Chemistry Reference
In-Depth Information
spectrum. The fiber IRE for in situ studies of organic thin film deposition/etching in
reactive nonthermal plasmas was realized by guiding the fiber through the plasma
reactor and removing the polyamide protection layer from a part of the fiber in the
plasma zone [22,26].
7.2 X-RAY PHOTOELECTRON SPECTROSCOPY (XPS)
7.2.1 E
XPERIMENTAL
S
ETUP
XPS is the most widely used surface analysis technique for plasma-modified surfaces
and plasma-enhanced deposited thin films. Especially, biomaterial surface modifi-
cation pushed the advancement of devices and techniques [27,28]. The XPS, also
known as ESCA (electron spectroscopy for chemical analysis) determines surface
elemental compositions, its molecular state, unpaired electrons, organic groups, sur-
face heterogeneity, lateral surface variation, and allows the identification of specific
valence bands [29].
Performing an XPS measurement, a sample is irradiated with soft x-rays. In most
cases, Mg Kα (1 253.6 eV) or Al Kα (1 486.6 eV) x-rays are used (see Figure 7.10
with a schematic view of an XPS device and photoelectric process for 1s electron
emission). The x-ray photons interact with the atoms in the surface region causing
core electrons to be emitted by the photoelectric effect. The energy and the amount
of the emitted electrons are analyzed. The measured kinetic energy of the electrons
is given by
E
k
=
h
ν
−
E
b
−
φ,
(7.19)
where
h
ν is the energy of the photons
E
b
is the binding energy of the atomic orbital the electron originates from
φ is the spectrometer work function
HSA
Amplifier
detector
Transfer
system
X-ray
gun
L
23
or 2p
L
1
or 2s
X-ray
photon
Photo
electron
K or 1s
FIGURE 7.10
Schematic view of an XPS device and photoelectric process for 1s electron
emission. HSA, hemispherical energy analyzer.
