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Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
Electron Microscope Shanthakumar
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Electron Microscope Shanthakumar

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  • 1. Electron Microscope
  • 2. Comparison b/w light and electron microscopes
    LIGHT MICROSCOPE
    ELECTRON MICROSCOPE
    Magnification can be done upto 2000 times
    Resolving power is less
    Photons are involved
    Magnificationcan be done upto 2 million times
    Have much greater resolving power than ordinary microscope
    Electrons are involved
  • 3. Scale
    3
  • 4. Reason for greater resolution and magnification of electron microscope
    Wavelength of an electron[de Broglie] is very much smaller than that of a light photon
    Wavelength of an electron = λ=h/(√2mE)
    Wavelength of a light photon = λ=h/E
  • 5. First Electron Microscope
    • Invented by Ernst Ruska
    • 6. Year-1933
    • 7. He was awarded the Nobel Prize for physics for his invention in 1986
  • Construction Of An Electron Microscope
  • 8. Construction of EM [TEM]
  • 9. THE ELECTRON GUN
  • 10. WORKING OF AN ELECTRON MICROSCOPE
  • 11. Types of ELECTRON MICROSCOPE
  • 12. TRANSMISSION ELECTRON MICROSCOPE
  • 13. TEM
    • Developed by ERNST RUSKA and MAX KNOLL in 1931 in germany
    • 14. It was the first type of electron microscope to be invented
  • When a beam of electrons is passed through a specimen , a part of it is transmitted and this part when projected on fluorescent screen , its image can be seen by the observer
    PRINCIPLE
  • 15. Construction and working
  • 16. TEM
    ELECTRON GUN
    ELECTROMAGNETIC LENSES
    VACUUM PUMPS
    OPENING TO INSERT SAMPLES
    OPERATION PANEL
    DISPLAY SCREEN
    WATER SUPPLY TO COOL THE INSTRUMENT
  • 17. ELECTRON GUN
    The electron gun produces a stream of monochromatic electrons of energy 100-400keV .
    The extraction of electrons is of two types
    1. Thermionic emission using thermal energy
    2. Field emission by applying very large electric field 1010 A/m
    FE gun is more expensive and must be used in high vacuum conditions.
  • 18. FIELD EMISSION GUN
  • 19. The beam of electrons is focused using condenser lenses [1&2]
    The beam is restricted by the condensor aperture
    Then it strikes the specimen and transmitted
    The transmitted portion is focused by Objective Lens into an image
    Intermediate and projector lenses enlarge the image
    Image is formed on phosphor screen
    Darker area – few electrons – thick region
    Lighter area – more electrons – thin region.
  • 20. Transmission electron microscopy
  • 21. Advantages
    • versatile technique for the characterisation of materials
    • 22. very high resolution
    • 23. Resolving power is
    • 24. Magnification is 1,000,000 times greater than the size of the object
    • 25. Information about crystal structure and chemical composition can be collected simultaneously
  • Disadvantages
    No 3-D image
    Aberrations due to lenses
    Absorption of electrons heats up the sample and changes its characteristics
    Larger current density[j] and hence more current I=jA {A- Illuminated area}
    Specimen must be thin because due to strong absorption of electrons , the penetration depth is small
  • 26. APPLICATIONS
    • In nano science , to find the internal structure of nanomaterials
    • 27. To get 2-D Image of biological cells , virus , bacteria etc.
    • 28. In fields such as thin film technology , metallurgy , microbiology etc.
    • 29. In studying the compositions of paints , alloys etc.
  • Scanning Electron Microscope
  • 30. The Scanning Electron Microscope
    • uses electrons reflected from the surface of a specimen to create image
    • 31. It captures the images of the specimen surface by scanning it with a high-energy beam of electrons , in a scan pattern
    • 32. produces a 3-dimensional image of specimen’s surface features
    24
  • 33. PRINCIPLE
    • The electrons interact with the atoms that make up the specimen, producing signals that contain information about its surface topography , composition and other properties such as electrical conductivity
  • CONSTRUCTIONPARTS of SEM
  • 34. SEM
    electron gun
    electromagnetic lenses
    vacuum pumps
    opening to insert specimen
    operation panel
    screen for display
    cryo – unit for cryosem
    electronic instruments
  • 35. PREPARATION OF SAMPLES
    • Samples must be electrically conductive
    • 36. If a non conductive material has to be viewed , then it has to be coated by a thin layer of electrically conductive material
    • 37. This coating is done using a sputter coater
  • GOLD COATED INSECT WHICH IS TO BE VIEWED THROUGH SEM
  • 38. SPUTTERING
  • 39. WORKING
    SEM produces signals in the form of secondary electrons , backscattered electrons, characteristic x-rays , light , specimen current, and transmitted electrons
    These signals are formed by the interaction of the electron beam with the surface of the specimen and require specialized detectors for their detection
    Depth of the specimen can be expressed in the image
    Back scattering of electrons help to detect the distribution of elements in the specimen
  • 40. CHARACTERISTIC X-RAY SIGNAL
    Characteristic x-ray signals are formed when the electron beam removes an inner shell electron of the sample causing a high energy electron to fill the space and release energy
    Help to identify the composition of elements in sample
  • 41. Scanning Electron Microscope
  • 42. ADVANTAGES OF SEM
    • used to examine specimens of large thickness
    • 43. Image can be directly viewed
    • 44. 3-Dimensional image can be obtained
    • 45. has large depth of focus
    • 46. very high magnification from x25 to x250,000
  • DISADVATAGES OF SEM
    • The Resolution of image is poor
    • 47. preparation of sample is difficult and tedious
    • 48. some samples can loose their structural property due to their interaction with the electrons
  • APPLICATIONS
    • Specimens of large thickness can be examined
    • 49. wide application in medical , science and engineering fields
    • 50. To find the structural composition of paper pulps, ceramic materials , polymers etc.
    • 51. Used to get 3-D image of biological cells, DNA , Bacteria etc.
  • Comparison
    SEM
    TEM
  • 52. SEM AND TEM PHOTOS
    SEM
    TEM
  • 53. Comparison of images
    SEM of the compound eye of a fly!
    TEM of bacteria
  • 54. Some more images obtained using SEM
    SEM of Yersiniapestis – which causes plague
    SEM image of Streptococcus pyogenes , which causes scarlet fever
  • 55. EM Image of the chloroplast of spinach
  • 56. EM Image of RBC
  • 57. SEM Image of a mesh
  • 58. RBC OF MAN
  • 59. NEURON CELL
  • 60. MOSQUITO
  • 61. CULTURED CELLS OF HUMAN BEING
  • 62. HUMAN CELLS
  • 63. HEAD OF A BLACK ANT
  • 64. Websites for further info:
    www.nobelprize.org
    www.wikipedia.com
    www.pbrc.hawaii.edu/microangela
    www.mos.org/sln/SEM/
    www.britannica.com/EBchecked/topic-art/183561/110970/Scanning-electron-microscope
  • 65. Presentation done by…
    SHANTHA KUMAR . T
    EEE
    RMD ENGG COLLEGE
  • 66. THANK YOU!

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