Measurement of Work Function

Abstract

Main methods for measuring work function values are presented in this chapter. The methods are divided primarily into two categories based on the principle of the measurements; measurements of threshold energy to excite electrons at the Fermi level (absolute value measurements) and measurements of contact potential difference (relative value measurements). The principle of work function measurement for each method is presented with equations that relates a work function value to experimentally measured quantities. For each method, explanations are described on how to obtain a work function value from experimental data. Some examples of experiments are also demonstrated. Practical experimental tips in the measurements are also explained. Described methods of measuring threshold energy include measurements of thermal emission, field emission, and photoelectron emission, electron emission spectroscopy such as photoelectron emission yield spectroscopy, ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy. As the methods of measuring contact potential difference, Kelvin probe method and diode method are explained. In addition, as a unique method, obtaining a work function value from the binding energy of Xe absorbed on the specimen surface is explained.