100 Years of Work Function

This paper traces early inquires on the nature of the work function (WF). Much attention was paid to the papers published by Einstein (1905), Richardson (1901), Jentzsch (1908), Debye (1910), Schottky (1914) and Langmuir (1916). Those authors assumed that the image force, introduced already by Thomson for macroscopic bodies, may be the main reason for the barrier at the metal surface. The formula derived by Schottky (1914) is still used for calculation of the lowering of the surface barrier in presence of an external electric field. In further development of surface physics, however, much emphasis was paid to the role of a dipole layer. However, at the end of 20th century the idea of the image potential as the main contribution to WF was restored by Brodie (1995) and subsequently improved by Halas and Durakiewicz (1998). In these theories a distance d from which the image force can be integrated is found from the uncertainty principle and from the length of spontaneous metallic plasma polarization, respectively. The last approach has appeared to be very useful in calculation of WF of conducting compounds and ionization potentials of metallic clusters.