Photoelectrons result from the interaction of electromagnetic
radiation
with matter. Useful energy range for the exciting
radiation is soft X-Ray
regime
in X-Ray Photoelectron Spectroscopy, XPS,
leading to core level
electrons excitation and hence to elemental selectivity. Excited
photo-
electrons are analyzed according to their
kinetic energy, which is, at
least for core
electrons, a fingerprint of the emitting element.
Elemental
identification is therefore possible (apart
from H and He) for core
level
photoemission. Elements' relative
abundance can in addition be made
semi-quantitative or quantitative.
Information on chemical bonds is derived either from core level
shifts.
Characteristic of the technique is its surface sensitivity (a
few monolayers),
which, combined with an etching process
(usually through sputtering by
accelerated noble ions) allows to measure elemental depth
distributions.
The most important feature is its ability to provide detailed
chemical
information on virtually any kind of solid sample, i.e. also
on insulating
or easily damaged samples. XPS
finds wide applications in several fields
of
science (surface physics, material science, geophysics,
nanomaterials,
biomaterials, polymers, organic
materials,....).
Specification of IOP XPS system:
System: VG system (operating since July 2001)
X-Ray Source: Dual anode MgKa and AlKa radiation
Analyzer:
Concentric Hemispherical Analyser (CHA)
with variable pass energy
Energy resolution: ~0.9eV
FWHM on Au4f7/2 with a pass energy of
20eV for XPS;
In-depth info.: Ar+ gun for deph profiling
Sample Stage: Tiltable
stage for angle dependent analysis
Can be resistivily heated to 8000C
Sensitivity:
0.5-1at%