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Conference Proceeding


Review of Progress in Quantitative Nondestructive Evaluation

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Chicago, IL


The four point direct current potential drop (DCPD) technique is used to measure electrical conductivity and crack depth. It is also used, together with Hall voltage measurements, to evaluate carrier concentration and mobility in semiconductors. Here the theory of DCPD is studied for planar structures in which edge effects may have to be taken into account and correction made to ensure accuracy. The current injected at a point on the surface of an infinite plate of finite thickness gives rise to a field that can be expressed as a summation derived using image theory. Because the images are periodic in the direction perpendicular to the plate surface, the field can also be conveniently expressed in the form of a Fourier series. The two basic formulas; image summation and Fourier series, can be modified for the case where the probe points are near the edge of a plate by further applying image theory and summing image∕Fourier terms in two dimensions. Both of these approaches agree with measurement results very well.


Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

This article appeared in AIP Conference Proceedings, 1096 (2009): 271–278 and may be found at:

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American Institute of Physics




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