Specific Process Knowledge/Characterization/XPS/XPS technique: Difference between revisions

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 ; Generation of photoelectrons
-: As the incoming and monochromatic X-rays (with energy E<sub>phot</sub>) impinge on and travel through the sample, they may react with electrons bound to atoms in the sample with a certain binding energy (E<sub>bind</sub>). The result is free electron inside sample with a kinetic energy (E<sub>kin</sub>=E<sub>phot</sub>-E<sub>bind</sub>) that is characteristic of the atomic level it originated from. The small energy changes in the electronic states induced by the formation of chemical bonds are also detectable by the XPS.
+: As the incoming and monochromatic X-rays (with energy E<sub>phot</sub>) impinge on and travel through the sample, they may react with electrons bound to atoms in the sample with a certain binding energy (E<sub>bind</sub>). The result is free electron inside sample with a kinetic energy (E<sub>kin</sub>=E<sub>phot</sub>-E<sub>bind</sub>) that is characteristic of the atomic level it originated from. As the binding energy depends on the small energy changes in the electronic states induced by the formation of chemical bonds, the electron also carries information about the chemical state.
+; Transport towards the vacuum
+: The inelastic mean free path of the photoelectrons is very short.
+; Detection in the analyzer
+This causes all electrons undergo inelastic collisions with sample electrons and a tail of
 == X-ray Photoelectron Spectroscopy analysis (XPS) ==
-Since the energy of the incoming photons is known, and the energy of the ejected electrons is measured, the binding energy of the electrons in the probed atoms can be determined. The binding energy of the electrons are element specific, and is therefore a "finger-print" of the atom. Hence, a measurement of the XPS spectrum gives information of which materials are present in the sample, and at which concentrations.
-XPS is an excellent technique to probe the chemical state of atoms on a surface. The binding energy of lower lying atomic levels (for example 1s, 2s and 2p) are at a specific energy, but is slightly affected by the chemical environment of the probed atom. This is known as the '''chemical shift'''. By measuring the shift of the electron binding energies one can determined the chemical state of atoms. See an example on the page [[Specific Process Knowledge/Characterization/XPS|XPS-ThermoScientific]].