ISO 18115-1:2023

ISO TC 201/SC 1
Date: 2022-12-122023-02-17
ISO/FDIS 18115-1:XXXX2023(E)
ISO TC 201/SC 1
Secretariat: ANSI
Surface chemical analysis — Vocabulary — Part 1: General terms and terms used in
spectroscopy
Analyse chimique des surfaces — Vocabulaire — Partie 1: Termes généraux et termes utilisés en
spectroscopie

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ISO/FDIS 18115-1:2023(E)
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ii © ISO 2023 – All rights reserved

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ISO/FDIS 18115-1:2023(E)
Contents
Foreword . iv_Toc127783246
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms related to general concepts in surface chemical analysis . 1
4 Terms related to particle transport in materials . 12
5 Terms related to the description of samples . 21
6 Terms related to sample preparation . 24
7 Terms related to instrumentation. 25
8 Terms related to experimental conditions . 29
9 Terms related to sputter depth profiling . 38
10 Terms related to resolution . 42
11 Terms related to electron spectroscopy methods . 47
12 Terms related to electron spectroscopy analysis . 50
13 Terms related to X-ray fluorescence, reflection and scattering methods . 70
14 Terms related to X-ray fluorescence, reflection and scattering analysis . 73
15 Terms related to glow discharge methods . 74
16 Terms related to glow discharge analysis . 75
17 Terms related to ion scattering methods. 83
18 Terms related to ion scattering analysis . 85
19 Terms related to surface mass spectrometry methods . 88
20 Terms related to surface mass spectrometry analysis . 93
21 Terms related to atom probe tomography . 101
22 Terms related to multivariate analysis . 104
Bibliography . 114
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ISO/FDIS 18115-1:2023(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 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 of the voluntary nature of standards, 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
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 1, Terminology.
This third edition cancels and replaces the second edition (ISO 18115-1:2013), which has been
technically revised in this edition.
The main changes are as follows:
— Revisionrevision of definitions related to resolution;
— Introductionintroduction of definitions related to atom probe tomography;
— Introductionintroduction of emerging methods such as HAXPES, NAPXPS, GEXRF;
— Removalremoval of repeated or redundant definitions and references;
— Reorganisationreorganisation of the terminology into subject-specific sections;
— Removalremoval of Annexes according to ISO requirements.
A list of all parts in the ISO 18115 series can be found on the ISO website.
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.
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ISO/FDIS 18115-1:2023(E)
Introduction
Surface chemical analysis is an important area which involves interactions between people with
different backgrounds and from different fields. Those conducting surface chemical analysis can be
materials scientists, chemists, or physicists and can have a background that is primarily experimental or
primarily theoretical. Those making use of the surface chemical data extend beyond this group into
other disciplines.
With the present techniques of surface chemical analysis, compositional information is obtained for
regions close to a surface (generally within 20 nm) and composition-versus-depth information is
obtained with surface analytical techniques as surface layers are removed. The surface analytical terms
covered in this document extend from the techniques of electron spectroscopy and mass spectrometry
to optical spectrometry and X-ray analysis. The terms covered in ISO 18115-2 relate to scanning-probe
microscopy. The terms covered in ISO 18115-3 relate to optical interface analysis. Concepts for these
techniques derive from disciplines as widely ranging as nuclear physics and radiation science to
physical chemistry and optics.
The wide range of disciplines and the individualities of national usages have led to different meanings
being attributed to particular terms and, again, different terms being used to describe the same concept.
To avoid the consequent misunderstandings and to facilitate the exchange of information, it is essential
to clarify the concepts, to establish the correct terms for use, and to establish their definitions.
The terms are classified under Clauses 3 to 22:
— Clause 3: Terms related to general concepts in surface chemical analysis;
— Clause 4: Terms related to particle transport in materials;
— Clause 5: Terms related to the description of samples;
— Clause 6: Terms related to sample preparation;
— Clause 7: Terms related to instrumentation;
— Clause 8: Terms related to experimental conditions;
— Clause 9: Terms related to sputter depth profiling;
— Clause 10: Terms related to resolution;
— Clause 11: Terms related to electron spectroscopy methods;
— Clause 12: Terms related to electron spectroscopy analysis;
— Clause 13: Terms related to X-ray fluorescence, reflection and scattering methods;
— Clause 14: Terms related to X-ray fluorescence, reflection and scattering analysis;
— Clause 15: Terms related to glow discharge methods;
— Clause 16: Terms related to glow discharge analysis;
— Clause 17: Terms related to ion scattering methods;
— Clause 18: Terms related to ion scattering analysis;
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ISO/FDIS 18115-1:2023(E)
— Clause 19: Terms related to surface mass spectrometry methods;
— Clause 20: Terms related to surface mass spectrometry analysis;
— Clause 21: Terms related to atom probe tomography;
— Clause 22: Terms related to multivariate analysis.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 18115-1:2023(E)

Surface chemical analysis — Vocabulary — Part 1: General terms
and terms used in spectroscopy
1 Scope
This part of the ISO 18115 series defines terms for surface chemical analysis. It covers general terms
and those used in spectroscopy, while ISO 18115-2 covers terms used in scanning-probe microscopy
and ISO 18115-3 covers terms used in optical interface analysis.
