Microscopical Characterisation of
Solid and Biological Materials
KOO 065
(“Microanalysis Course” or “Unknown samples”)
Lecture 1
Crispin Hetherington
roll call and introduction to course
Electron scattering,
TEM instrument,
image contrast,
EELS
nCHREM, Lund University
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”pre-knowledge”
“Materials Analysis at the Nanoscale” KOO 105
Kimberly Dick Thelander and Anders Mikkelsen
Overview of solid state microanalysis methods; The electron microscope as an
analytical tool; Identification of phases by morphology, chemical composition,
electron diffraction and high resolution transmission electron microscopy;
Scanning electron microscopy; XEDS and EELS for element analysis; Scanning
probe microscopy; LEED; Synchrotron based analysis; X-ray photoelectron
spectroscopy
That course structure was lectures, and book study
(Williams & Carter) and a few lab classes
nCHREM, Lund University
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This course
“Microscopical Characterisation of Solid and
Biological Materials” KOO 065
Reine Wallenberg
This course structure is lab classes
(JSM-6700F , JEM-3000F),
unknown sample investigation
And to help you understand the lab classes, there
is book study (Williams & Carter) and a few
lectures
nCHREM, Lund University
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Lecture 1 - TEM
• 
• 
• 
• 
• 
Electrons,
TEM instrument,
Image contrast,
STEM
EELS
nCHREM, Lund University
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Hur stor är
en nm?
SEM
Verktyg:
SPM
TEM
- ögat
- Svepelektronmikroskop
- Svepprobsmikroskop
- Transmissionselektronmikroskop
The National Center for HREM, Lund University, Reine
Wallenberg
Why do we use electrons?
•  charged particles interact
strongly with the sample
•  charged particles so we
can use magnetic lenses
•  short wavelength
(0.002nm) allows imaging
at high resolution
do = 0.66 Cs1/4λ3/4
sem
sem
sem te
sem
tem
stem
nCHREM, Lund University
stem
7
Transmission Electron Microscope
electron gun
accelerator
condenser lens condenser aperture
beam deflectors
Xray spectrometer
specimen holder
objective lens
objective aperture
water cooling
intermediate aperture
projector lens
camera
EELS spectrometer
lead shielding
How do we generate electron beam?
•  thermal emission (W or LaB6 crystal) or
field emission
W
•  Accelerate the electrons by 60-300kV
–  electrons behave like waves
–  high kV for resolution
–  low kV to minimise beam damage
•  ~1eV energy spread
–  required for imaging and spectroscopy
How to control the illumination
wide parallel beam
or small probe
Beam Shift
- also used to scan the beam in STEM
Beam Tilt
- to put the beam onto the optic axis
How big is a TEM specimen?
•  3mm across
•  thin all over (0.1mm)
•  important bit must be
electron transparent
(10-100nm)
•  Specimen holders are
important and fragile
The heart of the microscope: the objective lens
•  Quality of this lens determines image
resolution
resolution limit do = 0.66Cs1/4λ3/4
–  must be a ”round lens” which means
astigmatism must be corrected
•  Lens strength usually held in narrow
range
–  change sample height for coarse focusing
–  change lens current BY SMALL
AMOUNTS for fine focusing
Schematic diagram of the objective lens area
showing the positions of the objective- and selected
area apertures
thin ”electron transparent” sample
In TEM, we illuminate the
sample uniformly and we
use thin samples that
transmit the fast electrons.
The lens focusses all the
scattered and unscattered
electrons onto the camera...
Err!?
sample
lens
camera
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electron
beam
(aperture in diffraction plane
& energy filter)
(aperture in diffraction plane)
(contrast transfer function
in diffraction plane)
image
specimen
Overview of Image Contrast
Mass/thickness
“absorption”
Diffraction contrast
phase contrast
15
Mass-thickness contrast
•  The objective aperture
is placed around the
forward-scattered beam,
excluding many of the
scattered electrons.
Diffraction Contrast
need to think about Bragg s Law
2dhklsinθ = nλ
dhkl is crystal lattice spacing
n denotes fractional lattice spacings
θ  is Bragg angle
θ
θ
•  The objective aperture
is placed around the
forward-scattered beam
•  or the diffracted beam.
17
phase object
incident plane wave
atoms
q(x) = exp{-iσϕ(x)}
σ = interaction constant ϕ = projected potential
transmitted wave
note: phase of wavefront has
changed - but amplitude unaffected
18
TEM mode
STEM mode
condenser lens
objective lens
TEM and STEM - beam alignment, lens astigmatism, focus...
STEM with analytical
electron microscopy (AEM)
HAADF, High angle annular
dark field detector
GIF – Gatan Imaging Filter,
for electron energy loss
spectrometer and energy
filtered TEM
The National Center for HREM, Lund University,
Elastic scattering
• The electrons do not lose
energy
Rutherford
Backscatter
(SEM)
• At a distance it looks like
elastic collision
e-
• Wave description also works –
phase change only
• Electrons passing close to
nucleus – stronger scattering
• Electrons are scattered by the
potential (Coulomb interaction)
as opposed to x-rays (electron
density)
High-angle
Scattered
(HAADF)
Forward
scattered
<10 mrad Unscattered
(HREM)
(HREM)
Inelastic scattering
The chemists
microscope!
Incoming electrons ionize
the atom (core-shell
excitation), loses energy
collect emitted x-rays
(XEDS)
Or - the energy loss can
be measured (EELS),
typically up to 3kV loss.
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(P)EELS Parallel Electron Energy Loss spectrometer
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EELS Summary (NiO spectrum) 24
Gatan Image Filter
5 cm 5 cm Magne*c sector disperses electrons according to energy. Can re-­‐create image, using selected energy electrons only Al
Ti
3 images each around:
O K edge: @ 532 eV
Ti L23 edge: @ 455 eV
Al K edge: @ 1560 eV
O
Colour overlays, - RGB
- assign a colour to each
elemental map:
O
Ti
Al
- superimpose three layers
to form RGB composite