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T he P rinciple of M icroscopy : SEM, TEM, AFM

Tuesday seminar. T he P rinciple of M icroscopy : SEM, TEM, AFM. 2014.02.25 So- Yeon Park vsoyounv@gmail.com. Contents. Introduction : Motivation for Microscopy Electron Microscopy - interaction with matter - SEM : S canning E lectron M icroscopy

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T he P rinciple of M icroscopy : SEM, TEM, AFM

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  1. Tuesday seminar The Principle of Microscopy : SEM, TEM, AFM 2014.02.25 So-Yeon Park vsoyounv@gmail.com

  2. Contents • Introduction : Motivation for Microscopy • Electron Microscopy - interaction with matter - SEM : Scanning Electron Microscopy - TEM : Transmission Electron Microscopy • AFM : Atomic Force Microscopy

  3. Motivation of microscopy Resolution of light microscope is limited ▶ possible magnification : ~ 2 000 Different approach : use electrons instead of light ▶ access to much smaller wavelengths ▶ electrostatic lenses instead of glass lenses ▶ possible magnification : ~ 2 000 000

  4. Interaction with matter

  5. Interaction with matter

  6. SEM Scanning Electron Microscopy

  7. Electrons for SEM image Secondary electrons (SE) Backscattered electrons (BSE)

  8. Electrons for SEM image Electron beam Electron beam

  9. Electrons for SEM image The intensity of emitted secondary electron for a line scan over some different surface features Edge effect

  10. Functional principle

  11. Functional principle

  12. Functional principle

  13. Functional principle

  14. Functional principle Electron detector

  15. Main concern of SEM High vacuum : to avoid crashing into air Edge effect

  16. Main concern of SEM Charging effect ▶ non-conductive material ▶ no electrons escaping from specimen ▶ Gold coating More electron Diffraction Au, Pd, Pt

  17. Gold coating EBT2 with Au coating Graduate School of Convergence Science and Technology. Seoul National University

  18. Example EBT2

  19. TEM Transmission Electron Microscopy

  20. Functional principle

  21. Functional principle

  22. Functional principle

  23. Functional principle

  24. Example Lung cell

  25. AFM Atomic Force Microscopy

  26. Principle Tip Position-sensitive photodetector Laser diode Cantilever spring Tip by measuring forces between a sharp probe (<10 nm) and surface at very short distance

  27. Mode of operation (1) Contact AFM < 0.5 nm probe-surface separation (2) Intermittent contact (tapping mode AFM) 0.5-2 nm (3) Non-contact AFM 0.1-10 nm

  28. Contact mode The force on the tip is repulsive. Advantage: fast scanning, good for rough samples Disadvantage : at time forces can damage/deform soft samples

  29. Intermittent mode(Tapping) The cantilever is oscillated at this resonant Frequency. Advantage: high resolution of samples that are easily damaged, good for biological samples Disadvantage : more challenging to image in liquids, slower scan speeds needed

  30. Non-contact mode The force on the tip is attractive. Advantage: VERY low force exerted on the sample, extended probe lifetime Disadvantage : lower resolution, usually need ultra high vacuum to have best imaging

  31. Limitations of AFM Used to study a wide variety of samples. The physical probe is not ideally sharp. An AFM image dose not reflect the true sample topography.

  32. Limitations of AFM For water droplet(물방울)

  33. Example Lung cell Collagen matrices EBT2 film

  34. Thank you for attention :D

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