X-ray Photoelectron Spectroscopy (XPS) is a method for the qualitative and quantitative analysis of elements near the surface of a solid. The sample is irradiated with monochromatic X-rays, which leads to emission of electrons by atoms that are excited by these photons (photoelectric effect). Only photoelectrons from the outer 5 - 10 nm of the sample can leave without losing energy. A hemispherical energy analyzer is used to measure the kinetic energy of these electrons which is then recalculated in element specific binding energies. With XPS all elements (except for H and He) can be identified and quantified. Depending on the chemical surrounding of an element the binding energy can shift. This gives information about bonds or oxidation states. The detection limits depend on the element and are typically between 0.1 and 1 atom-%.

XPS can be used to determine the element composition on small spots (spot-Ø ≥ 10 µm) but also on areas with a size of a few square millimeters. Point analyses along a line across the surface (linescan), 2D-element distributions (maps) or angle resolved analyses (ARXPS) for the characterization of thin layers (< 10 nm) are common applications. It is also possible to determine the composition as a function of depth (depth profiling) by combining the XPS analysis with ion-induced sputtering. The method can be used for a variety of vacuum compatible samples (e.g. metals, glasses, wafers, polymers, foils, ceramics, pigments, catalysts, etc.).

Synonyms / Related Techniques

  • X-ray Photoelectron Spectroscopy (XPS)
  • Electron Spectroscopy for Chemical Analysis (ESCA)