ISO 18115:2001

INTERNATIONAL ISO
STANDARD 18115
First edition
2001-07-15
Surface chemical analysis — Vocabulary
Analyse chimique des surfaces — Vocabulaire
Reference number
©
ISO 2001
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Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Abbreviations.1
3 Format.2
4 Definitions of the surface analysis methods .2
5 Definitions of terms for surface analysis .4
Annex A (informative) Extract from IEC 60050-111, International Electrotechnical Vocabulary —
Chapter 111: Physics and Chemistry .50
Bibliography.52
Alphabetical index of terms.53
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
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Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 18115 was prepared by Technical Committee ISO/TC 201, Surface chemical analysis,
Subcommittee SC 1, Terminology.
Annex A of this International Standard is for information only.
iv © ISO 2001 – All rights reserved

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 may be materials scientists,
chemists or physicists and may 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 techniques covered in this International
Vocabulary extend from electron spectroscopy and mass spectrometry to optical spectrometry and X-ray 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 work for ISO 18115 started with a consideration, inter alia, of ASTM E 673-95a, Standard terminology relating
[1]
to surface analysis , and a number of terms retain this reference. Such definitions have remained essentially
unchanged. Some editorial changes have had to be made in all the cases where this reference appears since the
ASTM definition structure differs from that adopted by ISO. Some other terms from the ASTM standard also
appear, but with a revised text or significantly revised meaning. These terms are not referenced to the ASTM
standard.
The terms of this International Vocabulary standard have been prepared in conformance with the principles and style
defined in ISO 1087-1:2000, Terminology work — Vocabulary — Part 1: Theory and Application, and
ISO 10241:1992, International terminology standards — Preparation and layout. Essential aspects of these standards
appear in subclauses 3.1 to 3.3. The terms are given in alphabetical order, classified under two headings:
Clause 4: Definitions of the surface analysis methods.
Clause 5: Definitions of terms for surface analysis.
Additional terms, important for surface analysis, are given in an extract from IEC 60050-111 in annex A.
A single alphabetical index is given after the Bibliography. To assist retrieval, compound terms may be found in the
index in both natural and reverse word order.
As standards are formulated by Technical Committee ISO/TC 201, Surface chemical analysis, new terms are defined.
It is intended that these terms will be grouped conveniently into a supplement or supplements, to be used with this
standard, until such time as this standard needs to be revised when they will be incorporated.
INTERNATIONAL STANDARD ISO 18115:2001(E)
Surface chemical analysis — Vocabulary
1 Scope
This International Standard defines terms for surface chemical analysis.
2 Abbreviations
AES Auger electron spectroscopy
CDP compositional depth profile
CMA cylindrical mirror analyser
eV electron volt
EELS electron energy loss spectroscopy
EIA energetic-ion analysis
EPMA electron probe microanalysis
ESCA electron spectroscopy for chemical analysis
FABMS fast atom bombardment mass spectrometry
FWHM full width at half maximum
GDS glow discharge spectrometry
GDOES glow discharge optical emission spectrometry
GDMS glow discharge mass spectrometry
HEISS high-energy ion-scattering spectrometry
HSA hemispherical sector analyser
IBA ion beam analysis
LEISS low-energy ion-scattering spectrometry
MEISS medium-energy ion-scattering spectrometry
ptp peak-to-peak
RBS Rutherford backscattering spectrometry
RFA retarding field analyser
SAM scanning Auger microscope
SDP sputter depth profile
SEM scanning electron microscope
SIMS secondary-ion mass spectrometry
SNMS sputtered neutral mass spectrometry
SSA spherical sector analyser
TOF or ToF time of flight
TXRF total-reflection X-ray fluorescence spectroscopy
UPS ultra-violet photoelectron spectroscopy
XPS X-ray photoelectron spectroscopy
3 Format
3.1 Use of terms printed boldface in definitions
A term printed boldface in a definition or a note is defined in another entry in this International Standard. However, the
term is printed boldface only the first time it occurs in each entry.
3.2 Non-preferred and deprecated terms
A term listed lightface is non-preferred or deprecated. The preferred term is listed boldface.
