Materials Research Activities

History of electron microscopy

Electron microscopy

Read Tim Palucka's pages on the history of electron microscopy:

The electron microscope is integral to characterization of materials. Maybe more than 10,000 electron microscopes are in use across most disciplines in the natural sciences. In the electron microscope a beam of electrons is focused upon a target specimen. Information may be gathered from electrons transmitted through the specimen, from Bragg diffracted electrons, from Auger electrons, from characteristic x-rays, and from the charge absorbed by the specimen. An explanation of the workings of the electron microscopy at three levels (elementary, high school, college) can be found on the Iowa State Materials Science and Engineering Department's website (from where the image on the left is also taken).

The first operational electron microscope was presented by Ernst Ruska and Max Knoll in 1932, and 6 years later Ruska had a first version on the market. In 1986 Ruska received a Nobel Prize in physics for his "fundamental work in electron optics and for the design of the first electron microscope". The following table gives a basic outline of the history of the electron microscope by decades.

Year

Specimens

Application/development

Instrumentation/theory

Resolution
1940s

Replicas

  • oxide
  • carbon
  • plastics
  • surfaces
  • slip steps
  • extracted particles
  • fractography
  • 50kV, single condenser
  • little or no theory; a first basic theory of electron microscopy was published in 1949 by Heidenreich.
 ~10nm
1950s

Thin foils:

  • from bulk
  • deposited
  • defects
  • phase transitions
  • 100kV
  • contrast theory developed.
 ~0.5-2nm
1960s
  • metals
  • semiconductors
  • ceramics
  • minerals
  • Dynamic in-situ studies
  • substructure of solids
  • radiation damage
  • microdiffraction
  • high voltage electron microscopes (Toulouse: 1.2 and 3MeV)
  • scanning electron microscopes
  • accessories for in-situ studies
  • controlled experiments
  • 0.3nm (transmission)
  • ~15-20nm (scanning)
1970s
  • catalysts
  • quasicrystals
  • High resolution imaging
  • lattice imaging
  • Analytical transmission electron microscopy
  • scanning transmission electron microscopy
  • energy dispersive x-ray spectra
  • electron energy loss spectroscopy
  • commercial high voltage electron microscopy (0.4-1.5MeV)
  • high resolution imaging theory
  • 0.2nm (transmission)
  • 7nm (standard scanning)
1980s virtually all materials
  • atomic resolution in close-packed solids
  • surface imaging
  • small particles
  • commercial medium-voltage high-resolution/analytical electron microscopy (300-400kV)
  • improved analytical capabilities
  • energy filtering imaging
  • ultra-high vacuum microscopes
  • 0.15nm (transmission)
  • 5nm (scanning at 1kV)
1990s  
  • fast computation for image simulation
  • alloy design
  • nanostructures
  • integrated digital scanning and image processing
  • surface atomic microscopy
  • orientation imaging microscopy
  • 0.1nm (transmission)
  • 3nm (scanning at 1kV)
2000s        

Most of the information in the above table was taken from G. Thomas, "The impact of electron microscopy on materials research", in Impact of Electron and Scanning Probe Microscopy on Materials Research, edited by Rickerby, Valdre, and Valdre, Kluwer: 1999; and from Vander Voort & Friel (eds.), Development in Materials Characterization Technologies. The image on the right is also taken from the latter (Figure 1, page 45) by permission of ASM International, Materials Park, OH 44073-0002.

The use of the tree as a metaphor for the historical development is interesting. It is certainly suggestive, and as such it does not matter greatly whether the metaphor applies to all facets. The tree metaphor points, of course, to the undisputable fact that all specialized forms of electron microscopy could not have emerged without the already existing earlier forms. However, it also suggests parallels with an organism that seems less accurate. The small branches and leaves could be seen as having originated from many more sources than just the original SEM. There was also no predisposition (such as in a tree's DNA) to develop in just this fashion.
This page was written and last updated on 19 July 2002 by Arne Hessenbruch.