Scanning transmission electron microscopy

From Wikipedia, the free encyclopedia

You have new messages (last change).

A scanning transmission electron microscope (STEM) is a type of transmission electron microscope. With it, the electrons pass through the specimen, but, as in scanning electron microscopy, the electron optics focus the beam into a narrow spot which is scanned over the sample in a raster.

The rastering of the beam across the sample makes these microscopes suitable for analysis techniques such as mapping by energy dispersive X-ray (EDX) spectroscopy, electron energy loss spectroscopy (EELS) and annular dark-field imaging (ADF). These signals can be obtained simultaneously, allowing direct correlation of image and quantitative data.

By using a STEM and a high-angle detector, it is possible to form atomic resolution images where the contrast is directly related to the atomic number. This is in contrast to the conventional high-resolution electron microscopy technique, which uses phase-contrast, and therefore produces results which need interpretation by simulation.

[edit] History

Although the first STEM was built in 1938 by M. von Ardenne [1] [2], working in Berlin for Siemens. However, the results were inferior to that of TEM at the time, and von Ardenne only spent two years working on the problem. The microscope was destroyed in an air raid in 1944, and von Ardenne did not return to the field after WWII [3]

The technique did not become developed until the 1970s, with Albert Crewe at the University of Chicago developing the field emission gun [4] and adding a high quality objective lens to create the modern STEM, and demonstrated the ability to image atoms using ADF [5]

Atomic resolution chemical analysis using the STEM was first reported in 1993 (albeit in a paper later found to be flawed) [6][7]

[edit] See also

[edit] References

  1. ↑  von Ardenne, M (1938). "Das Elektronen-Rastermikroskop. Theoretische Grundlagen.". Z Phys 109: 553-572.
  2. ↑  von Ardenne, M (1938). "Das Elektronen-Rastermikroskop. Praktische Ausführung.". Z tech Phys 19: 407-416.
  3. ↑  [8]
  4. ↑  Crewe, Albert V, Isaacson, M. & Johnson, D. (1969). "[9]". Rev. Sci. Inst. 40: 241-246. DOI:10.1063/1.1683910.
  5. ↑  Crewe, Albert V, Wall, J. & Langmore, J. (1970). "Visibility of a single atom.". Science 168: 1338-1340.
  6. ↑ Browning, N. D., Chisholm M. F. & Pennycook S. J. (11). "Atomic-resolution chemical analysis using a scanning transmission electron microscope". Nature 366: 143-146. DOI:10.1038/366143a0.
  7. ↑ Browning, N. D., Chisholm M. F. & Pennycook S. J. (9). "Corrigendum: Atomic-resolution chemical analysis using a scanning transmission electron microscope". Nature 444: 235. DOI:10.1038/nature05262.
 This science article is a stub. You can help Wikipedia by expanding it.
Retrieved from "http://en.wikipedia.org../../../s/c/a/Scanning_transmission_electron_microscopy.html"
In other languages