2 Normative references
There are no normative references in this document.
3 Terms related to general concepts in surface chemical analysis
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
interface
boundary between two phases having different chemical, elemental, or physical properties
3.2
surface
interface (3.1) between a condensed phase and a gas, vapour, or free space
3.3
measurand
quantity intended to be measured
[ [1] ]
[SOURCE: ISO/IEC Guide 99:2007 , , 2.3, modified — The notes to entry have been deleted.]
3.4
analyte
substance or chemical constituent that is subjected to measurement
3.5
chemical species
atom, molecule, ion, or functional group
3.6
unified atomic mass unit
u
dalton
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ISO/FDIS 18115-1:2023(E)
Da
12
unit equal to 1/12 of the mass of the nuclide C at rest and in its ground state
−27
Note 1 to entry: 1 u ≈ 1,660 538 86 × 10 kg with a one-standard-deviation uncertainty of ±0,000 000
−27 [ [2] ]
28 × 10 kg . . This is a non-SI unit, accepted for use with the International System, whose value in SI units is
obtained experimentally.
Note 2 to entry: The term dalton, symbol Da, is preferred over unified atomic mass unit as it is both shorter and
works better with prefixes.
Note 3 to entry: The above definition was agreed upon by the International Union of Pure and Applied Physics in
1960 and the International Union of Pure and Applied Chemistry in 1961, resolving a longstanding difference
between chemists and physicists. The unified atomic mass unit replaced the atomic mass unit (chemical scale) and
the atomic mass unit (physical scale), both having the symbol amu. The amu (physical scale) was one-sixteenth of
the mass of an atom of oxygen-16. The amu (chemical scale) was one-sixteenth of the average mass of oxygen
atoms as found in nature. In the 1998 CODATA, 1 u = 1,000 317 9 amu (physical scale) = 1,000 043 amu (chemical
scale).
3.7
reference method
thoroughly investigated method, clearly and exactly describing the necessary conditions and
procedures for the measurement of one or more property values, that has been shown to have accuracy
and precision commensurate with its intended use and that can therefore be used to assess the
accuracy of other methods for the same measurement, particularly in permitting the characterization of
a reference material (5.1)
[3]
[SOURCE: ISO Guide 30:1992+A1:2008 ]
3.8
quantitative analysis
determination of the amount of analyte (3.4) detected in, or on, a sample
Note 1 to entry: The analytes can be elemental or compound in nature.
Note 2 to entry: The amounts can be expressed, for example, as atomic or mass percent, atomic or mass fraction,
mole or mass per unit volume, as appropriate or as desired.
Note 3 to entry: The sample material can be inhomogeneous so that a particular model structure may be assumed
in the interpretation. Details of that model should be stated.
3.9
detection limit
smallest amount of an element or compound that can be measured under specified analysis conditions
Note 1 to entry: The detection limit is often taken to correspond to the amount of material for which the total
signal for that material minus the background signal (3.21) is three times the standard deviation of the signal
above the background signal. This approach is simplistic and, for more accurate and rigorous definitions of
detection limits, the References [4] and [5] should be consulted.
Note 2 to entry: The detection limit can be expressed in many ways, depending on the purpose. Examples of ways
of expressing it are mass or weight fraction, atomic fraction, concentration, number of atoms, and mass or weight.
Note 3 to entry: The detection limit is generally different for different materials.
3.10
matrix effects
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ISO/FDIS 18115-1:2023(E)
change in the intensities or spectral information per atom of the analyte (3.4) arising from change in the
chemical or physical environment
Note 1 to entry: Examples of these environments are varying sample morphologies [e.g. thin films (5.13), clusters,
fibres, nanostructures] of different dimensions, the amorphous or crystalline state, changes of matrix species, and
the proximity of other physical phases or chemical species (3.5).
3.11
matrix factor
factors, arising from the composition of the matrix, for multiplying the quotient of the measured
intensity and the appropriate sensitivity factor in formulae to determine the composition using surface
analytical techniques
Note 1 to entry: See average matrix sensitivity factor and pure-element sensitivity factor.
Note 2 to entry: In methods such as AES (11.1), the matrix factor is determined in part by the composition of the
sub-surface material and in part by the composition of the analysis volume (8.48) in the sample.
3.12
absolute elemental sensitivity factor
coefficient for an element by which the measured intensity for that element is divided to yield the
atomic concentration or atomic fraction of the element present in the sample
Note 1 to entry: See elemental relative sensitivity factor (12.92) (20.61).
Note 2 to entry: The choice of atomic concentration or atomic fraction should be made clear.
Note 3 to entry: The type of sensitivity factor utilized should be appropriate for the formulae used in the
quantification process and for the type of sample analysed, for example homogeneous samples or segregated
layers.
