SEM (SCANNING ELECTRON MICROSCOPY), Study Guides, Projects, Research of Nanotechnology

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SEM

(SCANNING ELECTRON

MICROSCOPE)

PRESENTED BY

D. ROHITH RAJ

CSE-1ST YEAR

SCANNING ELECTRON MICROSCOPE (SEM):

• SEM is a technique that provides information such as Topography, Composition, and Crystallography of an object. - TOPOGRAPHY: Describes the surface features of an object. - COMPOSITION: (^) Denotes the elements and compounds of an object and their relative amounts. - CRYSTALLOGRAPHY: Explains the arrangement of atoms in the object.

PRINCIPLE: The SEM operates on the basic principle of using a focused beam of high energy electrons to interact with sample, producing various signals that contain information about the sample surface and composition.

CONSTRUCTION:

All the lenses are electromagnetic lenses and devices that use a magnetic field to focus and control the beam of electrons

WORKING:

• A monochromatic electron beam is produced from the electron gun.
• The electron beam is allowed to fall on the first condenser lens and also transmitted through the first condenser lens.
• These rays are passing in such a way because of condenser aperature.
• The electron rays can move in all the directions, the condenser aperture helps to move the electron beam in such a way and allowed to pass on the secondcondenser lens.

SEM ANALYSIS:

• When a monochromatic electron beam is incident on the sample. They scattered in different directions.

• Some of them are scattered back and transmitted through the sample.
• The scattered and reflected electron beam on the top of the sample surface values are explained by using SEM.
• The bottom values are explained by using TEM (TRANSMISSION ELECTRON MICROSCOPE) 1. BACK SCATTERED ELECTRONS:
• When electron beam is incident on the surface and scattered back near to the incident electron. That electronsare called as Back Scattered Electrons.

3. AUGER ELECTRONS:

• During the emission of the secondary electrons, a lower energy electrons is released. Thus a vacency is present, that vacency is occupied by the higher energy electrons. The occupied electrons are called Auger electrons 4. X-RAYS:
• When higher energy electrons are jumped from vacency.That releases some energy that energy is called X-Rays.

ADVANTAGES:

• Provides detailed 3D Image.
• Easy to operate and software is user-friendly.
• It takes less than 5 minutes to analyse. DISADVANTAGES:
• It is Expensive and large in size.
• It should be area free from electric, magnetic and vibrational interferences.
• Sample must be Conductive.