3.3 Subject fields
Where a term designates several concepts, it is necessary to indicate the subject field to which each concept
belongs. The field is shown lightface, between angle brackets, preceding the definition, on the same line.
4 Definitions of the surface analysis methods
4.1
Auger electron spectroscopy
AES
a method in which an electron spectrometer is used to measure the energy distribution of Auger electrons
emitted from a surface
NOTE An electron beam in the energy range 2 keV to 30 keV is often used for excitation of the Auger electrons. Auger
electrons can also be excited with X-rays, ions and other sources but the term Auger electron spectroscopy, without additional
qualifiers, is usually reserved for electron-beam-induced excitations. Where an X-ray source is used, the Auger electron
energies are referenced to the Fermi level but, where an electron beam is used, the reference may either be the Fermi level or
the vacuum level. Spectra conventionally may be presented in the direct or differential forms.
4.2
dynamic SIMS
SIMS in which the material surface is sputtered at a sufficiently rapid rate that the original surface cannot be
regarded as undamaged during the analysis
NOTE 1 Dynamic SIMS is often simply termed SIMS.
16 2
NOTE 2 The ion areic dose during measurement is usually more than 10 ions/m .
2 © ISO 2001 – All rights reserved

4.3
electron spectroscopy for chemical analysis (deprecated)
ESCA (deprecated)
a method encompassing both AES and XPS
NOTE The term ESCA has fallen out of use as, in practice, it was only used to describe situations more clearly defined by
the term X-ray photoelectron spectroscopy (XPS). Since 1980, the latter term has been preferred.
4.4
fast atom bombardment mass spectrometry
FABMS
FAB (deprecated)
a method in which a mass spectrometer is used to measure the mass-to-charge quotient and abundance of
secondary ions emitted from a sample as a result of the bombardment by fast neutral atoms
4.5
glow discharge mass spectrometry
GDMS
a method in which a mass spectrometer is used to measure the mass-to-charge quotient and abundance of ions
from a glow discharge generated at a surface
4.6
glow discharge optical emission spectrometry
GDOES
a method in which an optical emission spectrometer is used to measure the wavelength and intensity of light
emitted from a glow discharge generated at a surface
4.7
glow discharge spectrometry
GDS
a method in which a spectrometer is used to measure relevant intensities emitted from a glow discharge
generated at a surface
NOTE This is a general term which encompasses GDOES and GDMS.
4.8
ion beam analysis
IBA
a method to elucidate composition and structure of the outermost atomic layers of a solid material, in which
principally monoenergetic, singly charged probe ions, scattered from the surface are detected and recorded as a
function of their energy or angle of scattering,orboth
NOTE LEISS, MEISS and RBS are all forms of IBA in which the probe ion energies are typically in the ranges 0,1 keV to
10 keV, 50 keV to 200 keV and 1 MeV to 2 MeV, respectively. These classifications represent three ranges in which
fundamentally different physics is involved.
4.9
secondary-ion mass spectrometry
SIMS
a method in which a mass spectrometer is used to measure the mass-to-charge quotient and abundance of
secondary ions emitted from a sample as a result of bombardment by energetic ions
cf. dynamic SIMS, static SIMS
NOTE SIMS is, by convention, generally classified as dynamic, in which the material surface layers are continually removed
16 2
as they are being measured, and static, in which the ion areic dose during measurement is restricted to less than 10 ions/m
in order to retain the surface in an essentially undamaged state.
4.10
sputtered neutral mass spectrometry
SNMS
a method in which a mass spectrometer is used to measure the mass-to-charge quotient and abundance of
secondary ionized neutral species emitted from a sample as a result of particle bombardment
NOTE The neutral species may be detected by using plasma, electron, or photon ionization methods.
4.11
static SIMS
SIMS in which the material surface is sputtered at a sufficiently low rate that the original surface is insignificantly
damaged during the analysis
cf. dynamic SIMS
16 2
NOTE The ion areic dose during measurement is restricted to less than 10 ions/m to an extent that depends on both the
material of the sample and the size of the molecular fragments being analysed.
