The X-ray photoelectron spectroscopy or also photoelectron spectroscopy (XPS, often also electron spectroscopy for chemical analysis, ESCA) is a chemical analysis method that is characterized by secular surface sensitivity with a signal depth of around only 5 nm. X-ray bombardment produces photoelectrons whose energy allows conclusions to be drawn concerning the material composition on the basis of element-specific energy levels (all elements except H and He). Since the chemical environment of an atom influences the energy levels of the electrons, XPS also offers the possibility of making statements regarding bonding states, oxidation states or the proportion of different bonding partners.
XPS analysis provides information on chemical composition and bonding states near the surface and also allows depth profiles as a result of the integrated ion gun. XPS analysis is used, for example, in the following areas:
XPS spectra of a co-deposited 50nm Ni-Ag layer. There is a strong Ag signal at the surface (black). Below the surface (red, approx. 30nm ablated), the Ni signal predominates. The Ag has accumulated on the surface during layer deposition.
C-peak of an XPS measurement of PET film. The different bonding partners of the carbon atoms lead to peak splitting.