X-ray photoelectron spectroscopy
Principles
X-ray photoelectron spectroscopy (XPS - ESCA) was developed in the mid 1960s by the K. Siegbahn group (University of Uppsalla, Sweden). The first Belgian XPS system was installed in our laboratory beginning 1970s. A sample, introduced in an ultra high vacuum chamber, is bombarded with an X-ray beam. The kinetic energy (in electron volts, eV) of emitted electrons of all elements (except H and He) present at the surface (analyzed depth between 1 and 10 nm) is measured with a precision of about 0.2 eV. Shape and position of peaks depend on the chemical state of the element (the so-called " chemical shift " effect). Area of peaks used in combination with sensitivity factors allow to calculate mole fractions with a detection limit of a few tenths of percent. A detailed analysis of certain well-resolved peaks allows quantifying functionalities present at the surface. On most recent systems the minimum spatial resolution is of about 15 碌m and 5 碌m for XPS analysis and XPS imaging respectively. In most cases XPS can be considered as a non-destructive technique.
Applications
XPS can be used to characterize the surface of all types of materials, quite exclusively solids (powders or bulk specimen): biomaterials, catalysts, ceramics, fibers, glass, metals, minerals, polymers... The laboratories sharing the XPS facilities of the Surface Characterisation platform have an uncommon expertise in using the method.
Systems
SSX 100/206 spectrometer from Surface Science Instruments (USA): monochromatized and microfocused AlK伪听X-ray beam, parking chamber, automatic sample analysis.
Kratos Axis Ultra spectrometer from Kratos Analytical (UK): monochromatized AlK伪听听听X-ray beam, Al/Mg non monochromatized twin anode, XPS imaging, catalyst cell (maximum 800掳C), sample cooling (~160掳C) in both introduction and analysis chamber, ion gun, parking chamber, automatic sample analysis.
Access
Our XPS systems are accessible to academic and industrial research teams. For more information please contact听Pierre Eloy听
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Useful links
UK ESCA Users Group Surface Science Site ()
Surface Science Network ()
NIST听Standard Reference Data Product Catalog ()