Specific Process Knowledge/Characterization/XPS/XPS technique: Difference between revisions
| Line 5: | Line 5: | ||
=XPS technique= | =XPS technique= | ||
XPS is a surface sensitive and non destructive technique used for analysis of the elemental composition of a sample. It relies on the photoelectric effect; X-ray photons irradiated onto a sample will cause electrons bound in the sample atoms to become free electrons inside the the sample. The kinetic energy of these photoelectrons depend on the energy of the X-ray photon and their original binding energy. Escaping into the vacuum and counted in the electron spectrometer as function of their kinetic energy, the photoelectrons make a spectrum if represented in terms of numbers as function of their binding energy. There are two reasons why the technique is extremely useful: | XPS is a surface sensitive and non destructive technique used for analysis of the elemental composition of a sample. It relies on the photoelectric effect; X-ray photons irradiated onto a sample will cause electrons bound in the sample atoms to become free electrons inside the the sample. The kinetic energy of these photoelectrons depend on the energy of the X-ray photon and their original binding energy. Escaping into the vacuum and counted in the electron spectrometer as function of their kinetic energy, the photoelectrons make a spectrum if represented in terms of numbers as function of their binding energy. | ||
* The kinetic energy of the photoelectrons may be determined with such high accuracy (for instance, the resolution of the spectrometer is roughly 1 eV compared to the ~130 eV resolution of the spectrometer in an EDX X-ray detector ) that the small changes in binding energy of the sample electrons caused by the binding to other atoms. It is therefore possible to see | |||
* | |||
There are two reasons why the technique is extremely useful: | |||
* The kinetic energy of the photoelectrons may be determined with such high accuracy (for instance, the resolution of the spectrometer is roughly 1 eV compared to the ~130 eV resolution of the spectrometer in an EDX X-ray detector ) that the small changes in binding energy of the sample electrons caused by the binding to other atoms may be detected. It is therefore possible to see if elements are present as oxides, nitrides etc. | |||
* The inelastic mean free path of the photoelectrons is very short - as a result, photoelectrons from depths larger than some 10 monolayers will not contribute to the peaks as they have lost part of their kinetic energy. | |||
The basic principle is shown below (the image is taken from Wikipedia). | The basic principle is shown below (the image is taken from Wikipedia). | ||