Publications in Scientific Journals:
C.J. Powell, A. Jablonski, W.S.M. Werner, W. Smekal:
"Characterization of thin films on the nanometer scale by Augerelectron spectroscopy and X-ray photoelectron spectroscopy";
Applied Surface Science,
We describe two NIST databases that can be used to characterize thin films from Auger electron spectroscopy (AES) and Xray
photoelectron spectroscopy (XPS) measurements. First, the NIST Electron Effective-Attenuation-Length Database provides
values of effective attenuation lengths (EALs) for user-specified materials and measurement conditions. The EALs differ from
the corresponding inelastic mean free paths on account of elastic-scattering of the signal electrons. The database supplies
``practical’’ EALs that can be used to determine overlayer-film thicknesses. Practical EALs are plotted as a function of film
thickness, and an average value is shown for a user-selected thickness. The average practical EAL can be utilized as the ``lambda
parameter’’ to obtain film thicknesses from simple equations in which the effects of elastic-scattering are neglected. A single
average practical EAL can generally be employed for a useful range of film thicknesses and for electron emission angles of up to
about 608. For larger emission angles, the practical EAL should be found for the particular conditions. Second, we describe a
new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) to be released in 2004. This database
provides data for many parameters needed in quantitative AES and XPS (e.g., excitation cross-sections, electron-scattering
cross-sections, lineshapes, fluorescence yields, and backscattering factors). Relevant data for a user-specified experiment are
automatically retrieved by a small expert system. In addition, Auger electron and photoelectron spectra can be simulated for
layered samples. The simulated spectra, for layer compositions and thicknesses specified by the user, can be compared with
measured spectra. The layer compositions and thicknesses can then be adjusted to find maximum consistency between simulated
and measured spectra, and thus, provide more detailed characterizations of multilayer thin-film materials. SESSA can also
provide practical EALs, and we compare values provided by the NIST EAL database and SESSA for hafnium dioxide.
Differences of up to 10% were found for film thicknesses less than 20 A °
due to the use of different physical models in each
# 2004 Elsevier B.V. All rights reserved.
PACS: 68.55.Jk; 79.20.Ap; 79.20.Fv; 79.60. I; 82.80.Pv.
Keywords: Auger electron spectroscopy; AES; Databases; Film thicknesses; Quantitative analysis; Spectrum simulation; X-ray photoelectron
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