Kratos XSAM-800
Mika Valden
+358 3 3115 2555
1984
X-ray Photoelectron Spectroscopy known as XPS or ESCA (Electron Spectroscopy for Chemical Analysis) is based on the photoelectric effect, i.e. the sample is illuminated with X-ray photons that results in the ejection of photoelectrons from the surface. The binding energy of the photoemitted electrons carries the information on the elements from which they originate as well as the chemical bonding of the elements.For example, XPS can distinguish between the ionic and covalent forms of compounds, or whether a metal is in its oxidised or metallic state.
In XPS (X-ray Photoelectron Spectroscopy) the sample is exposed to an X-ray beam and the energies of characteristically emitted photoelectrons are measured by the electron analyser.
Due to the short inelastic mean free paths of the photoemitted electrons, electron spectroscopy measurements only analyse the outermost two through ten atomic layers of the surface. This means that electron spectroscopy is a surface sensitive analysis method. However, if the analysed region is embedded below the surface, ion etching can be used to remove the topmost atomic layers. High energy Ar ions remove atoms, ions and clusters from the topmost layers of the sample and the chemical composition of the uncovered material can again be determined by XPS. By repeated ion etching and XPS measurements (i.e. depth profiling), the depth distribution of the elements in the sample can be accurately determined.
Electron spectroscopy is sensitive to as low as 0.1 atom percent and detects elements except H and He. It is non-destructive and it can be applied to all solid materials, including insulators such as polymers and glasses.