4.12
total reflection X-ray fluorescence spectroscopy
TXRF
a method in which an X-ray spectrometer is used to measure the energy distribution of fluorescence X-rays
emitted from a surface irradiated by primary X-rays under the condition of total reflection
4.13
ultra-violet photoelectron spectroscopy
UPS
a method in which an electron spectrometer is used to measure the energy distribution of photoelectrons emitted
from a surface irradiated by ultra-violet photons
NOTE Ultra-violet sources in common use include various types of discharges that can generate the resonance lines of
various gases (e.g. the He I and He II emission lines at energies of 21,2 eV and 40,8 eV, respectively). For variable energies,
synchrotron radiation is used.
4.14
X-ray photoelectron spectroscopy
XPS
a method in which an electron spectrometer is used to measure the energy distribution of photoelectrons and
Auger electrons emitted from a surface irradiated by X-ray photons
NOTE X-ray sources in common use are Al and Mg unmonochromated K� X-rays at 1 486,6 and 1 253,6 eV, respectively.
Modern instruments also use monochromated Al K� X-rays. Some instruments make use of various X-ray sources with other
anodes or of synchrotron radiation.
5 Definitions of terms for surface analysis
5.1
absorption coefficient, linear
linear attenuation coefficient
5.2
absorption coefficient, mass
attenuation coefficient, mass
�TXRF, XPS� quantity �/� in the expression (�/�)�(�x) for the fraction of a parallel beam of specified particles or
radiation removed in passing through a thin layer of mass thickness �(�x) of a substance in the limit as �(�x)
approaches zero, where �(�x) is measured in the direction of the beam
cf. attenuation length
NOTE 1 The mass density of the substance is� and x is the distance in the direction of the beam.
4 © ISO 2001 – All rights reserved

NOTE 2 The intensity or number of particles in the beam decays as exp(–�x) with the distance x.
NOTE 3 The mass attenuation (absorption) coefficient is the quotient of the linear attenuation (absorption) coefficient and the
mass density of the substance.
5.3
adventitious carbon referencing
�XPS� determining the charging potential of a particular sample from a comparison of the experimentally
determined C 1s binding energy, arising from adsorbed hydrocarbons on the sample, with a standard binding
energy value
cf. internal carbon referencing
NOTE A nominal value of 285,0 eV is often used for the binding energy of the relevant C 1s peak, although some analysts
prefer specific values in the range 284,6 eV to 285,2 eV depending on the nature of the substrate.
5.4
altered layer
�particle bombardment� surface region of a material under particle bombardment where the chemical state or
physical structure is modified by the effects of the bombardment
+
EXAMPLE For silicon bombarded by 4 keV O at near normal incidence, after sputtering for a sufficient time to reach a
steady state, the surface is converted to stoichiometric SiO to a depth of around 15 nm with lower oxygen concentrations at
greater depths.
5.5
analysis area
�sample� two-dimensional region of a sample surface measured in the plane of that surface from which the entire
analytical signal or a specified percentage of that signal is detected
5.6
analysis area
�spectrometer� two-dimensional region of a sample surface at the analytical point but set in the plane at right
angles to the spectrometer axis from which the entire analytical signal or a specified percentage of that signal is
detected
5.7
analysis volume
�sample� three-dimensional region of a sample from which the entire analysis signal or a specified percentage of
that signal is detected
5.8
analysis volume
�spectrometer� three-dimensional region within the spectrometer from which the entire analytical signal or a
specified percentage of that signal may be detected
5.9
angle, critical
�TXRF� glancing angle at which the sample matrix X-ray fluorescence, when plotted against the glancing angle, is
at the first point of inflection
5.10
angle, glancing
�TXRF� angle between the incident beam and the average surface plane
NOTE Angle of incidence and glancing angle are complementary.
5.11
angle lapping
sample preparation in which a sample is mechanically polished at an angle to the original surface
cf. ball cratering, radial sectioning
NOTE This angle may often be less than 1° so that depth information with respect to the original surface is transformed to
lateral information.
5.12
angle, magic
�XPS� angle at which the spectrometer entrance axis is aligned at 54,7° to the direction of the X-rays at the sample
surface
NOTE At the magic angle, using the simple dipole theory for the angular distribution of the photoelectrons emitted from an
isolated atom irradiated by unpolarized X-rays, it is predicted that the intensity per unit solid angle is the same as the intensity
that would be obtained if the scattering were isotropic.
