ISO 24639:2022

INTERNATIONAL ISO
STANDARD 24639
First edition
2022-07
Microbeam analysis — Analytical
electron microscopy — Calibration
procedure of energy scale for
elemental analysis by electron energy
loss spectroscopy
Analyse par microfaisceaux — Microscope électronique analytique
— Procédure d'étalonnage de l'échelle d'énergie pour l'analyse
élémentaire par spectroscopie de perte d'énergie des électrons
Reference number
ISO 24639:2022(E)
© ISO 2022

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ISO 24639:2022(E)
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© ISO 2022
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Published in Switzerland
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ISO 24639:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms.3
5 Energy calibration and its determination methods . 3
5.1 Equipment . 3
5.2 Calibration procedure for energy step and energy scale . 5
5.2.1 General . 5
5.2.2 Definition of peak positions . 6
5.2.3 Calibration for energy step . 7
5.2.4 Calibration for energy scale . . 9
5.2.5 Reference materials . 11
6 Test report .11
Annex A (informative) Calibration for the drift tube voltage in the magnetic prism .13
Annex B (informative) Estimation of linearity of the energy step .14
Bibliography .15
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ISO 24639:2022(E)
Foreword
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This document was prepared by Technical Committee ISO/TC 202, Microbeam analysis, Subcommittee
SC 3, Analytical electron microscopy.
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ISO 24639:2022(E)
Introduction
The electron energy loss spectroscopy (EELS) is an effective method for elemental analysis with
high spatial resolution. In a transmission electron microscope (TEM) or a scanning TEM (STEM),
incident electrons irradiating a sufficiently electron transparent sample, such as thin foil samples,
are scattered by the atoms in the sample. Inelastically scattered electrons are analysed to identify
elements in the sample by a spectrometer. All elements from hydrogen to uranium are identified based
upon comparisons of the peak energies and shapes of the core-loss edges, with table of peak energies
and spectra in handbooks for the different elements. To identify specific element core-loss peaks,
calibration of the EEL spectrometer to an uncertainty of ±3 % is generally adequate for energy range
0 eV to 3 000 eV. This document details the procedure for the energy calibration intended for work at
that level of accuracy.
Determination of a sample to be suitably electron transparent can be established by the EELS log ratio
technique (t/λ) for specimen thickness. For further details on the determination of relative specimen
thickness using the EELS log ratio technique (t/λ), see Reference [1].
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INTERNATIONAL STANDARD ISO 24639:2022(E)
Microbeam analysis — Analytical electron microscopy
— Calibration procedure of energy scale for elemental
analysis by electron energy loss spectroscopy
1 Scope
This document specifies a calibration procedure of the energy step and the energy scale for electron
energy loss spectroscopy in (scanning) transmission electron microscopes to an uncertainty of ±3 %
for the energy range 0 eV to 3 000 eV.
This document is intended for electron energy loss spectroscopy with transmitted electrons
through sufficiently electron transparent samples, such as a thin foil sample, and is not designed for
backscattered electrons from a bulk sample.
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 15932, Microbeam analysis — Analytical electron microscopy — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15932 and the following 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/
3.1
acceptance angle
γ
half of the angle formed by an entrance aperture to the EEL spectrometer
Note 1 to entry: See Figure 1.
3.2
channel
range of one pixel in the parallel detector (3.13)
3.3
collection angle
β
half of the angle formed by an objective aperture in a transmission electron microscope
Note 1 to entry: See Figure 1.
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ISO 24639:2022(E)
3.4
convergence angle
α
half of the angle of an electron beam focused by a condenser lens in a transmission electron microscope
Note 1 to entry: See Figure 1.
3.5
core-loss
energy loss of an electron in the beam caused by excitation of an inner shell electron
[SOURCE: ISO 15932:2013, 2.2.2.4]
3.6
core-loss edge onset
beginning position of a core-loss edge
Note 1 to entry: See Figure 3.
3.7
core-loss peak
peak maximum position of a core-loss edge
Note 1 to entry: See Figure 3.
3.8
EEL spectrometer
equipment of electrons energetically dispersed by electrostatic/electromagnetic elements and detected
by:
— direct electron detectors in serial detection (3.17),
— scintillator and a photomultiplier in serial detection (3.17),
— a scintillator and a photodiode array (3.14) in parallel detection, and
— optical lens coupled with scintillator and CCD/CMOS in parallel detection
3.9
elastically scattered electron
electron scattering in which energy and momentum are conserved in the collision system
[SOURCE: ISO 15932:2013, 2.2.1]
3.10
energy step
energy (eV) per one channel (3.2) in a spectrometer
3.11
in-column EEL spectrometer
EEL spectrometer (3.8) located in the imaging system of the TEM
3.12
inelastically scattered electron
electron scattering in which energy and/or momentum are not conserved in the collision system
Note 1 to entry: For inelastic scattering, the electron trajectory is modified by plasmon loss, core loss and other
multiple inelastic scatterings.
[SOURCE: ISO 15932:2013, 2.2.2]
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ISO 24639:2022(E)
3.13
parallel detector
simultaneous detector for energy-dispersed electrons using a photodiode array (3.14) or CCD or CMOS
Note 1 to entry: See Figure 1.
3.14
photodiode array
group connected by light tubes to the scintillator positioned at the energy dispersion plane, which
detects the energy of electrons simultaneously
3.15
plasmon-loss
type of energy loss in EEL in which the incident electron is affected by the collective oscillations of free
electrons in the specimen and loses kinetic energy as a result
[SOURCE: ISO 15932:2013, 2.2.2.2]
3.16
post-column EEL spectrometer
EEL spectrometer (3.8) located behind the imaging/detecting system of the TEM
3.17
serial detection
single channel detection in serial times along the energy axis
3.18
zero-loss
unscattered and elastically scattered electrons (3.9) (with only minimal loss of energy due to phonon
excitation), giving rise to an intensity peak or the position of which defines zero in the EEL spectrum
[SOURCE: ISO 15932:2013, 2.2.1.1]
4 Symbols and abbreviated terms
CCD charge coupled device
D measured energy step of the spectrometer, in eV / channel
dV change of voltage applied to the drift tube in the magnetic prism
EEL electron energy loss
EELS electron energy loss spectroscope/spectroscopy
Ei measured core-loss edges of the elements to be analysed, i, in eV
STEM scanning transmission electron microscope/spectroscopy
TEM transmission electron microscope/spectroscopy
Xi measured positions of zero-loss peak and core-loss edges, i, in channel
5 Energy calibration and its determination methods
5.1 Equipment
This document is intended for in-column EEL spectrometer, post-column EEL spectrometer and
alternative EEL spectrometer. EEL spectrometers basically work under the same principle as the post-
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ISO 24639:2022(E)
column EEL spectrometer. Since the post-column EEL spectrometer is widely used, it is adopted as the
typical EEL spectrometer. A serial detection system in the EEL spectrometer acquires a spectrum by
changing the energy in serial times, where the energy loss spectra are recorded sequentially. Since
serial times along the energy axis of serial detection can be replaced with multiple channels of p
...