbeam

(phase shift = W)

Interference gives contrast

scattering angle

4Friday, March 19, 2010

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5Friday, March 19, 2010

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6Friday, March 19, 2010

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Saved with isotropic voxel size:

volume can be observed in all dimensions

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Olfactory bulb of zebrafish embryo:

15x15x15 µm: 500 cuts@30nm. 6nm per pixel

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7Friday, March 19, 2010

Olfactory bulb

of the mouse

20x20x20 µm

12 nm/pixel

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8Friday, March 19, 2010

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9Friday, March 19, 2010

The Transmission Electron Microscope

-200’000 Volt !

Sample

Viewing Screen

Vacuum !

10Friday, March 19, 2010

Transmission Electron Microscope

11Friday, March 19, 2010

Scanning Transmission Electron Microscope

Dark Field DetectorBright Field Detector

12Friday, March 19, 2010

STEM: VG HB-5 (Bioz U-160)

13Friday, March 19, 2010

O-$&"."*P):D-)

*C-.:)%N)'0*C1-

With Guy Cornelis, Biozentrum

Anti LCRV

STEM:

Mueller CA, Broz P, Müller SA, Ringler P, Erne-Brand F, Sorg I, Kuhn M, Engel A, Cornelis GR, Science. 2005 Oct 28;310(5748):674-6

14Friday, March 19, 2010

4B7!P)N$%,)!*&&):%)4D*'-

Mueller et al, J Mol Biol 99

15Friday, March 19, 2010

Z-contrast Image

Spectrometer

Annular Detector

Incident Probe

CCD-EELS Detector

Scanning Transmission Electron Microscopy

Z-Contrast Image – electrons scattered to high angles

Electron Energy Loss Spectrum – inelasticallyscattered electrons

A small probe is scanned

16Friday, March 19, 2010

viewing screen or CCD camera

specimen

electron source

probe!forming lens

defocus

Cowley, J. Elec Microsc Tech 3, 25 (1986)

u

v

Electron Ronchigram

17Friday, March 19, 2010

Disk of Least Confusion

Effect of Spherical Aberrations on the Ronchigram

18Friday, March 19, 2010

James and Browning, Ultramicroscopy 78, 125 (1999)

Effect of Spherical Aberrations on the Ronchigram

Disk of Least Confusion

19Friday, March 19, 2010

overfocused

underfocused

!f=0 nm Scherzer focus !f=-100 nm !f=-150 nm

!f=-200 nm !f=-300 nm !f=-350 nm

!f=100 nm !f=50 nm!f=150 nm

Ronchigrams from Si <110>

20Friday, March 19, 2010

Incident Probe

High-angle annular dark field (HAADF, 20...150 mrad), annular dark field (ADF, 10...20 mrad),

and bright field (BF, 0...10 mrad) detectors

STEM Imaging without an aberration corrector

21Friday, March 19, 2010

Electron Energy Loss Spectroscopy

Complements the Z-contrastImage

-Gives bonding and chemical Information

-The probe can be stopped anywhere in the image anda spectrum can be acquired

22Friday, March 19, 2010

EF

Evac

K

L

Sec

ondar

y E

lect

ron

AugerLight

X-Ray

INNER SHELL OUTER SHELL DE-EXCITATION

R. F. Egerton, EELS in the Electron Microscope, Plenum 1996

Electronic Excitations in the Microscope

23Friday, March 19, 2010

Main Regions of the EEL Spectrum

Direct Beam and LowLoss give thickness information

Core Losses give chemical and bonding information

24Friday, March 19, 2010

Applications

25Friday, March 19, 2010

Co Clusters in TiO2

A simple basic STEM experiment

26Friday, March 19, 2010

20 nm 5 nm

Regular Faceted Structure to the Dots Observed Outside the Layers

Y. Lei et al, Applied Physics Letters 82, 4262-4264 (2003)

Tin Quantum Dots in Si

27Friday, March 19, 2010

Direct Observation of Atomic Scale Defects

Twist Boundary in BSCCO Dislocation in YBCO

Grain Boundary In STO

28Friday, March 19, 2010

[0001] 2 nm0 1 2 3 4 5

Energy (keV)In

tensi

ty

Y/Al= !1.3 at%

Grain boundaryO Al

Y

O Al Grain interior

TEM/EDS Observation

HRTEM Image of the Y-doped GB Energy Dispersive Spectroscopy

- EDS reveals that Y is high confined to the GB plane

- However, the location of along the GB plane can not be determined

29Friday, March 19, 2010

STEM Image - Y-doped Boundary

-The basic grain boundary structure is relatively unaltered in comparison to the undoped case.

-The location of the Y ions are revealed by the STEM image

Y appears very bright in the Z-contrast image

30Friday, March 19, 2010

Energy Dispersive Elemental Mapping

31Friday, March 19, 2010

Unstained Bacteriophage T4Freeze-dried earthworm hemoglobin

Mass Measurement in Biological Specimens

The mass per unit length of a tail fiber is

866 +/- 76 kDa, indicating it is a trimer

32Friday, March 19, 2010

Resolution Approaching 1nm

STEM Tomography of Quantum Dots

Courtesy of I. Arslan

33Friday, March 19, 2010

Recent Advances

34Friday, March 19, 2010

Aberration Corrected STEM

CS Corrector

Pennycook, et al. AIP Conference Proceedings 683 (2003) 627

Before After

-Removes contrast reversals at critical spatial frequencies-Creates a more efficient probe

35Friday, March 19, 2010

Effect of the Cs Corrector

Batson, Dellby and Krivanek, Nature 418, 617 (2002)

Corrector Off Corrector On

Si (110)

Ronchigram

36Friday, March 19, 2010

0.78 Å

Information transfer to 0.607 Å

Image by Matt Chisholm,

Processing by Albina Borisevich and Andy Lupini

Aberration correction by Pete Nellist et al., Nion Co.

444

713 804

Improved Resolution and Contrast

37Friday, March 19, 2010

Cs-corrected STEM gives highest resolution.

STEM of SrTiO3

Atomic structure model for a 25° [001] symmetric tilt grain boundary in SrTiO3

McGibbon et al. Science 226 (1994) 102

Resolution < 1Å

Dislocation Cores

with Nigel BrowningBuban et al. J. of Electron Microscopy, in press

38Friday, March 19, 2010