vakuumniveau

Vakuumniveau, or vacuum level, is the reference energy for an electron in vacuum just outside a material surface. It represents the energy an electron would have if it were free and at rest in vacuum, and it is used as an absolute energy reference in solid-state and surface science. In practice, Evac is treated as the energy zero to compare electronic states of different materials.

A central related quantity is the work function, the energy required to remove an electron from the material’s Fermi level to the vacuum level. In simple terms, the work function is the difference between the vacuum level and the Fermi level: it sets how strongly a material binds its electrons and how readily it can emit them. The vacuum level thus anchors the energies of electronic bands, defect levels, and surface states relative to a common external reference.

In heterostructures and interfaces, alignment of vacuum levels between materials can influence band offsets and charge transfer. Surface phenomena, such as dipole layers formed by adsorption or reconstruction, can shift the local vacuum level and modify work functions. External electric fields can also tilt the potential and change Evac near a surface.

Measurement and estimation of the vacuum level involve techniques such as photoemission spectroscopy (for example, ultraviolet photoelectron spectroscopy) to determine the work function and energy level positions, and Kelvin probe methods to assess contact potential differences. The concept is widely used in surface science, catalysis, semiconductor physics, and device engineering to understand and engineer energy alignment at interfaces. See also: work function, Fermi level, band alignment, photoemission spectroscopy.