Note 4 to entry: The source of sensitivity factors should be given to ensure that the correct matrix factors (3.11) or
other parameters are used.
Note 5 to entry: Sensitivity factors depend on parameters of the excitation source, the spectrometer, and the
orientation of the sample to these parts of the instrument. Sensitivity factors also depend on the matrix being
analysed, and in SIMS (19.1) this has a dominating influence.
3.13
step size
distance between values in measurand (3.3) space from which individual data points are acquired
3.14
sweep
single, complete acquisition of one set of data
3.15
peak intensity
measure of signal intensity (3.17) for a constituent spectral peak
Note 1 to entry: Intensity is usually measured for quantitative purposes which can be the height of the peak above
a defined background or the peak area (3.16). The units can be counts (3.18), counts⋅electron volts, counts per
second, counts⋅electron volts per second, counts per amu, counts per second per amu, etc. For differential spectra,
the intensity can be the peak-to-peak height or the peak-to-background height. The measure of intensity should be
defined and the units stated in each case.
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ISO/FDIS 18115-1:2023(E)
Note 2 to entry: The meaning is very rarely the literal meaning of the intensity value at the top of the measured
peak either before or after removal of any background.
3.16
peak area
area under a peak in a spectrum after background removal
Note 1 to entry: See inelastic electron scattering background subtraction (12.85) and signal intensity (3.17).
Note 2 to entry: The peak area can be expressed in counts (3.18), counts per second, counts⋅electron volts,
counts⋅electron volts per second, counts per amu, or other units.
3.17
signal intensity
strength of a measured signal at a spectrometer detector or after some defined processing
Note 1 to entry: The signal intensity is subject to significant change between the points of generation and
detection of the signal and, further, between the points of detection and display on the measuring instrument.
Note 2 to entry: The signal intensity can be expressed in counts (3.18) (per channel) or counts per second (per
channel) or counts⋅electron volts per second or other units. In AES (11.1), the differential of the signal intensity
may be obtained by analogue modulation (12.61) of an electrode in the spectrometer or by numerical
differentiation of the spectrum. The type of signal shall be defined.
Note 3 to entry: In an electron or mass spectrum (20.58), the measured spectrum integrated over energy or mass
and solid angle is equal to a current. If the spectrometer has been calibrated, the units of intensity can be
−1 −1 −1 −1
current⋅eV ⋅sr or current⋅amu ⋅sr . If the spectrum has been normalized to unit primary-beam (4.808.10)
−1 −1 −1 −1
current, the appropriate units would be eV ⋅sr or amu ⋅sr . If the spectrum has also been integrated over the
−1 −1
emission solid angle, the appropriate units would be eV or amu .
3.18
counts
total number of pulses recorded by a detector system in a defined time interval
Note 1 to entry: The counts can be representative, one-for-one with the particles being detected [in the absence of
dead time (7.17) losses in the counting measurement] in which case they follow Poissonian statistics [unless other
noise (3.19) sources are present] or they can simply be proportional to the number of particles being detected.
The type of measure shall be clearly stated.
Note 2 to entry: In multidetector systems, the apportion of counts into relevant channels of the spectrum can lead
to changes from the expected Poissonian statistics in each channel since the counts in neighbouring channels can
be partly correlated.
3.19
noise
time-varying disturbances superimposed on the analytical signal with fluctuations, leading to
uncertainty in the signal intensity (3.17)
Note 1 to entry: An accurate measure of noise can be determined from the standard deviation of the fluctuations.
Visual or other estimates, such as peak-to-peak noise in a spectrum, can be useful as semiquantitative measures of
noise.
Note 2 to entry: The fluctuations in the measured intensity can arise from a number of causes, such as statistical
noise (3.20) and electrical interference.
3.20
statistical noise
noise (3.19) in the spectrum due solely to the statistics of randomly detected single events
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ISO/FDIS 18115-1:2023(E)
Note 1 to entry: For single-particle counting systems exhibiting Poisson statistics, the standard deviation of a large
number of measures of an otherwise steady count rate, N, each in the same time interval, is equal to the square
root of N.
Note 2 to entry: In multidetector systems, the data processing required to generate the output spectrum can lead
to statistical correlation between adjacent channels and also an apparent noise in each channel that is less than
Poissonian.
3.21
background signal
signal present at a particular position, energy, mass or wavelength due to processes or sources other
than those of primary interest
Note 1 to entry: See metastable background (20.36), Shirley background (12.86), Sickafus background (12.87), and
Tougaard background (12.88).
3.22
peak-to-background ratio
signal-to-background ratio
ratio of the maximum height of the peak above the background intensity to the magnitude of that
background intensity
Note 1 to entry: Signal-to-background ratio is the more commonly used term in GDS (15.1), where it is
abbreviated to SBR. Peak-to-background ratio is the more commonly used term for types of electron
spectroscopies such as AES (11.1) and XPS (11.6).
