Untitled - IAP/TU Wien - Technische Universität Wien

Nanostructure Characterisation by Electron Beam Techniques
A R XPS - simulation and data analysis
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*corresponding author: s.oswald@ifw-dresden.de
Thin film technology developments require both reliable thin-layer and interface characterization. A
non-destructive method often used for depth-profile characterization in the nm thickness range is the
angle-resolved X-ray photoelectron spectroscopy (ARXPS). However, to extract the in-depth information
from such measurements in practice, dedicated mathematical models have to be applied. A further limitation
is that commonly the use of ARXPS is restricted away from the near-surface measuring angles due to effects
of elastic scattering on the measured intensities in this region. A further major point is the well-accepted
restriction that the information content of the ARXPS measurements should not be overvalued [1].
In this context the paper discusses the following topics:
(I) A procedure for computer simulation of reliable ARXPS data for complex near-surface structures
considering elastic scattering and analyzer acceptance [2,3]. This measurement simulation routine is based
on a Monte-Carlo simulation of electron paths in a small surface volume, which can be filled in principle
with any element distribution. (II) Demonstration of a modified common straight-line approximation based
EXCEL-routine for ARXPS data evaluation, which applies a simple empiric angle correction in the
high-angle region [4]. The two correction parameters, i.e. angle and strength, have to be determined from a
known thin film standard and can later on be implemented for similar unknown structures. (III) Examples for
multiple well-approximated solutions found for simulated ARXPS measurements at exactly-defined but more
complex surface structures. Here the necessity of the use of problem-specific boundary conditions is
underlined.
As a summary it is concluded that measurement simulation is a very useful tool for the estimation of
the limits of ARXPS interpretation and that the careful use of high-angle information can be helpful in the
case of special surface structures. Nevertheless the lack of information content cannot be overcome.
Partial funding of the work by DFG (Grant No. $!#7789:;7< is acknowledged.
References
[1] P.J. Cumpson, J. Electron Spectrosc. Rel. Phenom. 73 (1995) 25
[2] S. Oswald, F. Oswald, J. Appl. Phys. 100 (2006) 104504
[3] S. Oswald, F, Oswald, J. Appl. Phys. 109 (2011) 034305
[4] S. Oswald, F. Oswald, Surf. Interface Anal. 44 (2012) 1124#
40