Transmission Electron Microscopy (TEM) utilizes a high-energy electron beam to produce detailed images of specimen morphology, composition, and crystallography with resolutions down to 0.2 nm. It operates mainly in two modes: diffraction mode, which helps identify crystalline structures, and image mode, which focuses on producing images. While TEM offers high resolution and detailed information, it requires less sample material, operates under high vacuum, is costly, and demands meticulous sample preparation.

1. TRANSMISSION ELECTRON
MICROSCOPY (TEM)
AISWARYA GOWRI V S
RESEARCH SCHOLAR
SRMIST KTR

2. CONTENT
INTRODUCTION
PRINCIPLE
COMPONENTS
WORKING
TRANSMISSION ELECTRON MICROSCOPY VS SCANNING
ELECTRON MICROSCOPY
ADVANTAGE AND DISADVANTAGE OF TRANSMISSION ELECTRON
MICROSCOPY

3. INTRODUCTION
Transmission electron microscopy was the first electron microscopy that used a high-
energy electron beam to generate morphology, composition, and crystallographic
information of a given sample.
* Resolution Magnification
Light
microscope
200nm 1000X
Transmission
electron
microscope
0.2 nm 20,00,000X

4. PRINCIPLE
Once the electron beam interacts with the specimen, they are either scattered or are
transmitted based on the mass and density ratio.
The transmitted electron beam will strike the fluorescent screen or a charge-coupled
device (CCD) camera, which will generate an image with varying contrast based on the
intensity of the electron beam.

5. COMPONENTS
Electron gun: Tungsten and Lanthanum- Hexaboride.
Condenser system: Focus the electron beam to sample.
Image producing system: consists of the objective lens,
aperture lens, and projection lens- (for magnification).
Image recording system: Fluorescent screen, or charge-
coupled device (CCD) camera.

6.  TEM can operate on two modes, Diffraction mode and image mode
1.Diffraction mode
 The objective lens forms a diffraction pattern in the back focal plane with electrons
scattered and diffracted by the sample and combines them to generate an image in the
image plane.
 Difraction mode can say whether the sample is single crystalline, poly crystalline, or
amorphous by taking Selective Area Diffraction (SAD).
 Single crystal: Produces diffraction pattern consist with a centre spot associated with
transmitted beam and other diffracted spot.
 Poly crystal:Produces diffraction pattern on the rings of different radius.
 Amorphus sample: Follows a halo ring pattern.
single crystall Poly crystall Amorphous

7. 2. Image mode
 Image of the sample is focused and projected onto the screen,
 Which is of two types Darkfield image and Bright field image.
 Bright field images: It is obtained by passing transmitted waves to the objective
aperture.
 Dark field images: It is obtained by allowing the diffracted beam to the objective
aperture.
Bright field image Dark field image

8. SEM Vs TEM
SEM TEM
 SEM shows only the morphology of samples.
 SEM can resolve objects as close as 20 nm.
 The magnifying power of SEM is up to 50,000X.
 SEM allows for a large amount of sample to be
analyzed at a time.
 Secondary or backscattered electrons arising from the
interaction of electron beam and metal-coated
specimen are collected and the resulting image is
displayed on a computer screen.
 TEM can show many characteristics of the sample,
such as internal composition, morphology, and
crystallization.
 TEM has a much higher resolution than SEM. It can
resolve objects as close as 1 nm i.e. down to near-
atomic levels.
 The magnifying power of TEM is up to 2 million
times.
 With TEM only a small amount of samples can be
analyzed at a time.
 Transmitted electrons hit a fluorescent screen giving
rise to a “shadow image” of the specimen with its
different parts displayed in varied darkness according
to their density. The image can be studied directly by
the operator and photographed with a camera.

10. ADVANTAGE
 Less sample is required.
 TEMs provide information on element and compound structure.
 TEMs are able to yield information of surface features, shape, size and structure.
DISADVANTAGE
 High vacuum is required.
 TEMs are large and very expensive.
 Laborious sample preparation.

11. Thank
you……