Note 2 to entry: The method of estimating the background intensity shall be given. For AES, the background
intensity is often determined at a kinetic energy (3.35) just above the peak of interest.
3.23
signal-to-noise ratio
ratio of the signal intensity (3.17) to a measure of the total noise (3.19) in determining that signal
Note 1 to entry: See statistical noise (3.20).
Note 2 to entry: The noise in AES (11.1) is often measured at a convenient region of the spectral background close
to the peak.
3.24
smoothing
mathematical treatment of data to reduce the apparent noise (3.19)
3.25
interference signal
signal, measured at the mass, energy, or wavelength position of
interest, due to another, undesired, species
Note 1 to entry: In general laboratory use, interference can be used more broadly to indicate electrical noise
(3.19), line pick-up, or other unwanted contributions to the detected signal.
3.26
relative standard deviation of the background
quotient of the standard deviation characterizing the noise (3.19) in the background signal (3.21) by the
intensity of the background signal
3.27
lineshape
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ISO/FDIS 18115-1:2023(E)
measured shape of a particular spectral feature
3.28
peak width
width of a peak at a defined fraction of the peak height
Note 1 to entry: See intrinsic linewidth (12.22).
Note 2 to entry: Any background subtraction method used should be specified.
Note 3 to entry: The most common measure of peak width is the full width of the peak at half maximum (FWHM)
intensity.
Note 4 to entry: For asymmetrical peaks, convenient measures of peak width are the half-widths of each side of
the peak at half maximum intensity.
3.29
peak fitting
procedure whereby a spectrum, generated by peak synthesis (3.30), is adjusted to match a measured
spectrum
Note 1 to entry: A least-squares optimization procedure is generally used in a computer programme for this
purpose.
Note 2 to entry: The selected peak shape and the background shape should be defined. Any constraints imposed
on the adjustment process should also be defined.
3.30
peak synthesis
procedure whereby a synthetic spectrum is generated, using either model or experimental peak shapes,
in which the number of peaks, the peak shapes, the peak widths (3.28), the peak positions, the peak
intensities, and the background shape and intensity are adjusted for peak fitting (3.29)
Note 1 to entry: The selected peak shape and the background shape should be defined.
3.31
lateral profile
chemical or elemental composition, signal intensity (3.17) or processed intensity information from the
available software measured in a specified direction parallel to the surface (3.2)
Note 1 to entry: See line scan (8.56).
3.32
depth profile
vertical profile
chemical or elemental composition, signal intensity (3.17) or processed intensity information from the
available software measured in a direction normal to the surface (3.2)
Note 1 to entry: See compositional depth profile (3.33).
3.33
compositional depth profile
CDP
atomic or molecular composition measured as a function of distance normal to the surface (3.2)
3.34
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ISO/FDIS 18115-1:2023(E)
depth profiling
monitoring of signal intensity (3.17) as a function of a variable that can be related to distance normal to
the surface (3.2)
Note 1 to entry: See compositional depth profile (3.33).
Note 2 to entry: In a sputter depth profile (9.1) the signal intensity is usually measured as a function of the
sputtering (9.3) time.
3.35
kinetic energy
energy of motion
Note 1 to entry: The energy of a charged particle due to motion is not necessarily constant and varies with the
local electric potential. If all local electrodes are at ground potential, the kinetic energy of the particle varies with
the local vacuum level (12.10). This vacuum level can vary over a range of 1 eV in different regions of AES (11.1)
and XPS (11.6) instruments and measured electron energies can similarly vary. This variation is removed if the
kinetic energies are referred to the Fermi level (12.9). In XPS, by convention, the Fermi level is always used but in
AES both vacuum (12.76) and Fermi level referencing (12.75) are practised. Instruments capable of both AES and
XPS are Fermi level referenced. Fermi level referencing is recommended for accurate measurements of energies in
AES. In electron spectrometers (12.58), Fermi level referenced energies are typically 4,5 eV greater than those
referenced to the vacuum level. It is convenient in AES to assume a standard vacuum level (12.11) of 4,500 eV
above the Fermi level so that the energies of Auger electron (12.32) peaks, referenced to the Fermi level, can be
converted in a consistent way to energies referenced to the vacuum level and vice versa.
3.36
ion species
type and charge of an ion
+ − +
EXAMPLES Ar , O , and H2 .
Note 1 to entry: If an isotope is used, it should be specified.
3.37
radical
atoms or molecular entity possessing an unpaired electron
• • •
Note 1 to entry: Entities such as CH3, SnH3, and Cl have formulae in which the dot symbolizing the unpaired
electron is placed so as to indicate the atom of highest spin density, if this is possible. Paramagnetic metal ions are
not normally regarded as radicals.
Note 2 to entry: Depending upon the core atom that possesses the unpaired electron, the radicals can be described
as carbon-, oxygen-, nitrogen-, or metal-centred radicals. If the unpaired electron occupies an orbital having
considerable “s” or more or less pure “p” character, the respective radicals are termed σ- or π-radicals.
