1. Analytical Transmissions Electron Microscopy (TEM)
Part I:
The microscope
Sample preparation
Imaging
Part II:
Diffraction
Defects
Part III
Spectroscopy
MENA 3100: Diff

2. Repetision: Electron Diffraction: Powder X-ray diffraction:
Small wave length
Large Ewald sphere
-- Perfect crystals plane
Very sensitive to changes in the crystal
structure
Small diffraction
Strong intensity – short exposure time
Directly observed on the viewing
screen
Obtained from very small crystals 
Larger wave length
Small Ewald sphere
Ring pattern
Larger driffrationangle
Lower intensity
Easier to interpret

3. Electron matter interactions
Coherent incident
high-kV beam
Second electrons
From within the specimen (SEM)
sample
Incoherent elastic
backscattered electrons (SEM)
Characteristic
X-rays (EDS)
Auger electrons (XPS)
Visible light
Sample
Incoherent inelastic
scattered electrons
(EELS)
Bremsstrahlung
X-rays (EDS)
Direct beam
(imaging, diffraction,
EELS)
Incoherent elastic
forward scattered
Electrons (STEM,
diffraction,EELS)
Coherent elastic
scattered electrons (STEM,
Diffraction, EELS)

4. The characteristic energy transitions
Observable with EELS and EDS
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

5. Empty states
Valence electrons
M shell
L shell
K shell
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

6. 1s 2s 2p 3s 3p 3d
Empty states
K shell
L shell
M shell K L1
L2,3
Kα1
Lα1
EELS
Kβ1
EDS
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

7. Energy dispersive X-ray spectroscopyM L Lα kα K kβ hν
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

8. EELS Eo Eo K-edge (Si) – 1s orbital M L K L-edge (Si)
– 2s and 2p orbital
Filled bands
Conduction band
Eb(L)=Eo-Eb(cond.band-L)
Eb(K)=Eo-E(cond.band-K)

9. Energy Dispersive X-ray Spectroscopy
(EDS)
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

10. EDS spectrum
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

11. X-ray Spectroscopy EDS: Energy Dispersive Spectroscopy
EDXS: Energy Dispersive X-ray Spectroscopy
X-EDS: X-ray Energy Dispersive Spectroscopy
EDX: Energy Dispersive X-ray analysis
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

12. Quantification 𝐶 𝐴 𝐶 𝐵 = 𝐾 𝐴𝐵 𝐼 𝐴 𝐼 𝐵
Peak intensities are proportional to concentration and specimen thickness.
They removed the effects of variable specimen thickness by taking ratios of intensities for elemental peaks and introduced a “k-factor” to relate the intensity ratio to concentration ratio:
𝐶 𝐴 𝐶 𝐵 = 𝐾 𝐴𝐵 𝐼 𝐴 𝐼 𝐵
Each pair of elements requires a different k-factor, which depends on detector efficiency, ionization cross-section and fluorescence yield of the two elements concerned.
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

13. The Detector MENA 3100: Spectroscopy MENA 3100: Spectroscopy
Crystal (Si(Li)): Absorbs the energy of incoming x-rays by ionization, yielding free electrons in the crystal that become conductive and produce an electrical charge bias. The x-ray absorption thus converts the energy of individual x-rays into electrical voltages of proportional size; the electrical pulses correspond to the characteristic x-rays of the element.
In older detector designs, the collection electrode is centrally located with an external FET (field effect transistor) to convert the current into a voltage and thus represents the first stage of amplification. Newer designs integrate the FET directly into the chip, which greatly improves energy resolution and throughput. This is due to the reduction of capacitance between anode and FET, which reduces electronic noise.
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

14. Detection Mechanism MENA 3100: Spectroscopy MENA 3100: Spectroscopy
When X-rays deposit energy in a semiconductor, electrons are transferred from the valence band to the conduction band, creating electron-hole pairs, as we saw back in Section 4.4. The energy required for this transfer in Si is 3.8 eV at liquid-N2 temperature. (This energy is a statistical quantity, so don’t try to link it directly to the band gap.) Since characteristic X-rays typically have energies well above 1 keV, thousands of electron-hole pairs can be generated by a single X-ray. The number of electrons or holes created is directly proportional to the energy of the X-ray photon. Even though all the X-ray energy is not, in fact, converted to electron-hole pairs, enough are created for us to collect sufficient signal to distinguish most elements in the periodic table, with good statistical precision.
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