5.13
angle of emission
angle between the trajectory of a particle or photon as it leaves a surface and the local or average surface normal
NOTE The particular surface normal needs to be specified.
5.14
angle of incidence
angle between the incident beam and the local or average surface normal
NOTE The particular surface normal, such as the surface normal to an elementary portion of a rough surface or the normal
to the average surface plane, needs to be specified.
5.15
angle of scattering
angle between the direction of the incident particle or photon and the direction that the particle or photon is
travelling after scattering
5.16
angle-resolved AES
ARAES
angle-dependent AES
a procedure in which Auger electron intensities are measured as a function of the angle of emission
5.17
angle-resolved XPS
ARXPS
angle-dependent XPS
a procedure in which X-ray photoelectron intensities are measured as a function of the angle of emission
NOTE This procedure is often used to obtain information on the distribution with depth of different elements or compounds
in a layer approximately 5 nm thick at the surface.
5.18
angle, solid, of analyser
solid angle of analyser that will transmit particles or photons from a point on the sample to the detector
cf. analyser transmission function
5.19
angle, solid, of detector
�EIA, RBS� solid angle intercepted by the detector from an origin at the centre of the beam spot
6 © ISO 2001 – All rights reserved

5.20
angle, take-off
angle between the trajectory of a particle as it leaves a surface and the local or average surface plane
NOTE 1 The particular surface plane needs to be specified.
NOTE 2 Take-off angle is the complement of angle of emission.
NOTE 3 In the past, take-off angle has sometimes been used erroneously to mean angle of emission.
5.21
asymmetry parameter
�
�XPS� factor which characterizes the intensity distribution, L(� ), of photoelectrons ejected by unpolarized X-rays
from isolated atoms in a direction � from the incident X-ray direction according to
��
L��=1+1/2 3 2 sin� �1
� � � �
��
��
��
NOTE This formula relates to gases and is modified by the effects of elastic scattering when applied to solids.
5.22
atomic mixing
migration of sample atoms due to energy transfer with incident particles in the surface region
cf. cascade mixing, collision cascade, ion-beam-induced mass transport, knock-on, recoil implantation
5.23
attenuation coefficient
quantity � in the expression ��x for the fraction of a parallel beam of specified particles or radiation removed in
passing through a thin layer �x of a substance in the limit as �x approaches zero, where �x is measured in the
direction of the beam
cf. attenuation length, mass absorption coefficient
NOTE 1 The intensity or number of particles in the beam decays as exp(–�/x�) with the distance x.
NOTE 2 Attenuation coefficient is often used in place of linear attenuation coefficient and is used in EPMA. Both are the
reciprocal of attenuation length which is used in AES and XPS.
5.24
attenuation length
quantity l in the expression �x/l for the fraction of a parallel beam of specified particles or radiation removed in
passing through a thin layer �x of a substance in the limit as �x approaches zero, where �x is measured in the
direction of the beam
cf. attenuation coefficient, decay length, effective attenuation length, electron inelastic mean free path, linear
absorption coefficient, mass absorption coefficient
NOTE 1 The intensity or number of particles in the beam decays as exp(– x/l) with the distance x.
NOTE 2 For electrons in solids, the behaviour only approximates an exponential decay due to the effects of elastic
scattering. Where this approximation is valid, the term effective attenuation length is used.
5.25
attenuation length, effective
average emission function decay length when the emission depth distribution function is sufficiently close to
exponential for a given application
cf. attenuation length
NOTE Effective attenuation length is often used in AES and XPS to describe the transport of electrons that have not lost
more than 1 eV as a result of inelastic scattering.
5.26
Auger de-excitation
�surface�
a) process in which the energy of an excited atom or ion is given up by a non-radiative re-arrangement of
electrons in that atom or ion
b) process in which the energy in a metastable species near a solid surface is lost by interaction with the surface,
and in the process enough energy is released to eject an electron from a surface atom
cf. Auger neutralization
NOTE For both processes, the electron may be ejected into the vacuum.
