Optical Microscope TEM SEM Scanning prob microscope

1. MICROSCOPY:
The science of Investigating small objects
Using such an instrument Is called microscopy.
The word "microscopy" comes from Greek
roots: mikros, small + skopeo, to view = to view small
(objects).
Microscopy is the technical field Of using
microscope to view objects and areas Of objects that
can’t be Seen with naked eye.In most materials the constituent grains are
of microscopic dimensions, having diameters that may
be on the order of microns (A micron sometimes called a
micrometer, is 10-6m) and their details must be

2. MICROSCOPE:
A microscope is an instrument
that can be used to observe
small objects, even cells. The
image of an object is
magnified through lenses in
the microscope. These lenses
bends light toward the eye and
makes an object appear larger
than it actually is.

3. Microscope
Optical microscope
Binocular stereoscopic
microscope
Brightfield microscope
Polarizing microscope
Phase contrast microscope
Differential interference
contrast microscope
Fluorescence microscope
Total internal reflection
fluorescence microscope
Laser microscope
Electron microscope
Transmission electron
microscope (TEM)
Scanning electron
microscope (SEM)
Scanning prob microscope
Atomic force microscope
(AFM)
Scanning near-field optical
microscope (SNOM)
Types of Microscope

4. MICROSCOPIC TECHNIQUES
Optical
microscopy
Electron
microscope
Scanning
prob
microscopy
Optical, electron, and scanning probe microscopes are
commonly used in microscopy.

5. MICROSCOPIC TECHNIQUES
Opticalmicroscopy
Figure 4.13 (a)
Polished and etched
grains as they might
appear when viewed
with an optical
microscope. (b) Section
taken through these
grains showing how the
etching characteristics
and resulting surface
texture vary from grain
to grain because of
differences in
crystallographic
orientation. (c)
Photomicrograph of a
polycrystalline brass
specimen. 60-
.
(Photomicrograph
courtesy of J. E. Burke,
General Electric Co.)
The visible part of
electromagnetic spectrum is the
type of radiation used by optical
microscopy.
Optical microscopy or
light microscopy is a common
microscopic technique oftenly
used in material Sciences as well
in life sciences.

6. Visible light occupies a very narrow portion of 400-700nm
between UV and Infrared radiation in the electromagnetic
spectrum.
Electromagnetic energy is complex, which is both wave
like and particle like.
The natural light we see is a complex mixture of
lights with different wavelengths, therefore almost all light
sources provide a mixture of wavelengths of light.

7. With optical microscopy, the light
microscope is used to study the
microstructure; optical and
illumination systems are its basic
elements.
. For materials that are opaque
to visible light (all metals and
many ceramics and polymers),
only the surface is subject to
observation, and the light
microscope must be used in a
reflecting mode.

8. • THE MAJOR IMAGING PRINCIPLE
OF THE OPTICAL MICROSCOPE IS
THAT AN OBJECTIVE LENS WITH
VERY SHORT FOCAL LENGTH IS
USED TO FORM A HIGHLY
MAGNIFIED REAL IMAGE OF THE
OBJECT.
WORKING PRINCIPLE OF
OPTICAL MICROSCOPE

9. SAMPLE PREPARATION
When preparing samples for microscopy, it is important
to produce something that is representative of the whole
specimen. It is not always possible to achieve this with a
single sample. Indeed, it is always good practice to mount
samples from a material under study in more than one
orientation. The variation in material properties will
affect how the preparation should be handled, for
example very soft or ductile materials may be difficult to
polish mechanically.

10. Cutting
•It important to be alert to the fact that preparation of a
specimen may change the microstructure of the material,
for example through heating, chemical attack, or
mechanical damage. The amount of damage depends on
the method by which the specimen is cut and the
material itself.
Cutting with abrasives may cause a large amount of
damage, whilst the use of a low-speed diamond saw can

11. Metal
working
Wood
working
Chemical-
mechanical
polishing
Flame
polishing
Vapour
polishing
Ultra-fine
abrasive
paste
polishing
Polishing
Polishing is the process of creating smooth and shiny
surface by rubbing it or using a chemical action leaving a
surface with a significant specular reflection.
The process of polishing with abrasive starts with coarse
ones and graduates to fine one.
Types