15. MENA 3100: Spectroscopy MENA 3100: Spectroscopy
The silicon drift detector (SDD) is fabricated from high-purity silicon with a large area contact on the entrance side. On the opposite side is a central small anode contact, which is surrounded by a number of concentric drift electrodes. When a bias is applied to the SDD detector chip and the detector is exposed to X-rays, it converts each X-ray detected to an electron cloud with a charge that is proportional to the characteristic energy of that X-ray. These electrons are then “drifted” down a field gradient applied between the drift rings and are collected at the anode
Oxford
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

16. EDS SEM TEM MENA 3100: Spectroscopy MENA 3100: Spectroscopy
The weight percents of each element CA and CB can then be related to IA and IB thus K is the cliff-lorimer factor
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

17. EDS mapping
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

18. Recent advances MENA 3100: Spectroscopy MENA 3100: Spectroscopy
SDD: consisting of concentric rings of p-doped Si implanted on a single crystal of n-Si across which a high voltage is applied to pick up the electrons generated as X-rays enter the side opposite the p-doped rings (Figure 32.8A–C). Applying a voltage from inside to outside the detector (rather than front to back as in a Si(Li)) permits collection of the electrons generated in the n-Si with a 4 lower voltage. Because the central anode in the middle of the p-doped rings has a much smaller capacitance than the large anode at the rear face of a Si(Li) detector (Figure 32.3A–C), a very high throughput of counts is possible, peaking at output rates of many hundred of kcps.
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

19. Comparison Low Z element
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

20. Comparison on resolution
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

21. Artefacts in EDS Si escape peak:
A small fraction of the energy is lost and not transformed into
electronhole pairs
2. Sum peak:
Two photons will enter the detector at exactly the same time. The analyzer then registers an energy corresponding to the sum of the two photons.
Likely to occur if:
- The input count rate is high.
- The dead times are > 60%.
- There are major characteristic peaks in the spectrum.
Because the detector is not a perfect sink for all the X-ray energy, it is possible that a small fraction of the energy is lost and not transformed into electronhole pairs. The easiest way for this to happen is if the incoming photon of energy E fluoresces a Si Ka X-ray (energy 1.74 keV) which escapes from the intrinsic region of the detector. The detector then registers an apparent X-ray energy of (E – 1.74) keV
The sum peak arises when the count rate exceeds the electronics’ ability to discriminate all the individual pulses and so-called ‘pulse pile-up’ occurs.
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

22. Thickness variations due to milling Contaminants and reaction products
3. Fluorescence:
This is a characteristic peak from the Si (or Ge) in the detector dead layer.
Sample preparation artefacts (ion milling , grids, reaction to solvent)
Cu/Ni slot
Thickness variations due to milling
Contaminants and reaction products
This is a characteristic peak from the Si (or Ge) in the detector dead layer. Incoming photons can fluoresce atoms in the dead layer and the resulting Si Ka or Ge K/L X-rays enter the
intrinsic region of the detector which cannot distinguish their source and, therefore, register a small peak in the spectrum. As semiconductor detector design has improved and dead layers have decreased in thickness, the internal fluorescence peak artifact has shrunk but it has not yet disappeared entirely. So beware
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

23. Electron Energy Loss Spectroscopy
(EELS)
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

24. Omega filter MENA 3100: Spectroscopy MENA 3100: Spectroscopy
The filter is placed in the TEM column between the intermediate and projector lenses and consists of a set of magnetic prisms arranged in an O shape which disperses the electrons off axis,
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

25. Gatan Imaging Filter (GIF)
Post column energy filter
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

26. Microscope outline Electron gun Condenser aperture Sample holder
Objective aperture
Objective lens
Intermediate aperture
Diffraction lens
Projector lenses
Intermediate lens
Fluorescent screen
Gatan Imaging Filter
For EELS

27. MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

28. Projector crossover
Viewing screen
Slit
90o magnetic
prism
Detector
Multipole lenses
Beam trap aperture

29. Energy Losses Zero Loss (includes quasi-elastic scattering)
Intra-/Inter-band transitions (band gap)
Cherenkov losses
Bremsstrahlung
Plasmon losses
Core losses
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

30. EEL Spectral background
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

31. Low-Loss EELS
Core-Loss EELS

32. Low-Loss EELS

33. Single electron outer shell
excitation
Zero Loss Peak
Elastic scattering:
Coulomb attraction by nucleus
Inelastic scattering:
Coulomb repulsion (outer shell electrons)

34. The Zero Loss Peak (ZLP)
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

35. Low-Loss EELS: Bulk plasmons
Outer-shell inelastic scattering involving many atoms of the solid.
Collective effect is known as a plasma resonance
An oscillation of the valence electron density
𝐸 𝑝 = ℎ 2𝜋 𝑁 𝑒 2 𝑚 𝑒 𝜀 0
h: Planck constant
N: n/V : Valence electron density
e: Elementary charge
me: Electron mass
εO: Permittivity of free space
Plasmon peak

36. Low-Loss EELS: Surface plasmons
Surface plasmon (Es):
Vacuum/metal interface:
Dielectric/metal boundary:
Interface between two metals:
𝐸 𝑠 = 𝐸 𝑝 2
ZLP
𝐸 𝑠 = 𝐸 𝑝 1−ε
𝐸 𝑠 = 𝐸 𝑎 2 + 𝐸 𝑏 2 2
A. Thøgersen,et al.  Journal of Applied Physics 109, (2011). 

37. Low-Loss EELS: Energy filtering
Kundmann M., Introduction to EELS in TEM, EELS course 2005 San Francisco

38. Low-Loss EELS: Energy filtering
Kundmann M., Introduction to EELS in TEM, EELS course 2005 San Francisco

39. EFTEM imaging of Si/aSi/ITO (Indium Tin Oxide) stack sample for REC
Low-Loss EELS: Energy filtering
EFTEM imaging of Si/aSi/ITO (Indium Tin Oxide) stack sample for REC
TEM image Si
ITO

40. EFTEM imaging of Si/aSi/ITO (Indium Tin Oxide) stack sample for REC
Low-Loss EELS: Energy filtering
EFTEM imaging of Si/aSi/ITO (Indium Tin Oxide) stack sample for REC
EFTEM (16 eV) EFTEM (23 eV)
TEM image

41. 𝑡= λ 𝑝 𝐼 𝑝 𝐼 𝑜 Low-Loss EELS: Thickness t = thickness
𝑡= λ 𝑝 𝐼 𝑝 𝐼 𝑜
t = thickness
λp = plasmon mean free path
Ip = Intensity of the plasmon peak
Io = Intensity of the zero loss peak

42. Core-Loss EELS (Energy-Loss Near-Edge Structure)

43. Eo Eo
K-edge (Si) – 1s orbital M L K
L-edge (Si)
– 2s and 2p orbital
Filled bands
Conduction band
Eb(L)=Eo-Eb(cond.band-L)
Eb(K)=Eo-E(cond.band-K)

44. Core-Loss EELS: Peak shape
Shape of the edge is a signature of the transition:
K-edges: 1s states -- typical sawtooth profile
L2,3-edges -- have a delayed maximum but can contain intense narrow peaks at the onset, known as “white lines”, corresponding to transitions to narrow d bands.

45. MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

46. Microanalysis
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

47. EFTEM:
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

48. MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

49. Spectral Imaging (SI) STEM-SI EFTEM-SI MENA 3100: Spectroscopy
B.Chaffer et al. Analytical and Bioanalytical Chemistry
(2008) 390, Issue 6, pp
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

50. Spectral Imaging (SI) STEM-SI EFTEM-SI MENA 3100: Spectroscopy

51. MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

52. MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

53. EDS vs. EELS
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy

54. Applications
MENA 3100: Spectroscopy
MENA 3100: Spectroscopy