Note 3 to entry: The adjective “free” is no longer used.
3.38
radical ion
radical (3.37) carrying an electric charge
•+
Note 1 to entry: A positively charged radical is called a “radical cation” (e.g. the benzene radical cation C H ); a
6 6
•−
negatively charged radical is called a “radical anion” (e.g. the benzene radical anion C H or the benzophenone
6 6
•−
radical anion Ph2C−O ). Commonly, but not necessarily, the odd electron and the charge are associated with the
same atom. Unless the positions of unpaired spin and charge can be associated with specific atoms, superscript
dot and charge designations should be placed in the order •+ or •− as suggested by the name “radical ion” (e.g.
•+
C H ).
3 6
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ISO/FDIS 18115-1:2023(E)
3.39
light ion
ion lighter than lithium
Note 1 to entry: See intermediate-mass ion (3.40) and heavy ion (3.41).
3.40
int
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 18115-1
ISO/TC 201/SC 1
Surface chemical analysis —
Secretariat: ANSI
Vocabulary —
Voting begins on:
2023-03-06
Part 1:
Voting terminates on:
General terms and terms used in
2023-05-01
spectroscopy
Analyse chimique des surfaces — Vocabulaire —
Partie 1: Termes généraux et termes utilisés en spectroscopie
RECIPIENTS OF THIS DRAFT ARE INVITED TO
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BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 18115-1:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
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NATIONAL REGULATIONS. © ISO 2023

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ISO/FDIS 18115-1:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 18115-1
ISO/TC 201/SC 1
Surface chemical analysis —
Secretariat: ANSI
Vocabulary —
Voting begins on:
Part 1:
Voting terminates on:
General terms and terms used in
spectroscopy
Analyse chimique des surfaces — Vocabulaire —
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ISO/FDIS 18115-1:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms related to general concepts in surface chemical analysis .1
4 Terms related to particle transport in materials .11
5 Terms related to the description of samples .20
6 Terms related to sample preparation .23
7 Terms related to instrumentation .24
8 Terms related to experimental conditions .27
9 Terms related to sputter depth profiling .36
10 Terms related to resolution .40
11 Terms related to electron spectroscopy methods .45
12 Terms related to electron spectroscopy analysis .48
13 Terms related to X-ray fluorescence, reflection and scattering methods .66
14 Terms related to X-ray fluorescence, reflection and scattering analysis .69
15 Terms related to glow discharge methods .70
16 Terms related to glow discharge analysis .70
17 Terms related to ion scattering methods .78
18 Terms related to ion scattering analysis .80
19 Terms related to surface mass spectrometry methods .84
20 Terms related to surface mass spectrometry analysis .87
21 Terms related to atom probe tomography .95
22 Terms related to multivariate analysis .98
Bibliography . 107
Index . 108
iii
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ISO/FDIS 18115-1:2023(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 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 of the voluntary nature of standards, 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
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 1, Terminology.
This third edition cancels and replaces the second edition (ISO 18115-1:2013), which has been
technically revised.
The main changes are as follows:
— revision of definitions related to resolution
— introduction of definitions related to atom probe tomography
— introduction of emerging methods such as HAXPES, NAPXPS, GEXRF
— removal of repeated or redundant definitions and references
— reorganisation of the terminology into subject-specific sections
— removal of Annexes according to ISO requirements
A list of all parts in the ISO 18115 series can be found on the ISO website.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.
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ISO/FDIS 18115-1:2023(E)
Introduction
Surface chemical analysis is an important area which involves interactions between people with
different backgrounds and from different fields. Those conducting surface chemical analysis can be
materials scientists, chemists, or physicists and can have a background that is primarily experimental
or primarily theoretical. Those making use of the surface chemical data extend beyond this group into
other disciplines.
With the present techniques of surface chemical analysis, compositional information is obtained for
regions close to a surface (generally within 20 nm) and composition-versus-depth information is
obtained with surface analytical techniques as surface layers are removed. The surface analytical terms
covered in this document extend from the techniques of electron spectroscopy and mass spectrometry
to optical spectrometry and X-ray analysis. The terms covered in ISO 18115-2 relate to scanning-
probe microscopy. The terms covered in ISO 18115-3 relate to optical interface analysis. Concepts for
these techniques derive from disciplines as widely ranging as nuclear physics and radiation science to
physical chemistry and optics.
The wide range of disciplines and the individualities of national usages have led to different meanings
being attributed to particular terms and, again, different terms being used to describe the same concept.
To avoid the consequent misunderstandings and to facilitate the exchange of information, it is essential
to clarify the concepts, to establish the correct terms for use, and to establish their definitions.
