it can give you the brief view about the effects and lense used for electron microscope i.e. SEM,TEM,electron scattering,tunnel effect,electrostatic lens and magnostatic lens

1. NANOTECHNOLOGY
PREPARED BY-
KASHISH MANGAL(21112036)
KAVYA GUPTA (21112038)
NAMAN BAGGA(21112050)
SHIKHA GAUTAM(21112077)
GUGULOTHU AKHIL(21112022)
DR.B.R. AMBEDKAR NATIONAL INSTITUTE OF
TECHNOLOGY

2. INDEX
 Electron Scattering
 Electrostatic Lens
 Tunnel Effect
 Magnetostatic Lens
 SEM
 TEM

3. ELECTRON SCATTERING
o This effect is used in electron microscope.
o Electron scattering refers to the electron
changing the path after hitting some other
small particle like nucleus of an atom or another
electron.

4. e-
Electron Scattering

5. Electrostatic Lens
• Electrostatic lens work on the principle of
ELECTROSTATIC FOCUSSING.
• When electron travels through non-uniform
electric field they Experience the change of
motion or the change in path.
• We can use this type of lenses in electron
microscope.

6. Focal Point
Electron beam
V2>V1
T2
BRAGG’S LAW

7. Tunnel Effect
• Tunnel effect is defined as
the quantum mechanical
effect in which a particle can
penetrate a potential barrier
even it does not have the
energy to penetrate it.
• It is a quantum mechanical
phenomenon where
a wavefunction can
propagate through potential
barrier.
An electron wavepacket directed
at a potential barrier. Note the
dim spot on the right that
represents tunneling electrons.

8. Tunnel Effect
• Tunneling cannot be directly perceived.
Much of its understanding is shaped by
the microscopic world, which classical
mechanics cannot explain
• Classical mechanics predicts that particles
that do not have enough energy to
classically surmount a barrier cannot
reach the other side.
• The reason for this difference comes from
treating matter as having properties of
waves and particles.

9. APPLICATIONS
• Quantum tunnelling has important implications on
functioning of nanotechnology. It also plays role in nuclear
fusion, tunnel diode, quantum computing etc.
• Scanning tunneling microscope- The scanning tunneling microscope
(STM), invented by Gerd Binnig and Heinrich Rohrer, may allow imaging of
individual atoms on the surface of a material. It operates by taking advantage of
the relationship between quantum tunneling with distance. When the tip of the
STM's needle is brought close to a conduction surface that has a voltage bias,
measuring the current of electrons that are tunneling between the needle and
the surface reveals the distance between the needle and the surface. By
using piezoelectric rods that change in size when voltage is applied, the height
of the tip can be adjusted to keep the tunneling current constant. The time-
varying voltages that are applied to these rods can be recorded and used to
image the surface of the conductor.

10. Magnetostatic Lens
• Magnetic fields which are axially
symmetric have focusing effect on an
electron beam passing through them.
• The axially symmetric magnetic fields are
produced by short solenoids.
• By encasing the coils in hollow iron
shield, the magnetic fields are
concentrated an improved focusing
action is obtained.
• Such solenoid is called Magnetic Lenses.

11. Working of Lens
• We know that an electron travelling at an angle theta into
the field describes helical path. The motion is resultant of
translational motion along field direction and circular
motion in a plane perpendicular to the field, the radius of
path described is R=mvsintheta/Be
• From this equation, it is seen that radius of loop decreases
as electron moves into stronger field.
• In the similar way, while travelling through solenoidal field,
the helical path of electron is twisted into loops and
become smaller and electron comes to a point focus.
• With the adjustment of current through the solenoid and
initial accelerating voltage of electron the focal distance of
magnetic lens can be adjusted.

12. SEM(Scanning Electron Microscope)
• It is a type of electron microscope.
• Resolving power of SEM is greater than Light
microscope .
• Sample preparation –
1. Washing
2. Drying
3. Dehydration
4. Coating
• Live cells can’t be visualized

13. WORKING

21. ADVANTAGES
• Resolution of the order of few nanometers.
• Information about the elements and compounds in
the sample and their relative abundance.
• Biological specimen like pollen grains can be
studied.
• Corroded payer on metal surfaces can be studied.
DISADVANTAGE
• SEM can produce the image of a surface only a few
nano meter deep

22. APPLICATIONS
•For investigation of virus structure
•3D tissue imaging
•Insect, spore, other microorganism, or cellular
component visualize.
•Geologist often use SEM to learn more about
crystalline structure.
•Industries including microelectronics, medical
devices, food processing, all use SEM as a way to
examine the surface composition of component and
products.

23. TEM(Transmission Electron Microscopy)
• TEM is a technique of choice for analysis of Internal
microstructures.
• TEM is also used for evaluation of nano- structures
like fibers ,particles or microstructures of cell.
• It was invented by- Max Knoll and Ernst Ruska.

24. Principle of TEM
• Electrons those are passed through the sample or
specimen are imaged and gives the idea about the
internal structure of the sample
• Electrons submitted through the sample will strike into
the fluorescence Screen/plate and it will be converted
into image which is 2D and black and white.
• Electron Gun is used to produce electron beam and
operated at 1-30 Kv (For SEM) and 80-300 Kv (For TEM)
• Tungsten Filament is used in Electron Gun which
emits beam of electrons at very high voltage.

25. Main Parts of TEM
1. Electron Gun – Tungsten filament is used for
production of Electron Beam in Electron Gun.
2. Condenser Lenses- They are electromagnetic
lenses and they will focus all the electron beam
towards the specimen/sample.
In TEM, number of condenser lenses are very
much higher as compared to SEM. So electron beam
will be more accelerated and it can easily penetrate
the specimen.

26. Main Parts of TEM
3. Objective Lenses- It is also an electromagnetic lens
and focus for transmitted beam towards the projector
lenses.
4. Projector Lenses- It will magnify the transmitted
beams coming from the objective lens and focused
towards the fluorescent screen or CCD(charged
couple detector).
• CCD will send the data to the CPU
• TEM is operated under vacuum to reduce any
kind of interference by air.

27. Main Parts of TEM

28. APPLICATIONS
1. TEMs provide topographical, morphological,
compositional and crystalline information.
2. The images allow researchers to view samples
on a molecular level, making it possible to
analyze structure and texture.
3. Cancer research studies of tumor cell
ultrastructure.

29. ADVANTAGES
• TEMs offer very powerful magnification and resolution
• TEMs provide information on element and
compound structure
• Image are high quality and detailed
DISADVANTAGES
• TEMs are large and very expensive
• Laborious sample preparation
• Operation and analysis requires special training
• TEMs require special housing and maintenance.
• Images are black and white
• Require high vacuum

30. THANK
YOU!!!