12. Etching
•Etching is used to reveal the
microstructure of the metal through
selective chemical attack. It also
removes the thin, highly deformed layer
introduced during grinding and
polishing.
•The rate of etching is affected by
crystallographic orientation, the phase

13. Electron microscopy (EM) is a technique for
obtaining high resolution images of material and non-
material (biological) specimens.
It is a versatile tool with a range of
methodologies to characterize the microstructural
features of a sample from 100pm to 100μm length
scales.
The high resolution of EM images results from the
use of electrons (which have very short wavelengths) as
the source of illuminating radiation. EM images provide
key information on the structural basis of materials.
Electron
Microscopy

14. TYPES OF ELECTRON MICROSCOPY
ElectronMicroscopy
Transmission Electron
Microscopy (TEM)
Bright Field (BF)
Dark Field (DF)
Electron Diffraction (ED)
Energy Filtered Transmission
Electron Microscopy (EFTEM)
High-Resolution Transmission
Electron Microscop (HRTEM)
Scanning Electron
Microscopy (SEM)
Bright Field (BF)
Dark Field (DF)
High-Angle Annular Dark
Field (HAADF)

15. TRANSMITTEDELECTRONMICROSCOPY TEM
The transmission electron microscope is a
very powerful tool for material science. A high energy
beam of electrons is shone through a very thin sample,
and the interactions between the electrons and the
atoms can be used to observe features such as the
crystal structure and features in the structure like
dislocations and grain boundaries. Chemical analysis
can also be performed. TEM can be used to study the
growth of layers, their composition and defects in
semiconductors. High resolution can be used to analyze
the quality, shape, size and density of quantum wells,

16. WORKING PRINCIPLE OF TEM
The TEM operates on the same
basic principles as the light
microscope but uses electrons
instead of light. Because the
wavelength of electrons is much
smaller than that of light, the
optimal resolution attainable for
TEM images is many orders of
magnitude better than that from a
light microscope. Thus, TEMs can
reveal the finest details of internal

17. SCANNING ELECTRONMICROSCOPE (SEM)
Scanning Electron Microscope is a type of Electron
microscope that produces image of a sample by scanning
it with a beam of electrons.
Magnifications ranging from 10 to in excess of
50,000 times are possible, as are also very great depths of
field.

18. WORKING PRINCIPLE OF SEM
Accelerated electrons in a SEM
carry significant amount of
kinetic energy, and this energy
is dissipated as a variety of
signals produce by electron-
sample interactions when the
incident electrons are
declarated in solid sample.
These signals include
secondary electrons that

19. TEMVS SEM
1. TEM is based on transmitted electrons while SEM is
based on scattered electrons.
2. TEM focuses on the internal composition whereas SEM
provides information about the sample‘s surface and
its composition.
Therefore TEM can show many characteristics of the
sample, such as morphology, crystalization, stress or
even magnetic domains. On the other hand, SEM shows
only the morphology of the sample.
3. TEM has much higher resolution than SEM.
4. TEM is used for imaging of dislocations, tiny
precipitates, grain boundaries and other defect structures

20. 5. In TEM, pictures are shown on flourescent screen
whereas in SEM, picture is shown on monitor.
6. TEM provides a two-dimensional picture whereas SEM
also provides a three-dimensional picture.

21. Scanningprob
microscopy
Scanning prob microscopy SPM is the name of a group
of microscopy techniques in which a physical probe (tip)
scans the sample. The interaction between the probe and
the sample is measured as a function of their relative
position.
SPM techniques are very versatile, and many types of
measurement can be performed depending on the kind
of interaction between the probe and the specimen.
SPM techniques include Scanning Tunnelling
Microscopy (STM), Atomic Force Microscopy (AFM),
Scanning Force Microscopy (SFM) and a multitude of

22. Some of the features that differentiate the SPM
from other microscopic techniques are as follows:
• Examination on the nanometer scale is possible
inasmuch as magnifications
As high as 109× are possible; much better
resolutions are attainable than with other
microscopic techniques.
• Three-dimensional magnified images are
generated that provide topographical information
about features of interest.
FEATURES

23. • Some SPMs may be operated in a
variety of environments (e.g.,
vacuum, air, liquid); thus, a
particular specimen may be
examined in its most suitable
environment.

24. THANKS