SEM Review

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Author:
saitclt
ID:
184108
Filename:
SEM Review
Updated:
2012-12-08 18:07:56
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SAIT CLT2 INST390
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Description:
Review for the SEM theory section
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  1. The name for the equation that relates resolution to wavelength
    • Abbes' Equation: smaller wavelength means smaller (better) resolution
    • d=0.621(wavelength)/n sin a
  2. TEM
    • Transmission Electron Microscope
    • Tunneling Electron Microscope
  3. Can a TEM produce a 3D image?
    No
  4. What is one main advantage of an SEM over a TEM?
    The SEM can produce 3D images
  5. Give 3 reasons to keep the column/sample chamber under vacuum
    • Increases the 'mean free path' of the electrons
    • The column stays cleaner
    • Prevents oxidation of the W filament
  6. What can happen to cells in a vacuum?
    They can rupture
  7. Name 2 alternatives for solving the problem of cells rupturing in a vacuum
    • 1. Use a partial vacuum (requires less preparation, but the quality of the images will not be as good)
    • 2. Preserve the sample and use critical point drying
  8. What type of metal is the filament made from?
    Tungsten
  9. Why should you set the filament temperature to the point of most effective saturation?
    Because this will emit the most electrons without overheating the filament and breaking it down
  10. The average distance an electron can travel before hitting something
    Mean Free Path
  11. Name the 2 types of lenses in the SEM
    • Condenser Lense
    • Objective Lense
  12. Which lense focuses electrons on the sample?
    The objective lense
  13. Which lense controls the intensity (number of electrons) in the beam?
    The Condenser Lense
  14. A ___ aperature size gives better resolution and depth of field
    smaller
  15. A __ scan spped gives better quality of image
    slow
  16. The mean free path must be ___ than the optical column
    longer
  17. Name the two types of pumps that make up the vacuum system. Which is more expensive?
    • Mechanical Pump
    • Diffusion Pump (more expensive)
  18. The term for the rotating stage
    Goniometer
  19. Name the 3 types of electron/sample interactions we focus on
    • Primary backscatter
    • Secondary electrons
    • X rays
  20. Which type of interactions allow us to get topographic (surface) information?
    • Primary backscatter
    • Secondary electrons
  21. Which type of electron/sample interaction has elastic collisions?
    Primary backscatter
  22. Which type ofelectron/sample interaction has inelastic collisions
    Secondary electrons
  23. Which type of electron/sample interaction allows us to get elemental composition information
    X rays
  24. SE
    Secondary Electrons
  25. BSE
    Back Scatter Electrons
  26. Amalgam
    An alloy of mercury with another metal
  27. Which detectors are retractable?
    • BSE
    • EDS
  28. Which detector gives clearer 2D images? (BSE or SE)
    BSE
  29. Which detector gives good 3D images?
    SE (secondary electron detector)
  30. EDS
    Energy Dispersive Spectroscopy
  31. Does EDS rely of X-ray fluorescene or X-ray diffraction?
    Fluorescence
  32. Increased accelerative voltage generally gives ____ resolution
    increased
  33. Atomic number contrast is associated with which detector?
    BSE
  34. In atomic number contrast, areas with high average atomic number appear ___ while areas with low average atomic number appear ___
    • Brighter
    • darker
  35. Where are the scanning coils located?
    In the optical column
  36. X ray microanalysis is another name for
    EDS

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