Scanning and transmission electron microscopy

introduction
scanning electron microscopy
transmission electron microscopy

1. Scanning and Transmission electron microscopy Presented by, Parmar Nirali M. MSC.sem-2 Botany CBO-406 Department of life Ssciences H.N.G.U. Patan .

2. Content Introduction Scanning electron microscopy - principle - Application Transmission electron microscopy - principle - Application

3. INTRODUCTION Electron microscopes are scientific instruments that use a beam of energetic electrons to examine objects on a very fine scale. Electron microscopes were developed due to the limitations of light microscopes which are limited by the physics of light. In the early 1930 's this theoretical limit had been reached and there was a scientific desire to see the fine details of the interior structures of organic cells (nucleus, mitochondria..etc).

4. This required 10000 x plus magnification which was not possible using optical microscopes. This examination can yield information about the topography, morphology, composition and crystallographic information. Mainly 2 types:- - Transmission Electron Microscope(TEM):- Allows one the study of the inner structures. -Scanning Electron microscope (SEM):- Used to visualize the surface of objects.

5. Scanning Electron Microscopy What is SEM ? - An electron microscope that produces images of a sample by scanning over it with a focused beam of electrons. - The incident electrons interact with electrons in the sample, producing various signals that can be detected and contain information about the sample 's surface topography and composition.

6. Principle of SEM A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals known as secondary electrons that contain information about the samples surface topography and composition. SEM can achieve resolution better than 1 nanometre . Specimens can be observed in high vacuum, in low vacuum, in wet conditions (in environmental SEM) and at a wide range of cryogenic or elevated temperatures.

7. Application of SEM SEMs have a variety of applications in a number of scientific and industry- related fields, especially where characterizations of solid materials is beneficial. In addition to topography, morphological and compositional information, a scanning electron microscope can detect and analyze surface fractures, provide information in microstructure, examine surface contamination, reveal spatial variations in chemical analyses and identify crystalline structures. Generate X- rays from samples for microanalysis. Image morphology of samples. Image compositional and some bonding differences.

8. Virology - for investigations of virus structure. Cryo -Electron microscopy - Images can be made of the surface of frozen materials. 3D tissue imaging :- - Helps to know how cells are organized in a 3D network. - Their organization determines how cells can interact . SEM renders detailed 3D images. - extremely small microorganisms. - anatomical pictures of insect, worm, spore or other organic structures.

9. Transmission Electron Microscopy What is TEM ? - Transmission Electron microscopy uses high energy electrons (up to 300 kv accelerating voltage) which are accelerated to nearly the speed of light. - The electron beam behaves like a wavefront with wavelength about a million times shorter than lightwaves .

10. Principle of TEM The TEM operates on the same basic principles as the light microscope but uses electrons instead of light. When an electron beam passes through a thin section specimen of a material, electrons are scattered. A sophisticated system of electromagnetic lenses focuses the scattered electrons in to an image or a diffraction pattern, or a nano - analytical spectrum, depending on the mode of operation.

11. Application of TEM The main application of a transmission electron microscope is to provide high magnification images of the internal structure of a sample. Being able to obtain an internal image of a sample opens new possibilities for what sort of information can be gathered from it. A TEM operator can investigate the crystalline structure of an object, see the stress or internal fractures of a sample , or even view contamination within a sample through the use of diffraction patterns, to name just a few kinds of studies.

12. TEM is ideal for a number of different fields such as life sciences, nanotechnology, medical, biological and material research, forensic , analysis , gemology and metullurgy as well as indstry and education. The information is useful in the study of crystals and metals , but also has industrial application. The images allow researchers to view samples on a molecular level, making it possible to analyze structure and texture.

13. REFERENCES Principle and Techniques of Biochemistry and molecular Biology by :- Keith Wilson - John Walker https://en.m.wikipedia. org https://www.difindout. com

14. Thank you