Energy level of an electron positioned at rest just outside a solid, i.e. with zero kinetic energy with respect to the sample surface.
Notes: - ‘Just outside’ has also been written as “a few nanometers”, and is taken as a distance where there is no effect of image forces but that is sufficient for the electron to experience the full impact of the surface dipole.
- The vacuum level depends on the nature of the surface; for example, it is different between surface crystal planes \(\ce{Si}[001]\) and \(\ce{Si}[111]\).
Source:
PAC, 2020, 92, 1781. 'Glossary of methods and terms used in surface chemical analysis (IUPAC Recommendations 2020)' on page 1818 (https://doi.org/10.1515/pac-2019-0404)