Work function (electronics)

Article By:

Dekker, Adrianus J. Solid State Physics Laboratory, University of Groningen, Groningen, The Netherlands.

Last reviewed:June 2020

DOI:https://doi.org/10.1036/1097-8542.749500

A quantity with the dimensions of energy which determines the thermionic emission of a solid at a given temperature. The thermionic electron current density J emitted by the surface of a hot conductor at a temperature T is given by the Richardson-Dushman formula, J = AT² e^−ϕ/kT, where A is a constant, k is Boltzmann's constant (= 1.38 × 10⁻²³ joule per degree Celsius) and ϕ is the work function; the last may be determined from a plot of log (J/T²) versus 1/T. For metals, ϕ may also be determined by measuring the photoemission as a function of the frequency of the incident electromagnetic radiation; ϕ is then equal to the minimum (threshold) frequency for which electron emission is observed times Planck's constant h (= 6.63 × 10⁻ joule second). The work function of a solid is usually expressed in electronvolts (1 eV is the energy gained by an electron as it passes through a potential difference of 1 V, and is equal to 1.60 × 10⁻¹⁹ J). A list of average values of work functions (in electronvolts) for metals is given in the table.

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