The document summarizes the scanning electron microscope (SEM). It describes that the SEM uses a low-energy electron beam to scan microorganisms, providing higher resolution images than light microscopes. The SEM works by using kinetic energy to generate signals from secondary and backscattered electrons emitted from the specimen when interacted with by the electron beam. These signals are used to create three-dimensional images showing the specimen's topography, morphology, composition, and crystallographic structure. Applications of the SEM include industrial quality control, nanoscience, biomedical studies, microbiology, and cosmetic analysis.

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Seminar on
Scanning
Electron
Microscope
(SEM)
Kongu Engineering College
By: Kavin Kumar S
[23MER015]
Hariprathap G K K
[23MER011]
Date:05.01.2024

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Introduction
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• The first Scanning Electron Microscope was
initially made by Mafred von Ardenne in 1937
with an aim to surpass the transmission
electron Microscope.
• He also aimed at reducing the problems of
chromatic aberrations images produced by the
Transmission electron Microscopes.
• SEM provides high-resolution , three-
dimensional image.

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The Scanning Electron Microscope (SEM)
uses a low-energy electron beam to scan
microorganisms. It was developed due to the
limited resolution of light microscopes, as
electron microscopes have shorter
wavelengths, enabling better resolution.
Scanning Electron Microscope (SEM)

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Principle of Scanning Electron
Microscope (SEM)
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The Scanning Electron Microscope (SEM)
uses kinetic energy to generate signals from
secondary and backscattered electrons. These
electrons, emitted from the specimen, help
create images. Secondary electrons reveal the
specimen's morphology and topography, while
backscattered electrons highlight elemental
composition contrasts.

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Parts of a Scanning Electron
Microscope (SEM)
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• Electron Source
• Lenses
• Scanning Coil
• Detector
• CRT(Cathode Ray Tube) - A special
vacuum tube that creates an image
• Power supply
• Vacuum system

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SEM yields the information about the
specimen:
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(i) Topography : The surface features of an object
and its texture
(ii)Morphology : The shape, size and arrangement
of particles making up the object on the surface
of the sample
(iii)Composition : The constituting elements and
compounds of the sample and their relative
ratios
(iv)Crystallographic Information : The
arrangement of atoms in the specimen and
their degree of order

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How does the Scanning Electron
Microscope (SEM) work?
When the electron beam interacts with the specimen, the back scattered electrons
are emitted when electrons are bounced by the atoms and being reflected back
nearly 180°. These electrons can be used to differentiate different atomic
elements and its intensity is more for heavier elements.
Secondary electrons are also produced when the electron beam interacts with
specimen atoms and removes one of its electron with extra energy. These
reactions occur near the surface of the specimen, and they are used in
topographical study of the specimen. Higher energy electron drops into the place
of exposed secondary electrons and that causes an energy surplus in the atom,
which releases another low energy electron called Augur electron, which gives
compositional information about the specimen.
During the same process along with Augur electrons, X-rays are also emitted
which provide further information on the composition of the specimen. All the
above said electrons are detected by the electron detector and are converted into
light and fed to a photomultiplier through alight pipe along with X-rays which
modulate the brightness of the CRT output device.
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Diagram of
Scanning Electron Microscope(SEM)
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Application of SEM
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Scanning Electron Microscopes (SEMs) have a wide range of applications across
various fields:
1. Industrial Uses : SEMs are used in industries for quality control and failure
analysis.
2. Nanoscience Studies : SEMs play a crucial role in the study and
characterization of nanomaterials.
3. Biomedical Studies : SEMs are used to study biological specimens at a
microscopic level.
4. Microbiology : SEMs are used to analyze and study the very tiny filament
structures of microorganisms.
5. Cosmetic Industry : SEMs are used in the analysis of cosmetic components
which are very tiny in size.
6. Energy-Dispersive X-ray Spectroscopy : SEMs are used for spot chemical
analysis.

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Merits and Demerits:
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Merits:
1. Three-dimensional image of the object is obtained.
2. Object image has large depth of focus.
3. It can be used to examine specimen of large thickness.
4. Image can be viewed directly on the screen.
5. 3,00,000 times greater than that of the size of the object
magnification can be obtained.
Demerits:
1. The resolution of the image is limited to 10-20 nm, hence it is
very poor.

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Thank You