” Everything in our terrestrial world depends on the motions of electrons… “

Axel Becke

Quick introduction to ARPES

ARPES (Angle-Resolved Photoemission Spectroscopy) is an experimental method to study the motions of electrons. Light is used to eject electrons from the material and they are counted as a function of direction, photon- and  kinetic energy.

Sketch of the photoemission process. Photons with energy hν are shone on the sample surface. Electrons are leaving with different kinetic energies (E) and are detected in a particular direction defined by two angles θ and φ.

Detected number of electrons can be plotted as a function of these four parameters in a number of ways:

a) Simplest dataset of the angle-resolved method, showing how intensity of photocurrent depends on direction when photon energy and kinetic energy are kept constant. Angle θ is chosen as an example. Any path in the directional space ( θ, φ ) can be considered. b) Another basic spectrum at constant photon energy – kinetic energy distribution in particular direction. It usually has an upper cutoff ( Emax ) in energy. c) Two-dimensional distribution in angular space, often recorded at maximal ( Emax ) kinetic energy. Can be obtained from a) by scanning φ. d) Intensity as a function of energy, as in b), but along arbitrary path in the directional space. e) The same, but photon energy is variable and kinetic one is fixed. f) This dataset is usually recorded at the normal emission ( θ, φ = 0 ). g) Three-dimensional distribution of intensity. Can be obtained from e) by scanning φ. h) Another 3D plot which can be obtained from d) by scanning φ.

Such intensity distributions provide direct access to the Fermi surface and electronic structure of the studied material. They can be used to calculate physical properties, identify chemical composition or characterize the quality of the surface.

We offer a simple and direct way to detect electrons using our FeSuMa spectrometer.

Learn more about ARPES, Fermi surface and electronic structure here.