ISO 17973:2024

International
Standard
ISO 17973
Third edition
Surface chemical analysis —
2024-07
Medium-resolution Auger electron
spectrometers — Calibration of
energy scales for elemental analysis
Analyse chimique des surfaces — Spectromètres d'électrons
Auger à résolution moyenne — Étalonnage des échelles d'énergie
pour l'analyse élémentaire
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 1
5 Outline of method . 2
6 Energy scale calibration procedures . 3
6.1 Obtaining reference samples .3
6.2 Mounting samples .3
6.3 Cleaning samples .3
6.4 Choosing spectrometer settings for energy calibration .5
6.5 Operating the instrument .5
6.6 Measurement of reference peaks .6
6.7 Determining measured kinetic energies of reference peaks .7
6.8 Determining correction of instrument kinetic energy scale .8
6.9 Next calibration .9
Bibliography .11

iii
Foreword
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The committee responsible for this document is Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 7, Electron spectroscopies.
This third edition cancels and replaces the second edition (ISO 17973:2016), which has been technically
revised.
The main changes are as follows:
— NOTE added to 6.3 to provide example sputtering conditions for cleaning sample surface;
— text added to 6.5 regarding need to check detector is operating within its linear region.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Auger electron spectroscopy (AES) is used extensively for the surface analysis of materials. Elements in the
sample (with the exception of hydrogen and helium) are identified from comparisons of the peak energies and
peak shapes, with tabulations of peak energies and data in handbooks of spectra for the different elements.
To identify the peaks, calibration of the energy scale with an uncertainty of 3 eV is generally adequate, and
this document is only intended for work at that level of accuracy (for greater accuracy, see ISO 17974).
The method for calibrating kinetic energy scales specified in this document uses metallic samples of pure
copper (Cu) and either aluminium (Al) or gold (Au). It does not include tests for defects in the instrument,
since few defects are significant at the level of accuracy concerned.
Traditionally, kinetic energies of Auger electrons have been referenced to the vacuum level, and this reference
is still used by many analysts. However, the vacuum level is ill-defined and can vary from instrument to
instrument over a range of 0,5 eV. Although use of the vacuum level reference procedure will generally not
cause ambiguity in elemental identification, it can cause uncertainty in measurements at high resolution
relating to chemical states. Because of this, instruments designed for both Auger electron spectroscopy and
X-ray photoelectron spectroscopy reference the kinetic energies to the Fermi level, giving values typically
4,5 eV higher than those referenced to the vacuum level. For the purposes of this document, the user is free
to choose the reference appropriate to their work.

v
International Standard ISO 17973:2024(en)
Surface chemical analysis — Medium-resolution Auger
electron spectrometers — Calibration of energy scales for
elemental analysis
1 Scope
This document specifies a method for calibrating the kinetic energy scales of Auger electron spectrometers
with an uncertainty of 3 eV, for general analytical use in identifying elements at surfaces. This document
also specifies a method for establishing a calibration schedule.
It is applicable to instruments used in either direct or differential mode, where the resolution is less than
or equal to 0,5 % and the modulation amplitude for the differential mode, if used, is 2 eV peak-to-peak. It is
applicable to those spectrometers equipped with an inert gas ion gun or other method for sample cleaning
and with an electron gun capable of operating at 4 keV or higher beam energy.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 18115 (all parts), Surface chemical analysis — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in the ISO 18115 series apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols and abbreviated terms
AES Auger electron spectroscopy
a measured energy scaling error
b measured zero offset error, in eV
E corrected result for kinetic energy corresponding to given E , in eV
corr meas
E measured kinetic energy, in eV
meas
E measured kinetic energy for peak n (see Table 1), in eV
meas,n
E reference values for kinetic energy position of peak n (see Table 1), in eV
ref,n
FWHM full width at half maximum peak intensity above background, in eV