The terms are classified under Clauses 3 to 22:
— Clause 3: Terms related to general concepts in surface chemical analysis;
— Clause 4: Terms related to particle transport in materials;
— Clause 5: Terms related to the description of samples;
— Clause 6: Terms related to sample preparation;
— Clause 7: Terms related to instrumentation;
— Clause 8: Terms related to experimental conditions;
— Clause 9: Terms related to sputter depth profiling;
— Clause 10: Terms related to resolution;
— Clause 11: Terms related to electron spectroscopy methods;
— Clause 12: Terms related to electron spectroscopy analysis;
— Clause 13: Terms related to X-ray fluorescence, reflection and scattering methods;
— Clause 14: Terms related to X-ray fluorescence, reflection and scattering analysis;
— Clause 15: Terms related to glow discharge methods;
— Clause 16: Terms related to glow discharge analysis;
— Clause 17: Terms related to ion scattering methods;
— Clause 18: Terms related to ion scattering analysis;
— Clause 19: Terms related to surface mass spectrometry methods;
— Clause 20: Terms related to surface mass spectrometry analysis;
— Clause 21: Terms related to atom probe tomography;
— Clause 22: Terms related to multivariate analysis.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 18115-1:2023(E)
Surface chemical analysis — Vocabulary —
Part 1:
General terms and terms used in spectroscopy
1 Scope
This part of the ISO 18115 series defines terms for surface chemical analysis. It covers general terms
and those used in spectroscopy, while ISO 18115-2 covers terms used in scanning-probe microscopy
and ISO 18115-3 covers terms used in optical interface analysis.
2 Normative references
There are no normative references in this document.
3 Terms related to general concepts in surface chemical analysis
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
interface
boundary between two phases having different chemical, elemental, or physical properties
3.2
surface
interface (3.1) between a condensed phase and a gas, vapour, or free space
3.3
measurand
quantity intended to be measured
[1]
[SOURCE: ISO/IEC Guide 99:2007, 2.3, modified — The notes to entry have been deleted.]
3.4
analyte
substance or chemical constituent that is subjected to measurement
3.5
chemical species
atom, molecule, ion, or functional group
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ISO/FDIS 18115-1:2023(E)
3.6
unified atomic mass unit
u
dalton
Da
12
unit equal to 1/12 of the mass of the nuclide C at rest and in its ground state
−27
Note 1 to entry: 1 u ≈ 1,660 538 86 × 10 kg with a one-standard-deviation uncertainty of ±0,000 000
−27 [2]
28 × 10 kg. This is a non-SI unit, accepted for use with the International System, whose value in SI units is
obtained experimentally.
Note 2 to entry: The term dalton, symbol Da, is preferred over unified atomic mass unit as it is both shorter and
works better with prefixes.
Note 3 to entry: The above definition was agreed upon by the International Union of Pure and Applied Physics
in 1960 and the International Union of Pure and Applied Chemistry in 1961, resolving a longstanding difference
between chemists and physicists. The unified atomic mass unit replaced the atomic mass unit (chemical scale)
and the atomic mass unit (physical scale), both having the symbol amu. The amu (physical scale) was one-
sixteenth of the mass of an atom of oxygen-16. The amu (chemical scale) was one-sixteenth of the average mass
of oxygen atoms as found in nature. In the 1998 CODATA, 1 u = 1,000 317 9 amu (physical scale) = 1,000 043 amu
(chemical scale).
3.7
reference method
thoroughly investigated method, clearly and exactly describing the necessary conditions and
procedures for the measurement of one or more property values, that has been shown to have accuracy
and precision commensurate with its intended use and that can therefore be used to assess the
accuracy of other methods for the same measurement, particularly in permitting the characterization
of a reference material (5.1)
[3]
[SOURCE: ISO Guide 30:1992+A1: 2008 ]
3.8
quantitative analysis
determination of the amount of analyte (3.4) detected in, or on, a sample
Note 1 to entry: The analytes can be elemental or compound in nature.
Note 2 to entry: The amounts can be expressed, for example, as atomic or mass percent, atomic or mass fraction,
mole or mass per unit volume, as appropriate or as desired.
Note 3 to entry: The sample material can be inhomogeneous so that a particular model structure may be assumed
in the interpretation. Details of that model should be stated.
3.9
detection limit
smallest amount of an element or compound that can be measured under specified analysis conditions
Note 1 to entry: The detection limit is often taken to correspond to the amount of material for which the total
signal for that material minus the background signal (3.21) is three times the standard deviation of the signal
above the background signal. This approach is simplistic and, for more accurate and rigorous definitions of
detection limits, the References [4] and [5] should be consulted.
Note 2 to entry: The detection limit can be expressed in many ways, depending on the purpose. Examples of ways
of expressing it are mass or weight fraction, atomic fraction, concentration, number of atoms, and mass or weight.
Note 3 to entry: The detection limit is generally different for different materials.
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ISO/FDIS 18115-1:2023(E)
3.10
matrix effects
change in the intensities or spectral information per atom of the analyte (3.4) arising from change in
the chemical or physical environment
Note 1 to entry: Examples of these environments are varying sample morphologies [e.g. thin films (5.13), clusters,
fibres, nanostructures] of different dimensions, the amorphous or crystalline state, changes of matrix species,
and the proximity of other physical phases or chemical species (3.5).
