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  1. Detection systems part 2

  2. Course outline

  3. Scale

  4. SEM and TEM

  5. Electron microscope • electrons scatter when they pass through thin sections of a specimen • transmitted electrons (those that do not scatter) are used to produce image • denser regions in specimen, scatter more electrons and appear darker

  6. Transmission electron microscope

  7. Transmission electron microscope

  8. Transmission electron microscope • Provides a view of the internal structure of a cell • Only very thin section of a specimen (about 100nm) can be studied • Magnification is 10000-100000X • Has a resolution 1000X better than light microscope • Resolution is about 0.5 nm • transmitted electrons (those that do not scatter) are used to produce image • denser regions in specimen, scatter more electrons and appear darker

  9. Transmission electron microscope

  10. Transmission electron microscope

  11. TEM of a plant cell

  12. TEM of outer shell of tumour spheroid

  13. Scanning electron microscope • No sectioning is required • Magnification is 100-10000X • Resolving power is about 20nm • produces a 3-dimensional image of specimen’s surface features • Uses electrons as the source of illumination, instead of light

  14. Scanning electron microscope

  15. Scanning electron microscope

  16. Scanning electron microscope

  17. Contrast formation Incident Electron Beam Contrast

  18. Ribosome

  19. Ribosome with SEM

  20. SEM of tumour spheroid

  21. Scanning electron microscope

  22. Fly head

  23. STM and AFM

  24. Scanning probe microscopes • Characteristics of common techniques for imaging and measuring surface morphology from http://www.di.com/

  25. Contact Mode AFM TappingMode™ AFM Non-contact Mode AFM Force Modulation Lateral Force Microscopy (LFM) Scanning Thermal Microscopy Magnetic Force Microscopy (MFM) LiftMode Phase Imaging Scanning Capacitance Microscopy Electric Force Microscopy (EFM) Nanoindenting/Scratching (IMHO) Scanning Tunneling Microscopy (STM) Lithography Scanning techniques

  26. Scanning probe microscopes Type Properties used for scanning Resolution Used for STM Tunneling Current between sample and probe Vertical resolution < 1 Å *Lateral resolution ~ 10 Å => Conductors => Solids SP Surface profile Vertical resolution ~ 10 Å *Lateral resolution ~ 1000 Å • Conductors, insulators, semiconductors => solids AFM Force between probe tip and sample surface (Interatomic or electromagnetic force) Vertical resolution < 1 Å *Lateral resolution ~ 10 Å => Conductors, insulators, semiconductor => liquid layers, liquid crystals and solids surfaces MFM Magnetic force Vertical resolution ~ 1 Å *Lateral resolution ~ 10 Å => Magnetic materials SCM Capacitance developed in the presence of tip near sample surface Vertical resolution ~ 2 Å *Lateral resolution ~ 5000 Å => Conductors => Solids

  27. Scanning probe microscopes • using scanning probe microscopes it is possible to image and manipulate matter on the nanometer scale • under ideal conditions its is possible to image and manipulate individuals atoms and molecules • this offers the prospect of important new insights in to the material world • this offers the prospect of important new products and processes

  28. Scanning tunneling microscopes • using a scanning tunneling microscope it is possible to image individual nickel atoms

  29. Scanning tunneling microscopes • it is also possible to manipulate individual iron atoms on a copper surface

  30. Scanning tunneling microscopes • it is also possible to have some fun Iron on copper Carbon monoxide on platinum

  31. Scanning tunneling microscopes • it is also possible to have some fun Xenon on nickel

  32. Atomic force microscope • With an atomic force microscope it is possible to image the carbon atoms of a carbon tube.

  33. Atomic force microscope • Or manipulate carbon tubes.

  34. Atomic force microscope • Or have some fun again.

  35. Scanning probe microscopes • thescanning tunnelling microscope (STM) is widely used to obtain atomically resolved images of metal and other conducting surfaces • this is very useful for characterizing surface roughness, observing surface defects, and determining the size and conformation of aggregates of atoms and molecules on a surface • increasingly STM is used to manipulate atoms and molecules on a surface • Roher and Binnig won the Nobel Prize in 1986 for their work in developing STM

  36. Scanning probe microscopes • a conducting tip is held close to the surface • electrons tunnel between the tip and the surface, producing an electrical signal • the tip is extremely sharp, being formed by one single atom • it slowly scans across the surface at a distance of only an atom's diameter

  37. Scanning probe microscopes • the tip is raised and lowered in order to keep the signal constant and maintain the distance • this enables it to follow even the smallest details of the surface it is scanning • by recording the vertical movement of the tip it is possible to study the structure of the surface atom by atom

  38. Scanning probe microscopes • a profile of the surface is created • from that a computer-generated contour map of the surface is produced • limited to use with conducting substrates • this limitation was addressed by atomic force microscopy Logic gate

  39. First atomic force microscope G. Binnig, Ch. Gerber and C.F. Quate, Phys. Rev. Lett. 56, 930 (1986)

  40. Atomic force microscope

  41. Atomic force microscope • theatomic force microscope (AFM) is widely used to obtain atomically resolved images of non-metal and other non-conducting surfaces • this is very useful for characterizing chemical and biological samples • increasingly AFM is used to manipulate macromolecules and cells on a surface • Bennig, Quate and Geber are credited with developing AFM and have received many major awards

  42. Atomic force microscope • an AFM works by scanning a ceramic tip over a surface • the tip is positioned at the end of a cantilever arm shaped like a diving board • the tip is repelled by or attracted to the surface and the cantilever arm deflected • the deflection is measured by a laser that reflects at an oblique angle from the very end of the cantilever

  43. Atomic force microscope

  44. Atomic force microscope

  45. Atomic force microscope

  46. Atomic force microscope • Micofabricated cantilever beams and probe tips for AFM.