overview of types of electron microscopy

1. Types of Electron
Microscope
1Nancy Bansal

2. Types of Electron Microscope
• Transmission Electron Microscope
• Scanning Electron Microscope
2Nancy Bansal

3. Transmission Electron Microscope
• The Original Form of EM that uses the high
voltage Beam of Electrons to create an image.
• Its has Resolution power up to 0.5 Å.
• Most Powerful for observing
minute objects
3Nancy Bansal

4. Components
4Nancy Bansal

5. Mechanism
• Electron Gun Produces Beam of 100KeV.
• Anode and Cathode accelerate Beam.
• Focusing occur by Electrostatic and
electromagnetic lenses
• Beam strikes the sample and pass through it.
• After emerging out it carries information about
Sample and magnify it by objective lens
• Information can be analyzed by Screen or Film or
CCD Cameras on LCD or monitor.
5Nancy Bansal

6. Advantages
• TEMs offer the most powerful magnification,
potentially over one million times or more
• TEMs provide information on element and
compound structure
• Images are high-quality and detailed
• TEMs are able to yield information of surface
features, shape, size and structure
• They are easy to operate with proper training
6Nancy Bansal

7. Scanning Electron Microscope
• SEM produces the image by scanning it with
focus beam of electron.
• Electrons interact with electrons in sample
and convey information in form of signals to
detectors. E.g. topography & sample surface.
• SEM can achieve resolution better than 1
nanometer
• Raster image focusing is used
7Nancy Bansal

8. Mechanism
• When High energy Electrons strikes the
surface, it lose energy by diff. mechanisms like
heat, emission of low energy secondary
electrons and high energy backscattered
electrons.
• X-ray or light emerges from sample that
carries information on it.
8Nancy Bansal

9. Advantages
• Its basically used for biological samples
• It can scan the processes occurring on surface
and tells about topography and composition.
• Enable us to view without thinning
dehydrating fixing the sample
• Can scan bulk samples upto 2-3 cm which can
not be examined by TEM.
• View obtained is in 3D.
• ESEM produce image of Wet, gas & Vacuumed
Samples and biological samples. 9Nancy Bansal

10. Differences
TEM
• Based on transmitted
electrons
• Electrons are directly pointed
toward the sample and the
parts through which electrons
are passed are illuminated in
the image.
• TEM seeks to see what is
inside or beyond the surface
• TEM shows the sample as a
whole.
SEM
• Based on scattered electrons
• The scattered electrons
produced the image of the
sample after the microscope
collects and counts the
scattered electrons.
• SEM focuses on the sample’s
surface and its composition
• SEM also shows the sample bit
by bit
10Nancy Bansal

11. TEM
• TEM delivers a two-
dimensional picture.
• TEM has up to a 50 million
magnification level.
• The resolution of TEM is 0.5
Å.
• TEM requires the sample to
be prepared in a TEM grid and
placed in the middle of the
specialized chamber of the
microscope. The image is
produced by the microscope
via fluorescent screens.
SEM
• SEM also provides a three-
dimensional image
• SEM only offers 2 million as a
maximum level of
magnification.
• SEM has resolution of about
0.4 nm.
• In SEM, the sample is prepared
on specialized aluminum stubs
and placed on the bottom of
the chamber of the
instrument. The image of the
sample is projected onto the
CRT or television-like screen.
11Nancy Bansal

12. Thank you
12Nancy Bansal