3.11
matrix factor
factors, arising from the composition of the matrix, for multiplying the quotient of the measured
intensity and the appropriate sensitivity factor in formulae to determine the composition using surface
analytical techniques
Note 1 to entry: See average matrix sensitivity factor and pure-element sensitivity factor.
Note 2 to entry: In methods such as AES (11.1), the matrix factor is determined in part by the composition of the
sub-surface material and in part by the composition of the analysis volume (8.48) in the sample.
3.12
absolute elemental sensitivity factor
coefficient for an element by which the measured intensity for that element is divided to yield the
atomic concentration or atomic fraction of the element present in the sample
Note 1 to entry: See elemental relative sensitivity factor (12.92) (20.61).
Note 2 to entry: The choice of atomic concentration or atomic fraction should be made clear.
Note 3 to entry: The type of sensitivity factor utilized should be appropriate for the formulae used in the
quantification process and for the type of sample analysed, for example homogeneous samples or segregated
layers.
Note 4 to entry: The source of sensitivity factors should be given to ensure that the correct matrix factors (3.11)
or other parameters are used.
Note 5 to entry: Sensitivity factors depend on parameters of the excitation source, the spectrometer, and the
orientation of the sample to these parts of the instrument. Sensitivity factors also depend on the matrix being
analysed, and in SIMS (19.1) this has a dominating influence.
3.13
step size
distance between values in measurand (3.3) space from which individual data points are acquired
3.14
sweep
single, complete acquisition of one set of data
3.15
peak intensity
measure of signal intensity (3.17) for a constituent spectral peak
Note 1 to entry: Intensity is usually measured for quantitative purposes which can be the height of the peak
above a defined background or the peak area (3.16). The units can be counts (3.18), counts⋅electron volts, counts
per second, counts⋅electron volts per second, counts per amu, counts per second per amu, etc. For differential
spectra, the intensity can be the peak-to-peak height or the peak-to-background height. The measure of intensity
should be defined and the units stated in each case.
Note 2 to entry: The meaning is very rarely the literal meaning of the intensity value at the top of the measured
peak either before or after removal of any background.
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ISO/FDIS 18115-1:2023(E)
3.16
peak area
area under a peak in a spectrum after background removal
Note 1 to entry: See inelastic electron scattering background subtraction (12.85) and signal intensity (3.17).
Note 2 to entry: The peak area can be expressed in counts (3.18), counts per second, counts⋅electron volts,
counts⋅electron volts per second, counts per amu, or other units.
3.17
signal intensity
strength of a measured signal at a spectrometer detector or after some defined processing
Note 1 to entry: The signal intensity is subject to significant change between the points of generation and
detection of the signal and, further, between the points of detection and display on the measuring instrument.
Note 2 to entry: The signal intensity can be expressed in counts (3.18) (per channel) or counts per second
(per channel) or counts⋅electron volts per second or other units. In AES (11.1), the differential of the signal
intensity may be obtained by analogue modulation (12.61) of an electrode in the spectrometer or by numerical
differentiation of the spectrum. The type of signal shall be defined.
Note 3 to entry: In an electron or mass spectrum (20.58), the measured spectrum integrated over energy or
mass and solid angle is equal to a current. If the spectrometer has been calibrated, the units of intensity can be
−1 −1 −1 −1
current⋅eV ⋅sr or current⋅amu ⋅sr . If the spectrum has been normalized to unit primary-beam (8.10) current,
−1 −1 −1 −1
the appropriate units would be eV ⋅sr or amu ⋅sr . If the spectrum has also been integrated over the emission
−1 −1
solid angle, the appropriate units would be eV or amu .
3.18
counts
total number of pulses recorded by a detector system in a defined time interval
Note 1 to entry: The counts can be representative, one-for-one with the particles being detected [in the absence
of dead time (7.17) losses in the counting measurement] in which case they follow Poissonian statistics [unless
other noise (3.19) sources are present] or they can simply be proportional to the number of particles being
detected. The type of measure shall be clearly stated.
Note 2 to entry: In multidetector systems, the apportion of counts into relevant channels of the spectrum can lead
to changes from the expected Poissonian statistics in each channel since the counts in neighbouring channels can
be partly correlated.
3.19
noise
time-varying disturbances superimposed on the analytical signal with fluctuations, leading to
uncertainty in the signal intensity (3.17)
Note 1 to entry: An accurate measure of noise can be determined from the standard deviation of the fluctuations.
Visual or other estimates, such as peak-to-peak noise in a spectrum, can be useful as semiquantitative measures
of noise.
Note 2 to entry: The fluctuations in the measured intensity can arise from a number of causes, such as statistical
noise (3.20) and electrical interference.
3.20
statistical noise
noise (3.19) in the spectrum due solely to the statistics of randomly detected single events
Note 1 to entry: For single-particle counting systems exhibiting Poisson statistics, the standard deviation of a
large number of measures of an otherwise steady count rate, N, each in the same time interval, is equal to the
square root of N.