W FWHM of peak
Δ offset energy, given by average measured kinetic energy for calibration peak minus reference
n
kinetic energy, in eV, for n = 1, 2, 3, 4 (see Table 1)
ΔE correction added to E after calibration to provide corrected kinetic energy result
corr meas
β energy scale scan rate for analogue systems, in eV/s
τ time constant for analogue detector electronics, in s
5 Outline of method
Calibration of an Auger electron spectrometer using this document is performed by obtaining and preparing
copper and gold or aluminium reference foils in order to measure the kinetic energies of selected Auger
electron peaks. These reference materials are chosen as they provide one Auger electron peak in the
high energy range, one in the middle range and one at low energies. The samples are cleaned and spectra
are recorded in the direct mode, if that is available, or in the differential mode if not. The energies of the
peaks are compared with reference values to provide an energy scale correction. How this correction is
implemented depends on the facilities available with the spectrometer. Because this calibration can alter
with time, a procedure is defined to enable the calibration to be established at regular intervals.
See Figure 1 for a flowchart showing the general structure of the work and the sequence of procedures.
NOTE The numbers refer to the corresponding subclauses in this document.
Figure 1 — Flowchart of method — Sequence of procedures

6 Energy scale calibration procedures
6.1 Obtaining reference samples
For the calibration of Auger electron spectrometers providing a high signal-to-noise ratio, as defined below,
and able to scan the kinetic energy range up to 2 100 eV, use samples of Cu and Au. For spectrometers with a
lower signal-to-noise ratio or those only able to scan to 2 000 eV, use samples of Cu and Al.
If, for the spectrometer used, the counts for the Cu L VV peak in the direct mode are less than 400 000 counts
per channel, or the root mean square noise in the differential spectrum exceeds 0,3 % of the Cu L VV peak-
to-peak signal, or if the maximum electron beam energy is less than 5 keV, Cu and Al may be used instead of
Cu and Au, since the recording of suitable Au data can be time consuming.
For instruments with higher signal intensities and for spectrometers able to scan to 2 100 eV, the use of Au
can be found to be the more convenient and able to provide a calibration over a wider energy range. The
requirement for 400 000 counts per channel for the Cu L VV peak may be relaxed to 100 000 counts per
[2]
channel if Savitzky and Golay smoothing is available at nine or more points in the smooth .
All samples shall be polycrystalline and of at least 99,8 % purity metals which, for convenience, are usually
in the form of foils typically of an area 10 mm by 10 mm, and from 0,1 mm to 0,2 mm thick.
If the samples appear to need cleaning, a short dip in 1 % nitric acid may be used for Cu with subsequent
rinsing in distilled water. If the Cu sample has been stored in the air for more than a few days, the dip in
nitric acid will make the sample cleaning (see 6.3) much easier.
NOTE Better signal-to-noise ratios are often obtained for 10 keV to 20 keV beam energies, rather than for lower
beam energies.
6.2 Mounting samples
Mount the samples of Cu and Au or Al on the sample holder or on separate sample holders, as appropriate,
using fixing screws or other metallic means to ensure electrical contact. Double-sided adhesive tape shall
not be used.
6.3 Cleaning samples
Achieve ultra-high vacuum and clean the samples by ion sputtering to reduce the contamination until the
heights of the oxygen and carbon Auger electron peaks are each less than 2 % of the height of the most
intense metal peak in each survey spectrum. Record a survey (wide scan) spectrum for each of the samples
to ensure that the only significant peaks are those of the required pure elements. The quality of vacuum
necessary here is such that the oxygen and carbon peak heights shall not exceed 3 % of the heights of the
most intense metal peaks by the completion of the procedure in accordance with 6.6 or at the end of the
working day, whichever is the earlier.
All relevant procedures of this International Standard should be completed in one working day. If more than
one day is required, the cleanness of the samples shall be confirmed at the start of each day's work.
NOTE Inert gas ion sputtering conditions that have been found suitable for cleaning are 1 min of a 30 μA beam of
5 keV argon ions covering 1 cm of the sample.
For examples of direct and differential spectra, see Figure 2.

ISO 17973:
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