SEM and TEM Principles_ Operation & Working with Schematics (1).pdf
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Basics of Microscopy
SEM and TEM Principles_ Operation & Working with Schematics (1).pdf
- 1. SEM and TEM Principles Operation & Working
- 2. Masters in Science – Physics, C-VLSI Ph.D in Physics - Processor Design using VLSI +91 9819110096 profarun@mes.ac.in Prof. Arun Shridharan Pillai Published Resarch and Technical Papers in Journals of Repute , Patents filed, Eminent Speaker at National and International Conferences , Funds from AICTE, DST and Govt of India. Delivered lectures on Entreprenuership, Idea Validation and Idea to Reality at various colleges and Universities. Designed unique programs such as MAKERTHON, IDEATHON, UNLOCK ENGINEERING , CONCEPTS BASED TEACHERS TRAINING IN PHYSICS,etc. Judge at Maharashtra Start-Up- Yatra
- 3. 01 Introduction CONTENTS 02 Scanning Electron Microscopy (SEM) Transmission Electron Microscopy (TEM) 03 04 Applications
- 4. Introduction A microscope is a tool used to magnify and examine objects that are too small to be seen with the naked eye, allowing scientists and researchers to study cells, microorganisms, and other minute structures in detail.
- 7. Electron microscopy is a technique for obtaining high- resolution images using a beam of electrons. It is crucial for detailed material and biological studies. Tracing its origins to the 1930s, electron microscopy has undergone significant advancements, enhancing resolution and paving the way for modern scientific miracles. Definition and Importance History and Development Overview of Electron Microscopy
- 9. S.N. Character Light Microscope Electron Microscope 1. Alternatively known as Optical microscope Beam microscope 2. Invented by Dutch spectacles makers Zacharius Jansen and his father Hans were the first to invent the compound microscope in the 16th century In 1931 physicist Ernst Ruska and German engineer Max Knoll. 3. Illuminating source Uses light (approx. wavelength 400-700 nm) to illuminate the objects under view. Uses a beam of electrons (approx equivalent wavelength 1 nm) to make objects larger for a detailed view. 4. Principle The image is formed by the absorption of light waves. The image is formed by scattering or transmission of electrons. 5. Structure Light microscopes are smaller and and lighter. Heavier and larger in size.
- 10. 6. Lenses used Lenses are made of glass. Lenses are made of electromagnets. 7. Vacuum Not used under a vacuum Operates under a high vacuum 8. Specimen type Fixed or unfixed, stained or unstained, unstained, living or non-living. Fixed, stained, and non-living. 9. Specimen observed Both live and dead specimens can be observed. Only dead specimens are possible to be observed. 10. Specimen preparation Less tedious and simple. It generally involves harsher processes, e.g. using corrosive chemicals. More skill required – both to prepare specimens and to interpret EM images (due to artifacts). S.N. Character Light Microscope Electron Microscope
- 11. 11. Preparation time Specimen preparation takes usually a few minutes to hours. Specimen preparation takes usually takes a few days. 12. Thickness of specimen 5 micrometer or thicker Ultra-thin, 0.1 micrometers or below 13. Dehydration of Specimen Specimens need not be dehydrated before viewing. Only dehydrated specimens are used. used. 14. Coating of specimen Stained by colored dyes for proper visualization. Coated with heavy metals to reflect electrons. 15. Mounting of specimen Mounted on the glass slide. Mounted on the metallic grid (mostly copper). S.N. Character Light Microscope Electron Microscope
- 12. Scanning Electron Microscopy (SEM)
- 13. 1 • SEM provides detailed surface images of specimens by scanning with focused electron beams, enabling studies in materials science and biology. • This microscope uses electrons as probe and wavelength of electrons is 0.1 Å. • SEM is used to obtain image of the surface of the object. • Electron beam in SEM is scanned over the surface of the object Scanning Electron Microscopy (SEM)
- 14. Construction of SEM The instrument used for SEM includes these components: •Electron source •Anode •Condenser lens •Scanning coils •Objective lens. An electron gun fires these beams, which then accelerate down the column of the scanning electron microscope. This ensures a high quality of imaging. The electrons interact with atoms on the surface of the sample. Detectors in the microscope pick up these signals and create high- resolution images displayed on a computer screen.
- 15. The electron source emits electrons, usually from a tungsten filament or field emission gun, which are focused into a narrow beam. Electron Source The scanning coil focuses the electron beam on a small spot on the specimen and also scans the surface. Scanning Coil Principle of SEM Operation
- 16. During this action, the electron beams pass through a series of lenses and apertures, which act to focus it. This occurs under vacuum conditions, which prevents and molecules or atoms already present in the microscope column from interacting with the electron beam. The vacuum also protects the electron source from vibrations and noise. The electron beams scan the sample in a raster pattern, scanning the surface area in lines from side to side, top to bottom. This interaction creates signals in the form of secondary electrons, backscattered electrons and rays that are characteristic of the sample.
- 17. The focused electron beam interacts with sample atoms, causing various signals that provide information about the sample’s surface. Electron Beam Interaction Secondary electrons are detected to form an image, which gives information about the sample's surface topography and composition. Detection of Secondary Electrons
- 18. Sample Preparation Beam Scanning Mechanism Image Formation Resolution and Magnification Samples must be properly prepared, often coated with a thin conductive layer to prevent charging and improve imaging. The electron beam scans across the sample in a raster pattern which allows the creation of a detailed image based on electron interactions. Images are formed from the signals generated by the electron- sample interactions, processed through detectors and displayed on a screen. SEM provides high resolution and magnification capabilities, enabling detailed visualization of sample morphology and surface structures. Working of SEM Sample Preparation Image Formation Samples must be properly prepared, often coated with a thin conductive layer to prevent charging and improve imaging. Images are formed from the signals generated by the electron- sample interactions, processed through detectors and displayed on a screen. SEM provides high resolution and magnification capabilities, enabling detailed visualization of sample morphology and surface structures.
