Work Function: Fundamentals, Measurement, Calculation, Engineering, and Applications

The familiar work function (the energy barrier for an electron to move across a material's surface into the vacuum) is central to a vast array of surface and interfacial processes, and thus is fundamental to technologies ranging from vacuum and solid-state electronics to catalysis. Despite this importance, multiple issues associated with the varying vacuum level of electrons near surfaces often obscure how is being defined, measured, and used. This Review clarifies the definition of with extra care, summarizes recent approaches for calculating and predicting, and discusses how tuning bulk electronic structure and surface dipoles can be used to engineer.