Work function

The work function is the minimum energy required to remove an electron from a material’s surface into vacuum. Its value depends on the material and the surface’s chemical and structural state.

Photoelectric effect: The emission of electrons from a material after it absorbs electromagnetic radiation. Its threshold frequency reveals the work needed to eject an electron.
Vacuum level: The energy of an electron at rest just outside a material, used as a reference in surface electronic structure. The work function is measured up to this external energy reference.
Schottky barrier: An energy barrier for charge carriers at a metal–semiconductor junction. The metal work function helps set the barrier at a semiconductor contact.
Ionization energy: The energy required to remove an electron from an isolated atom or molecule. Unlike work function, it concerns an isolated species rather than a material surface.
Einstein’s photoelectric equation: An equation relating photon energy, work function, and the maximum kinetic energy of photoelectrons. It expresses the work function as the energy left after photoelectrons escape.
Electron affinity: In a solid, the energy difference between the conduction-band minimum and the vacuum level. It uses the same vacuum reference but starts from the conduction band, not the Fermi level.
Metal–semiconductor junction: An interface between a metal and a semiconductor whose electrical behavior depends on band alignment. Work-function alignment helps determine charge transfer and contact behavior.
Band gap: The energy interval between a solid’s valence band and conduction band. A band gap separates states inside a solid; work function reaches from the Fermi level to vacuum.
Photoelectron spectroscopy: A family of techniques that infer electronic structure by measuring emitted electrons’ energies. Its energy measurements can determine a material’s surface work function.
Surface dipole: A separation of positive and negative charge across a surface that creates an electric potential step. This potential step can shift the vacuum level and alter the work function.

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