Note 2 to entry: In multidetector systems, the data processing required to generate the output spectrum can lead
to statistical correlation between adjacent channels and also an apparent noise in each channel that is less than
Poissonian.
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ISO/FDIS 18115-1:2023(E)
3.21
background signal
signal present at a particular position, energy, mass or wavelength due to processes or sources other
than those of primary interest
Note 1 to entry: See metastable background (20.36), Shirley background (12.86), Sickafus background (12.87), and
Tougaard background (12.88).
3.22
peak-to-background ratio
signal-to-background ratio
ratio of the maximum height of the peak above the background intensity to the magnitude of that
background intensity
Note 1 to entry: Signal-to-background ratio is the more commonly used term in GDS (15.1), where it is abbreviated
to SBR. Peak-to-background ratio is the more commonly used term for types of electron spectroscopies such as
AES (11.1) and XPS (11.6).
Note 2 to entry: The method of estimating the background intensity shall be given. For AES, the background
intensity is often determined at a kinetic energy (3.35) just above the peak of interest.
3.23
signal-to-noise ratio
ratio of the signal intensity (3.17) to a measure of the total noise (3.19) in determining that signal
Note 1 to entry: See statistical noise (3.20).
Note 2 to entry: The noise in AES (11.1) is often measured at a convenient region of the spectral background close
to the peak.
3.24
smoothing
mathematical treatment of data to reduce the apparent noise (3.19)
3.25
interference signal
signal, measured at the mass, energy, or wavelength position of
interest, due to another, undesired, species
Note 1 to entry: In general laboratory use, interference can be used more broadly to indicate electrical noise
(3.19), line pick-up, or other unwanted contributions to the detected signal.
3.26
relative standard deviation of the background
quotient of the standard deviation characterizing the noise (3.19) in the background signal (3.21) by the
intensity of the background signal
3.27
lineshape
measured shape of a particular spectral feature
3.28
peak width
width of a peak at a defined fraction of the peak height
Note 1 to entry: See intrinsic linewidth (12.22).
Note 2 to entry: Any background subtraction method used should be specified.
Note 3 to entry: The most common measure of peak width is the full width of the peak at half maximum (FWHM)
intensity.
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ISO/FDIS 18115-1:2023(E)
Note 4 to entry: For asymmetrical peaks, convenient measures of peak width are the half-widths of each side of
the peak at half maximum intensity.
3.29
peak fitting
procedure whereby a spectrum, generated by peak synthesis (3.30), is adjusted to match a measured
spectrum
Note 1 to entry: A least-squares optimization procedure is generally used in a computer programme for this
purpose.
Note 2 to entry: The selected peak shape and the background shape should be defined. Any constraints imposed
on the adjustment process should also be defined.
3.30
peak synthesis
procedure whereby a synthetic spectrum is generated, using either model or experimental peak shapes,
in which the number of peaks, the peak shapes, the peak widths (3.28), the peak positions, the peak
intensities, and the background shape and intensity are adjusted for peak fitting (3.29)
Note 1 to entry: The selected peak shape and the background shape should be defined.
3.31
lateral profile
chemical or elemental composition, signal intensity (3.17) or processed intensity information from the
available software measured in a specified direction parallel to the surface (3.2)
Note 1 to entry: See line scan (8.56).
3.32
depth profile
vertical profile
chemical or elemental composition, signal intensity (3.17) or processed intensity information from the
available software measured in a direction normal to the surface (3.2)
Note 1 to entry: See compositional depth profile (3.33).
3.33
compositional depth profile
CDP
atomic or molecular composition measured as a function of distance normal to the surface (3.2)
3.34
depth profiling
monitoring of signal intensity (3.17) as a function of a variable that can be related to distance normal to
the surface (3.2)
Note 1 to entry: See compositional depth profile (3.33).
Note 2 to entry: In a sputter depth profile (9.1) the signal intensity is usually measured as a function of the
sputtering (9.3) time.
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ISO/FDIS 18115-1:2023(E)
3.35
kinetic energy
energy of motion
Note 1 to entry: The energy of a charged particle due to motion is not necessarily constant and varies with the
local electric potential. If all local electrodes are at ground potential, the kinetic energy of the particle varies
with the local vacuum level (12.10). This vacuum level can vary over a range of 1 eV in different regions of AES
(11.1) and XPS (11.6) instruments and measured electron energies can similarly vary. This variation is removed
if the kinetic energies are referred to the Fermi level (12.9). In XPS, by convention, the Fermi level is always used
but in AES both vacuum (12.76) and Fermi level referencing (12.75) are practised. Instruments capable of both
AES and XPS are Fermi level referenced. Fermi level referencing is recommended for accurate measurements of
energies in AES. In electron spectrometers (12.58), Fermi level referenced energies are typically 4,5 eV greater
than those referenced to the vacuum level. It is convenient in AES to assume a standard vacuum level (12.11) of
4,500 eV above the Fermi level s
...