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<div align="center"><font size=5><b>Lunes 12 de noviembre - 13
hs<br><br>
</b>Aula de Seminarios del INQUIMAE, 3er piso Pab. II <br><br>
<br>
</font><font size=6><b>Michel J. Genet<br>
</font><font size=4><i>Unité de chimie des interfaces<br>
Université catholique de Louvain<br>
Louvain-la-Neuve (Belgium) <br><br>
<br>
</i></font><font size=5>"X-ray photoelectron spectroscopy: a
powerful tool applicable to all types of surfaces"<br><br>
</b></font></div>
Abstract:<br><br>
Most materials, but also living systems, are made of many constituents
between which are boundaries: surfaces and interfaces. There is a growing
interest in characterizing the surface of materials: atomic and molecular
composition, properties, organisation of their constituents in space.
This presentation will be focused on X-ray photoelectron spectroscopy
(XPS - ESCA). This technique, developed in the 1960's, is applicable to
all kinds of materials and in all research areas. The number of papers,
in which XPS is involved, continues to progress from year to
year.<br><br>
A survey of the principles of XPS as well as on the instrumentation will
be proposed, concomitantly with an overview of its qualitative and
quantitative potentialities. A sample, introduced in an ultra high vacuum
chamber, is irradiated with an X-ray beam. The kinetic energy 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 elemental sensitivity factors allow to
calculate elements concentrations with a detection limit of a few tenths
of mole percent. A detailed analysis of certain well-resolved peaks
allows quantifying the chemical functions present at the surface. On most
recent systems the lateral resolution is about 15 µm and 5 µm in
spectroscopic and imaging modes, respectively.<br><br>
Data interpretation will be illustrated by some recent results obtained
in very different areas: from steel corrosion to bio materials, from
minerals to food products.<br>
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