The most versatile technique which involves analysis of the energy distribution of the in-elastically scattered electrons in the transmitted beam

1. 

2. ELECTRON ENERGY LOSS
SPECTROSCOPY
Presented to:
Dr. Athar Ibrahim
Presented by:
Khushbakhat Nida (MME-13-25)
Maria Iqbal (MME-13-26)
Nishat Riaz (MME-13-27)
IAM, BZU, MULTAN

3. HISTORY
 James Hillier
 RF Baker in the mid 1940s
 Research 1990s due to
 advance in microscope
 instrumentations and
 vacuum technology

4. INTRODUCTION
Electron energy loss spectroscopy (EELS) –The most
versatile technique which involves analysis of the energy
distribution of the in-elastically scattered electrons in
the transmitted beam
It is:
 high-sensitive
 non-destructive technique for the study of surface and
adsorbate vibrations
 low-energy electronic excitations

5. MAGNETIC SPECTROMETER
COMPONENTS:
 Source of electrons
 Condenser lenses
 Specimen
 ADF detector
 Display screen
 EELS Spectrometer

6.  Discriminates the energy loss electrons on the basis of
their absolute energy.
 The signal from the electron energy loss spectrometer
can be used to generate an EELS spectrum
 The spectrometer can be used to produce a
compositional map

7. EELS spectrum
It has Three regions :
-Each region arises due to a different
group of electron/sample interactions.
 Region 1 (0 to 10 eV) is the
zero-loss region.
 Region 2 (10 to 60 eV) is
the low-loss region.
 Region 3 (>60 eV),
the core-loss region

8. Zero-Loss Peak
 It is the main feature in EELS spectra of thin specimens.
 Originates from electrons that have lost NO energy
 Width of the zero-loss peak is energy
spread of the electron source
 Less analytical information
about the sample
 Used to calibrate the Energy scale
 Phonons are lattice vibrations, which
are equal to heating the specimen.
 This effect may lead to a damage of the sample

9. Low-Loss area
 It reflects excitation of plasmons and interband
transitions.
 Plasmons are longitudinal oscillations of free
electrons, which decay either in photons or phonons.
 It is caused by weakly bonded.
 It depends on local density of the weakly bonded
electrons.
 The typical lifetime of plasmons is about 10-15 s.

10.  Interband transition: the
transition between the
conduction and valence bands
(electrons and holes)
 Intraband transitions: the
transitions between the
quantized levels within the
conduction or valence band. It
known also as the itersubband
transition.

11. High-loss Region
 The most important region of the
EELS spectrum for microanalysis
 The signal in the core-loss region
is very weak relative to that in the
zero-loss and low-loss regions.
Therefore, the core-loss region of
the spectrum is often amplified 50
to 100 times

12.  The peaks or edges, arise because of interactions
between the incident electrons and the inner-shell
electrons of atoms in the specimen
 When an incident electron ionizes an atom, it
produced a specific amount of energy. The amount of
energy lost in ionizing the target atoms is the electron
energy loss

13. ADVANTAGES
DISADVANTAGES
 Higher core-loss signal
 Higher ultimate spatial resolution
 Absolute, standard less quantification
 Structural information available
 Higher spectral background
 Very thin specimen needed
 Possible inaccuracy in crystals
 More operator intensive

14. APPLICATIONS:
 Thickness measurements
 Pressure measurements
 Analytical electron microscopy (AEM)