photoelectron spectroscopy abbr., PES (rus. спектроскопия, фотоэлектронная abbr., ФЭС) — a method to study electronic structure of occupied states on the surface and in the near-surface region of solids basing on analysis of energy spectrum of electrons generated by irradiation of the sample with photons as a result of the photoelectric effect.

Description

In the photoelectron spectroscopy (PES) method recorded electrons are emitted when the surface is irradiated with photons. The method is based on the photoelectric effect which means that a solid body's electrons, originally existing in a state with a binding energy , absorb photons with energy and escape from the solid body with kinetic energy where is the material's work function (see the Figure).

Photoelectron emission spectra contain information on the electronic levels of a material's atoms and enable one, with high accuracy, to identify the individual chemical elements present in the material.

Depending on the energy (wavelength) of photons used to excite electrons, photoelectron spectroscopy is usually divided in two types:

X-ray photoelectron spectroscopy (XPS) or electron spectroscopy for chemical analysis (ESCA) where X-rays with photon energies between 100 eV-10 keV are used (these values correspond to wavelengths from 10 to 0.1 nm) and which is applied to probe deep core levels;

ultraviolet photoelectron spectroscopy which uses photons in the ultraviolet spectral range of 10-50 eV (this corresponds to wavelengths from 100 to 25 nm) and which is applied to study the valence and conduction bands.

It should be noted that this division is rather notional, both in terms of the research object (since the division of energy levels into core and valence levels is pretty arbitrary) and radiation sources used (for example, by using synchrotron radiation we can study photoemission in the range from soft ultraviolet rays to hard X-rays).

Illustrations

Schematic diagram depicting photoemission on the metal surf
Schematic diagram depicting photoemission on the metal surface. Diagram shows the correlation between the density of completely filled electron states D(Ei) in a solid body and the photoemission spectrum I(Ek ). Peaks of elastic photoelectrons overlay continuous background of non-elastic secondary electrons [1].

Authors

  • Zotov Andrey V.
  • Saranin Alexander A.

Source

  1. Oura K. et al. Surface Science: An Introduction // Springer, 2010 - 452 pp.

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