Rapid and Inexpensive Sampling Technique for Emission Spectroscopic Analysis of Thin Films
Methods of analyzing thin solid films have recently been reviewed by Pliskin and Zanin.1 Their review shows that a good method for obtaining a fairly rapid survey analysis of a large number of impurities is emission spectroscopic analysis. When used for samples of which a sufficient quantity is available for analysis, this method yields excellent sensitivities for most of the more common impurities. For example, Addink2 described a method in which six 10-mg exposures are made of a material to determine the concentration of 70 elements with a limit of detection varying from 0.1 to 100 ppm by weight depending on both the mature of the sample and the element considered. In analyzing thin films, one is mostly confronted with the problem that less material is available than needed for reaching this sensitivity. Of course, a film with an area of 1 cm2, a thickness of 10 µ, and a density of 10 g cm−3 would furnish the required 10 mg per exposure, but often the films have thicknesses of 1 µ or less and their area and density is less than in this example. Known ways to increase the amount of material needed to improve the sensitivity to the level mentioned above are to prepare thin films of large area or to deposit thick films under virtually the same conditions as used for the thin films. In both cases the film is removed from the substrate and transferred to the graphite electrodes used for emission spectroscopy. This is often a tedious and time-consuming process, which almost inevitably causes loss of film material and/or contamination with impurities from the substrate. To circumvent interference from the substrate material, the use of a graphite substrate has been introduced because this is easily obtained in purity grades comparable to those of the graphite electrodes. 3, 4 Although this may certainly be a step in the right direction, it does not solve the problems of time-consuming removal procedures and the risk of contamination during this procedure.
KeywordsQuartz Graphite Carbide Silice Boron
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- 1.W. A. Pliskin and S. J. Zanin, in Handbook of Thin Film Technology,L. J. Maiesel and H. Glang, Eds. (McGraw-Hill, New York, 1970), Chap. 11.Google Scholar
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