- 19. Overview of the essential parts of a Scanning Electron Microscope, such as the electron gun, electromagnetic lenses, and detectors. Key Components Explanation of the electron's journey in an SEM, from being emitted by the electron gun to interacting with the sample surface. Electron Pathway Description of how the SEM is configured to obtain high- resolution images, including stage positioning and detector arrangement. Imaging Setup SEM Schematic Diagram
- 20. Transmission Electron Microscope A TEM image of a cluster of poliovirus. The polio virus is 30 nm in diameter.
- 22. Transmission Electron Microscopy • TEM uses a beam of electrons transmitted through a thin sample to form an image, offering high-resolution imaging of the internal structure of materials, including at the atomic level. • TEM offers insights into the internal structure of thin specimens, critical for analyzing cellular components and intricate material properties. • TEM can reveal stunning detail at the atomic scale by magnifying nanometer structures up to 50 million times.
- 23. High- energy electrons are transmitted through the sample, enabling visualization of internal structures at atomic levels not visible with light microscopy. Electron Beam Transmission As electrons interact with the sample, they are either scattered or transmitted, creating contrast and thus revealing detailed structural information of the sample. Interaction with Sample Principle of TEM Operation
- 24. Sample Preparation Samples must be ultra- thin, typically less than 100 nanometers, and may require staining or coating to enhance contrast and resolution. Image Detection The transmitted and scattered electrons strike a detector or photographic film, translating into detailed 2D images that can be analyzed for structural information. Working of TEM Electron Diffraction When electrons pass through the sample, they diffract, forming patterns that provide information about the crystal structure and atomic arrangement of the material.
- 26. ELECTRON GUN Responsible for producing electron beams. Electrons are produced by a cathode that is a tungsten filament that is V- shaped and it is normally heated. The tungsten filament is covered by a control grid known as a Wehnelt cylinder made up of a central hole which lies columnar to the tube. The cathode lies on top of or below the cylindrical column hole. ANODE The cathode and the control grid are negatively charged with an end of the anode which is disk-shaped that also has an axial hole. CONDENSER LENS It also has the condenser lens system which works to focus the electron beam on the specimen by controlling the energy intensity and the column hole of the electron gun. The TEM uses two condenser lenses to converge the beam of electrons to the specimen. The two condenser lens each function to produce an image i.e the first lens which has strong magnification, produces a smaller image of the specimen, to the second condenser lens, directing the image to the objectives.
- 27. IMAGE- PRODUCING SYSTEM Its made up of the objective lens, a movable stage or holding the specimen, intermediate and projector lenses. They function by focusing the passing electrons through the specimen forming a highly magnified image. The objective has a short focal length of about 1-5mm and it produces an intermediate image from the condenser which are transmitted to the projector lenses for magnification. The projector lenses are of two types, i.e the intermediate lens which allows great magnification of the image and the projector lens which gives a generally greater magnification over the intermediate lens. To produce efficient high standard images, the objectives and the projector lenses need high power supplies with high stability for the highest standard of resolution.
- 28. Image-Recording System Its made up of the fluorescent screen used to view and to focus on the image. They also have a digital camera that permanently records the images captured after viewing. They have a vacuum system that prevents the bombardment or collision of electrons with air molecules disrupting their movement and ability to focus. A vacuumed system facilitates the straight movement of electrons to the image. The vacuumed system is made up of a pump, gauge, valves and a power supply. The image that is formed is called a monochromatic image, which is greyish or black and white. The image must be visible to the human eye, and therefore, the electrons are allowed to pass through a fluorescent screen fixed at the base of the microscope.
- 29. Image-Recording System (contd..) •The image can also be captured digitally and displayed on a computer and stored in a JPEG or TIFF format. During the storage, the image can be manipulated from its monochromatic state to a colored image depending on the recording apparatus eg use of pixel cameras can store the image in color. •The presence of colored images allows easy visualization, identification, and characterization of the images.
- 30. Applications
- 31. Material Science SEM is extensively used to analyze the microstructure of materials, providing vital information on their composition, topography, and properties at a microscale. Biological Studies In biological studies, SEM helps visualize the surface details of biological specimens, like cells and microorganisms, aiding in understanding their structure and function. Applications of SEM
- 32. Nanotechnology TEM plays a crucial role in nanotechnology by allowing researchers to observe and manipulate nanomaterials at atomic resolutions, essential for developing new nanodevices. Crystallography TEM is vital in crystallography for studying the atomic structure and defects in crystals, which is key in materials science, solid- state physics, and chemistry. Industrial Applications TEM is used in various industries to analyze material properties and quality, contributing to advancements in semiconductor technology, metallurgy, and polymer sciences. Applications of TEM
- 33. Associate Prof & Academic Coordinator (FY ) Director- Business Development Pillai College of Engineering 10, Sector 16, New Panvel, Navi Mumbai Pin 410210 +91 9819110096 profarun@mes.ac.in Trendset Power and Technology Consultants Pvt. Ltd • Mumbai •Dubai • Muscat H. O 7th Floor , INSPIRE, Mayuresh Square CBD Belapur Pin 400614 +91 8433938445 arun@trendsettech.com Prof. Arun Shridharan Pillai