ISO 17973:2016
(Main)Surface chemical analysis — Medium-resolution Auger electron spectrometers — Calibration of energy scales for elemental analysis
Surface chemical analysis — Medium-resolution Auger electron spectrometers — Calibration of energy scales for elemental analysis
ISO 17973:2016 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. In addition, it 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.
Analyse chimique des surfaces — Spectromètres d'électrons Auger à résolution moyenne — Étalonnage des échelles d'énergie pour l'analyse élémentaire
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FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 17973
ISO/TC 201/SC 7
Surface chemical analysis —
Secretariat: BSI
Medium-resolution Auger electron
Voting begins on:
201605-16 spectrometers — Calibration of
energy scales for elemental analysis
Voting terminates on:
201607-11
Analyse chimique des surfaces — Spectromètres d’électrons Auger
à résolution moyenne — Étalonnage des échelles d’énergie pour
l’analyse élémentaire
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/FDIS 17973:2016(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN
DARDS TO WHICH REFERENCE MAY BE MADE IN
©
NATIONAL REGULATIONS. ISO 2016
ISO/FDIS 17973:2016(E)
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
ISO/FDIS 17973:2016(E)
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
ISO/FDIS 17973:2016(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and nongovernmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 201, Surface chemical analysis, Subcommittee
SC 7, Electron spectroscopies.
This second edition cancels and replaces the first edition (ISO 17973:2002), of which it constitutes a
minor revision, which includes changing “counts per second” to “counts per channel”.
iv © ISO 2016 – All rights reserved
ISO/FDIS 17973:2016(E)
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 International Standard 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 International Standard 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 may 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 International Standard, the user is free to choose the reference appropriate to his
or her work.
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 17973:2016(E)
Surface chemical analysis — Medium-resolution Auger
electron spectrometers — Calibration of energy scales for
elemental analysis
1 Scope
This International Standard 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. In addition, it 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 peaktopeak. 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, 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 (all parts), Surface chemical analysis — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115 apply.
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 refer
n
ence kinetic energy, in eV, for n = 1, 2, 3, 4 (see Table 1)
ISO/FDIS 17973:2016(E)
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 International Standard 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 may 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 International Standard.
Figure 1 — Flowchart of method — Sequence of procedures
2 © ISO 2016 – All rights reserved
ISO/FDIS 17973:2016(E)
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 may be time consuming.
For instruments with higher signal intensities and for spectrometers able to scan to 2 100 eV, the use
of Au could 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
[2]
counts per 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 signaltonoise ratios are often obtained for 10 keV to 20 keV beam energies, rather than for
lower beam energies.
6.2 Mounting samples
Mount
...
INTERNATIONAL ISO
STANDARD 17973
Second edition
2016-09-01
Surface chemical analysis —
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 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is Technical Committee ISO/TC 201, Surface chemical
analysis, Subcommittee SC 7, Electron spectroscopies.
This second edition cancels and replaces the first edition (ISO 17973:2002), of which it constitutes a
minor revision, which includes changing “counts per second” to “counts per channel”.
iv © ISO 2016 – All rights reserved
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 International Standard 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 International Standard 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 may 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 International Standard, the user is free to choose the reference appropriate to his
or her work.
INTERNATIONAL STANDARD ISO 17973:2016(E)
Surface chemical analysis — Medium-resolution Auger
electron spectrometers — Calibration of energy scales for
elemental analysis
1 Scope
This International Standard 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. In addition, it 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, 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 (all parts), Surface chemical analysis — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115 apply.
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 refer-
n
ence 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 International Standard 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 may 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 International Standard.
Figure 1 — Flowchart of method — Sequence of procedures
2 © ISO 2016 – All rights reserved
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 may be time consuming.
For instruments with higher signal intensities and for spectrometers able to scan to 2 100 eV, the use
of Au could 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
[2]
counts per 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
...
INTERNATIONAL ISO
STANDARD 17973
Second edition
2016-09-01
Surface chemical analysis —
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 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the
Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is Technical Committee ISO/TC 201, Surface chemical
analysis, Subcommittee SC 7, Electron spectroscopies.
This second edition cancels and replaces the first edition (ISO 17973:2002), of which it constitutes a
minor revision, which includes changing “counts per second” to “counts per channel”.
iv © ISO 2016 – All rights reserved
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 International Standard 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 International Standard 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 may 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 International Standard, the user is free to choose the reference appropriate to his
or her work.
INTERNATIONAL STANDARD ISO 17973:2016(E)
Surface chemical analysis — Medium-resolution Auger
electron spectrometers — Calibration of energy scales for
elemental analysis
1 Scope
This International Standard 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. In addition, it 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, 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 (all parts), Surface chemical analysis — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 18115 apply.
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 refer-
n
ence 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 International Standard 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 may 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 International Standard.
Figure 1 — Flowchart of method — Sequence of procedures
2 © ISO 2016 – All rights reserved
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 may be time consuming.
For instruments with higher signal intensities and for spectrometers able to scan to 2 100 eV, the use
of Au could 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
[2]
counts per 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
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