Scanning transmission electron microscopy

Scanning transmission electron microscopy

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.

History

The first STEM was built in 1938 by Baron Manfred von Ardenne,ref|vA1ref|vA2 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.ref|vA3

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

Crewe and coworkers at the University of Chicago developed the cold field emission electron source and built a STEM able to visualize single heavy atoms on thin carbon substrates (Crewe et al., 1970).ref|Crewe2

Atomic resolution chemical analysis using the STEM was first reported in 1993.ref|Br1ref|Br2

Biological Application

The first application of this method to the imaging of biological molecules was demonstrated soon thereafter (Wall, 1971). At Brookhaven National Laboratory, STEM1 was designed (and built) by Joe Wall. The motivation for STEM imaging of biological samples is particularly to make use of dark-field microscopy, where the STEM is more efficient than a conventional TEM, allowing high contrast imaging of biological samples without requiring staining. The method has been widely used to solve a number of structural problems in molecular biology (Wall and Hainfeld, 1986; Hainfeld and Wall, 1988; Wall and Simon, 2001).

ee also

*Electron beam induced deposition
*Electron diffraction
*Electron energy loss spectroscopy (EELS)
*Electron microscope
*Energy filtered transmission electron microscopy (EFTEM)
*high-resolution transmission electron microscopy (HRTEM)
*Scanning confocal electron microscopy
*Scanning electron microscope (SEM)
*Scanning transmission electron microscope (STEM)
*Transmission Electron Aberration-corrected Microscope
* [http://people.ccmr.cornell.edu/~davidm/WEELS/index.html WEELS - Websource for Electron Energy Loss Spectra]
* [http://people.ccmr.cornell.edu/~davidm/useful/Optimizing%20your%20STEM.html Optimizing Your Microscope]
* [http://people.ccmr.cornell.edu/~davidm/Muller_tutorials.html Kavli Summer School on Electron Microscopy 2006: Fundamental Limits and New Science held at Cornell University, July 13-15, 2006.]
* [http://www.biology.bnl.gov/stem/stem.html Brookhaven STEM facility]

References

# cite journal
last = von Ardenne
first = M
year = 1938
month =
title = Das Elektronen-Rastermikroskop. Theoretische Grundlagen
journal = Z Phys
volume = 109
pages = 553–572
# cite journal
last = von Ardenne
first = M
year = 1938
title = Das Elektronen-Rastermikroskop. Praktische Ausführung
journal = Z tech Phys
volume = 19
pages = 407–416
# [http://www-g.eng.cam.ac.uk/125/achievements/mcmullan/mcm.htm D. McMullan, SEM 1928 - 1965]
# cite journal
last = Crewe
first = Albert V
coauthors = Isaacson, M. & Johnson, D.
year = 1969
title = A Simple Scanning Electron Microscope
journal = Rev. Sci. Inst.
volume = 40
pages = 241–246
doi = 10.1063/1.1683910
# cite journal
last = Crewe
first = Albert V
coauthors = Wall, J. & Langmore, J.
year = 1970
title = Visibility of a single atom
journal = Science
volume = 168
pages = 1338–1340
doi = 10.1126/science.168.3937.1338
pmid = 17731040
#cite journal
last = Browning
first = N. D.
coauthors = Chisholm M. F. & Pennycook S. J.
date = 11
year = 1993
month = November
title = Atomic-resolution chemical analysis using a scanning transmission electron microscope
journal = Nature
volume = 366
pages = 143–146
doi = 10.1038/366143a0
url = http://www.nature.com/nature/journal/v366/n6451/abs/366143a0.html
#cite journal
last = Browning
first = N. D.
authorlink =
coauthors = Chisholm M. F. & Pennycook S. J.
date = 9
year = 2006
month = November
title = Corrigendum: Atomic-resolution chemical analysis using a scanning transmission electron microscope
journal = Nature
volume = 444
pages = 235
doi = 10.1038/nature05262
url = http://www.nature.com/nature/journal/v444/n7116/full/nature05262.html


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