ISO 13424:2013

INTERNATIONAL ISO
STANDARD 13424
First edition
2013-10-01
Surface chemical analysis — X-ray
photoelectron spectroscopy —
Reporting of results of thin-film analysis
Analyse chimique des surfaces — Spectroscopie de photoélectrons X
— Rapport des résultats de l’analyse de films minces
Reference number
©
ISO 2013
© ISO 2013
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ii © ISO 2013 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Overview of thin-film analysis by XPS . 1
5.1 Introduction . 1
5.2 General XPS . 3
5.3 Angle-resolved XPS . 3
5.4 Peak-shape analysis . 3
5.5 Variable photon energy XPS . 3
5.6 XPS with sputter-depth profiling . 3
6 Specimen handling . 4
7 Instrument and operating conditions . 4
7.1 Instrument calibration . 4
7.2 Operating conditions . 4
8 Reporting XPS method, experimental conditions, analysis parameters, and
analytical results . 5
8.1 XPS method for thin-film analysis . 5
8.2 Experimental conditions . 5
8.3 Analysis parameters . 6
8.4 Examples of summary tables . 7
8.5 Analytical Results. 9
Annex A (informative) General XPS .10
Annex B (informative) Angle-resolved XPS .18
Annex C (informative) Peak-shape analysis .24
Annex D (informative) XPS with sputter-depth profiling .37
Bibliography .40
Foreword
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The committee responsible for this document is ISO/TC 201, Surface chemical analysis, Subcommittee
SC 7, Electron spectroscopies.
iv © ISO 2013 – All rights reserved

Introduction
X-ray photoelectron spectroscopy (XPS) is widely used for the characterization of surfaces of materials,
especially for overlayer thin films on a substrate. The chemical composition of the near-surface region
of a thin film can be determined by XPS. If the film has a uniform thickness and the thickness is less than
about three times the mean escape depth (MED) for the measured photoelectrons, the film thickness and
the depth distribution of elements or chemical states of elements in the film can be determined by angle-
resolved XPS or peak-shape analysis . For thicker films, the depth distributions of elements in the film
can be obtained by sputter-depth profiling. Possible lateral inhomogeneities in film thicknesses or depth
profiles can be determined if the XPS system has sufficient lateral resolution. These XPS applications are
particularly valuable for characterizing thin-film nanostructures since the MED is typically less than
5 nm for many materials and common XPS measurement conditions.
Clauses 6 and 7 of this International Standard provide guidance to the operator of an XPS instrument in
making efficient measurements for determining meaningful chemical compositions and film thicknesses
for overlayer films on a substrate. Clause 8 of this International Standard shows the information to be
included in reports of the measurements and the analyses of the XPS data. Annex A, Annex B, Annex C,
and Annex D provide supplementary information on methods of data analysis for different types of XPS
measurements on thin-film samples.
INTERNATIONAL STANDARD ISO 13424:2013(E)
Surface chemical analysis — X-ray photoelectron
spectroscopy — Reporting of results of thin-film analysis
1 Scope
This International Standard specifies the minimum amount of information required in reports of
analyses of thin films on a substrate by XPS. These analyses involve measurement of the chemical
composition and thickness of homogeneous thin films, and measurement of the chemical composition
as a function of depth of inhomogeneous thin films by angle-resolved XPS, XPS sputter-depth profiling,
peak-shape analysis, and variable photon energy XPS.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 18115-1:2010, Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in
spectroscopy
3 Terms and definitions
For the purposes of this document, the terms and definitions in ISO 18115-1:2010 apply.
4 Abbreviated terms
AES Auger electron spectroscopy
ARXPS Angle-resolved X-ray photoelectron spectroscopy
IMFP Inelastic mean free path
MED Mean escape depth
RSF Relative sensitivity factor
TRMFP Transport mean free path
XPS X-ray photoelectron spectroscopy
5 Overview of thin-film analysis by XPS
5.1 Introduction
XPS analyses of thin films on substrate can provide information on the variation of chemical composition
with depth and on film thicknesses. Several XPS methods can be used if the total film thickness is less than
three times the largest MED for the detected photoelectrons. The MED for particular photoelectrons is
a function of the IMFP and the emission angle of the photoelectrons with respect to the surface normal.
The IMFP depends on the photoelectron energy and the material. MED values can be obtained from a
[1]
database. A simple analytical formula for estimating MEDs has been published for emission angles
[2]
≤50°. For such emission angles, the MED is less than the product of the IMFP and the cosine of the
emission angle by an amount that depends on the strength of the elastic scattering of the photoelectrons
[2]
in the film. Both the IMFP and the strength versus depend on the chemical composition of the film.
The MED is typically less than 5 nm for many materials and common XPS instruments and measurement
conditions. If the effects of elastic scattering are neglected, the MED is given approximately by the
product of the IMFP and the cosine of the emission angle. The latter estimates of the MED can be
sufficient for emission angles larger than 50° although better estimates can be obtained, e.g. from the
[1]
database. If the total film thickness is greater than three times the largest MED, XPS can be used under
certain conditions (see Annex D) together with ion sputtering to determine the variation of chemical
composition with depth.
Table 1 provides a summary of the XPS methods which can be used for determining chemical composition
and/or film thickness. Some methods can be utilized for the characterization of single-layer or multiple-
layer thin films on a substrate and some methods can be used to determine the composition-depth
profile of a sample for which the composition is a function of depth measured from the surface (i.e.
where there is not necessarily an interface between two or more phases). The choice of method typically
depends on the type of sample and the analyst’s knowledge of the likely or expected morphology of
the sample (i.e. whether the sample can consist of a single overlayer film on a flat substrate, multiple
films on a flat substrate, or a sample with composition varying continuously with depth), whether the
total film thickness is less than or greater than the largest MED for the detected photoelectrons, and
the desired information (i.e. film composition or film thickness). The first three methods in Table 1 are
non-destructive while the final method is destructive (i.e. the composi
...