Scanning Electron Microscopy (SEM) utilizes electron beams to produce high-resolution three-dimensional images of various specimens. It is instrumental in fields such as biology, forensics, and materials science, allowing for detailed investigations of sample surfaces and microstructures. While SEM offers significant advantages in terms of magnification and speed, it also has notable disadvantages, including high operational costs and extensive sample preparation requirements.

2. Scanning Electron Microscopy
Presented To:
Sir Zahid Qamar
Presented by:
Numair Zeeshan
Naeem Akhtar Khan

3. Outline
• Basic info
• Why we use SEM
• Principal
• Instrumentation
• Detection in Sem
• Working
• Application
• Advantages and Disadvantage

4. WhyWe Use SEM
• When we want to study a sample in a depth
• By using SEM create magnified image
• Sem has high resolution power
• Depth resolution 10 -100nm
• Lateral resolution 1-10nm

5. Electron Microscope
• Electron Microscope is a type of microscope that use a beam
of electron to create an image of specimen.
• Have a higher resolving power then light microscope and can
reveal the structure of smaller object.
• Electron are very sensitive to magnetic field and can
therefore control by changing the current through lenses.
• Use to investigate structure of wide range of biological and
inorganic specimen including cell microorganism etc.

6. Principle
•When accelerated
primary electron strikes
the sample it produces
secondary electron these
secondary electron are
collected by positive
charge electron detector
which in turn gives three-
dimensional image of the
sample.

7. SEM
Components
Electron Gun:
• Electron gun contain tungsten filament 1-
30kv accelerating voltage is applied to
produce electron beam.
Anode:
• It is a positively charged and attract with
negatively charged electrons and ultimately
this anode will accelerate velocity of the
electrons.
• Electron beam is controlled by condenser
lenses and object lenses these are
electromagnetic lenses.

8. • Electron beam is controlled by condenser lenses and object lenses
these are electromagnetic lenses
Condenser lenses:
• These lenses will focus electron beam toward, the objective
lenses.
Objective lenses:
• The lens will again focus the electron beam toward, the sample.

9. Detection in SEM
There is three types of detection is possible in SEM
Secondary electron detector
•SE ARE most abundant in the case of SEM and detected by
suitable detector ET detector are most commonly used for
detection secondary electron.
•ET detector contain Biased grid which is positively charged
to attract the secondary electron.This will create basic
image of sem.

10. BACKSCATTERD ELECTRON
•Energy of backscattered electron are higher then,
secondary electron so ET detector of verifying
voltage can differentiate betweenTHEM.
X-rays Detector
•Inside the sample holder x ray detector is placed
and it will detect x-ray imaged by sample.
•THIS detection process is known as EDX

11. Scanning process and images formation
Step 1
• A beam of electron is produced at the top of microscope by
heating of a metallic filament.
Step 2
• Electron beam a vertically path through column of microscope.
• It makes its way through electro magnetic lenses which focus
and direct the beam towards the sample.

12. Scanning process and images formation
Step 3
• Once it hit the sample other electron are ejected
from the sample.
• Detector collect secondary electron or
backscattered electron and convert them to a
signal that is sent to viewing screen like the one
is in an ordinary television producing an images .
• When the accelerated beam of electron strike a
specimen, they

13. Sample
preparation
Wash
Dry
Dehydration
(Acetone + Alcohol)
Coating

14. Scanning Electron Microscopy
(SEM)
•These microscopes can not be used to
image living cell
•Produces image of sample by scanning the
surface
(Any object biological or non biological)

15. Scanning Electron Microscopy

17. SEM Application
• SEMs have a variety of applications in a number of
scientific and industry-related fields, especially where
characterizations of solid materials is beneficial.
• For investigation of viruses, structure.
• 3D tissue imaging.
• Insect and other Micro-organism and Component
visualize.

18. • A SEM can detect and analyze surface fractures, provide
information in microstructures, examine surface
contaminations, provide qualitative chemical analyses and
identify crystalline structures.
• SEMs can be as essential research tool in fields such as life
science, biology, gemology, medical and forensic science,
metallurgy.
• In addition, SEMs have practical industrial and
technological applications such as semiconductor
inspection, production line of miniscule products and
assembly of microchips for computers.

20. Advantages of SEM
SEM are also easy to
operate with the proper
training and advances in
computer technology and
associated software make
operation user friendly
This instrument work fast,
often completing SEI, BSI
and EDS analysis in less
then 5 Minutes.
Magnifies object more
then 500000X
Most SEM sample require
minimal preparation
action.

21. Disadvantages of SEM
VERY LARGE
(OPERATED IN
SPECIAL ROOM).
PREPARATIONOF
MATERIAL IS
LENGTHY.
REQUIRE EXPERTISE EXPENSIVETO
PURCHASEAND
OPERATE.