Contact potential difference

Article By:

Nordman, James E. Department of Electrical and Computer Engineering, University of Wisconsin, Madison, Wisconsin.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.158800

An electrostatic potential that exists between samples of two dissimilar electrically conductive materials (metals or semiconductors with different electron work functions) that have been brought into thermal equilibrium with each other, usually through a physical contact. Although normally measured between two surfaces which are not in contact, this potential is called the contact potential difference. Its origin can be described in terms of the process necessary to bring the samples into equilibrium. Initially it is expected that mobile charge carriers (electrons or holes) will migrate from one sample to the other. If there is a net flow of electrons from material A to material B (see illustration), material B will become negatively charged and material A will become positively charged, assuming that they were originally neutral. This process is self limiting because a potential difference between the two samples will develop due to the charge separation and will grow to a value sufficient to stop further motion of the electrons from A to B.

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