Specific Process Knowledge/Characterization/XPS/XPS technique: Difference between revisions
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[[File:800px-XPS_PHYSICS.jpg|700px| frameless|link=https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy|XPS principle. Image taken from wikipedia.]] | [[File:800px-XPS_PHYSICS.jpg|700px| frameless|link=https://en.wikipedia.org/wiki/X-ray_photoelectron_spectroscopy|XPS principle. Image taken from wikipedia.]] | ||
The | The analysis relies on the sequence: | ||
; The X-ray source | ; The X-ray source | ||
: In the X-ray gun, electrons are extracted from a filament and accelerated by a high voltage onto an aluminium anode. Here, much like the primary beam in an SEM, X-rays with the characteristic energy of aluminium (1486.7 eV) are generated. Emitted isotropically, some X-rays hit a quartz crystal that act as monochromator as the X-rays diffract on the crystal planes according to the Bragg equation. If curved, the crystal will also focus the beam of X-rays and in this way enable us to use X-ray spots (in the shape of ellipses) of different sizes - ranging from 400 µm to 40 µm. The smaller spots, however, only come at the price of a drastically lowered intensity - therefore it is generally advised only to use the default value of 400 µm unless strictly necessary for some reason. | : In the X-ray gun, electrons are extracted from a filament and accelerated by a high voltage onto an aluminium anode. Here, much like the primary beam in an SEM, X-rays with the characteristic energy of aluminium (1486.7 eV) are generated. Emitted isotropically, some X-rays hit a quartz crystal that act as monochromator as the X-rays diffract on the crystal planes according to the Bragg equation. If curved, the crystal will also focus the beam of X-rays and in this way enable us to use X-ray spots (in the shape of ellipses) of different sizes - ranging from 400 µm to 40 µm. The smaller spots, however, only come at the price of a drastically lowered intensity - therefore it is generally advised only to use the default value of 400 µm unless strictly necessary for some reason. | ||
; Generation of photoelectrons | |||
: As the incoming and monochromatic X-rays travels through the sample, they may react with electrons bound to atoms in the sample with a certain binding energy (E<sub>bind<\sub>) | |||
In the XPS spectrometer system the probed samples are irradiated by photons with a specific energy, and the photoelectrons that leaves the sample are detected. The energy levels of the electrons are elemental specific, and by measuring the energy of the outgoing electrons, it is possible to detect which elements that are present in a sample. | In the XPS spectrometer system the probed samples are irradiated by photons with a specific energy, and the photoelectrons that leaves the sample are detected. The energy levels of the electrons are elemental specific, and by measuring the energy of the outgoing electrons, it is possible to detect which elements that are present in a sample. | ||