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The Colors of Silicon

Published online by Cambridge University Press:  14 March 2018

John McCaffrey*
Affiliation:
National Research Council of Canada

Extract

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When silicon samples are thinned and backlit, they display a series of colors; from deep red in the thicker (-5-10 μm) regions, to orange and yellow in thinner regions, to effectively transparent in the thinnest regions, This colorful effect can be used as a technique for monitoring the thickness of cross-sectional samples prepared for transmission electron microscopy (TEM).

As seen in Figure 1, a cross-sectional TEM sample of a thin, indium tin oxide (ITO) film on glass was being investigated, A sample was prepared for low-angle ion milling by the Barna method with the addition of an adjacent piece of silicon for a thickness indicator. The colors of silicon could then be monitored to indicate when the ITO/glass sample was thin enough for TEM examination. In the figure, the arrow indicates the region of interest on the ITO/glass sample. This figure was produced by photographing the entire TEM sample through an optical microscope, backlit with a standard quartzhalogen illuminator.

Type
Research Article
Copyright
Copyright © Microscopy Society of America 1999

References

1. Bama, A, (1992) Topographic kinetics and practice of low-angle ton beam thinning. In: Specimen Prep, for TEM of Materials - III. Mat, Res. Soc. Symp. Proc, Vol 254, eds. Anderson, R., Tracy, B. and Bravman, J., pp. 322.Google Scholar

2. McCaffrey, J.P., Barna, A.. “Preparation of TEM samples for low-angle ion milling”, Microscopy Research and Technique, 36(5), pp. 372377 (1997).3.0.CO;2-N>CrossRefGoogle ScholarPubMed

3. McCaffrey, J.P., Sullivan, B.T., Fraser, J.W., Callahan, D.L., “Use of color to calibrate the thickness of silicon samples during etching and thinning processes”, Micron, 27(6), pp. 407411,(1997).Google Scholar

4. McCaffrey, J.P. and Hulse, J.. “The use of transmitted color and interference fringes for thickness determination of silicon”, Micron 29(2-3). pp. 139144 (1998).Google Scholar