X-ray Photoelectron Spectrometer, XPS

Laboratory: O-S20


X-ray Photoelectron Spectrometer from SPECS equipped with the following additional devices:


FOCUS 500 - X-ray source,
PHOIBOS 100 MCD-5 - 100 mm hemispherical analyzer,
IQE 11/35 - ion gun for low-energy ions of inert and reactive gases (0.3-5 keV),
LN2 - 800oC - precise XYZ manipulator samples holder with controlled heating and cooling,
turbo pump (Pfeiffer) and titanium sublimation pump (Hositrad) for the main chamber,
turbo pump (Pfeiffer) for prechamber,
• sealed water cooling system for the X-ray source and vacuum turbo pumps,
FG 500 - electron gun.

X-ray Photoelectron Spectroscopy (XPS), also referred to as Electron Spectroscopy for Chemical Analysis (ESCA), irradiates the sample surface with a soft (low energy) X-ray. This X-ray excites the electrons of the sample atoms and if their binding energy is lower than the X-ray energy, they will be emitted from the parent atom as a photoelectron. Only the photoelectrons at the extreme outer surface (10-100 Angstroms) can escape the sample surface, making this a surface analysis technique.

XPS analysis not only provides elemental information, but because the technique is detecting the binding energy of emitted electrons, it can also provide some chemical bonding information. Depending on what elements the parent atom is bound to, the binding energy of the emitted photoelectrons may shift slightly. The instrument is sensitive enough to detect these electron energy shifts and use them to determine what chemical compounds are present.

The XPS spectrometer is also equipped with an ion gun which allows depth profiling of the sample surface. This is extremly usefull in determining if contaminants are only present on the surface or reside in the sample bulk.