5.27
Auger electron
electron emitted from atoms in the Auger process
cf. Auger transition
NOTE 1 Auger electrons can lose energy by inelastic scattering as they pass through matter. Measured Auger electron
spectra are therefore generally composed of a peak structure of unscattered Auger electrons superimposed on a background of
inelastically scattered Auger electrons with intensities extending to lower kinetic energies, and on backgrounds arising from
other processes.
NOTE 2 Auger electrons may change their direction of propagation by elastic scattering as they pass through matter.
5.28
Auger electron spectrum
plot of the Auger electron intensity as a function of the electron kinetic energy, usually as part of the energy
distribution of detected electrons
NOTE 1 When excited by incident electrons, the energy distribution of detected electrons, often measured between 0 eV and
2 500 eV, contains Auger electrons, backscattered (primary) electrons and secondary electrons. The entire distribution is
sometimes referred to as an Auger electron spectrum.
NOTE 2 The Auger electron spectrum may be presented in either the direct spectrum or differential spectrum formats.
5.29
Auger electron yield
[1]
probability that an atom with a vacancy in a particular inner shell will relax by an Auger process
5.30
Auger neutralization
�ion at a surface� a process in which an electron, tunnelling from the conduction band of a solid, neutralizes an
incoming ion and an electron is ejected from a surface atom
NOTE The ejected electron may be emitted into the vacuum.
5.31
Auger parameter
�XPS� kinetic energy of a narrow Auger electron peak in a spectrum minus the kinetic energy of the most intense
photoelectron peak from the same element
cf. initial state Auger parameter, modified Auger parameter
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NOTE 1 The value of the Auger parameter depends on the energy of the X-rays which therefore needs to be specified.
NOTE 2 The Auger parameter is sometimes called the final state Auger parameter.
NOTE 3 The Auger parameter is useful for separating chemical states for samples in which charging causes uncertainty in
the binding energy measurement or in which the binding energy shift is inadequate to identify the chemical state.
NOTE 4 The Auger parameter is useful for evaluating the relaxation energy of the ionized matrix atom associated with the
generation of a core hole for those Auger transitions between core levels which have similar chemical shifts.
5.32
Auger parameter, initial state
�XPS� �,where �=3E + E and where E and E are, respectively, the binding energy of a photoelectron peak
B K B K
and the Fermi level referenced kinetic energy of an Auger electron peak, each involving the same initial core
level of the same element
cf. Auger parameter, modified Auger parameter
NOTE The initial state Auger parameter is useful for evaluating the change in the atomic core potential contribution to
changes in binding energy between two environments, providing the Auger transition is between core levels which have similar
binding energy shifts.
5.33
Auger parameter, modified
�XPS� sum of the Fermi level referenced kinetic energy of a narrow Auger electron peak in the spectrum and the
binding energy of the most intense photoelectron peak from the same element
cf. Auger parameter, initial state Auger parameter
NOTE The modified Auger parameter is the sum of the Auger parameter and the energy of the X-rays responsible for the
measured photoelectron peak. Unlike the Auger parameter, it does not depend on the energy of the X-rays.
5.34
Auger process
[1]
relaxation, by electron emission, of an atom with a vacancy in an inner electron shell
cf. Auger de-excitation, Auger electron, Auger transition
NOTE The emitted electrons have characteristic energies, defined by the Auger transition.
5.35
Auger process, interatomic
�AES� Auger transition in which at least one of the final electron vacancies is localized in valence levels or
molecular orbitals of atoms adjacent to the atom in which the initial vacancy occurred
5.36
Auger transition
Auger process involving designated electron shells or sub-shells
NOTE 1 The three shells involved in the Auger process are designated by three letters. The first letter designates the shell
containing the initial vacancy and the last two letters designate the shells containing electron vacancies left by the Auger
process (for example, KLL, and LMM). When a valence electron is involved, the letter V is used (for example, LMV and KVV).
When a particular sub-shell involved is known, this can also be indicated (for example, KL L ). Coupling terms may also be
1 2
added, where known, to indicate the final atomic state (for example, L M M ; D).
3 4,5 4,5
NOTE 2 More complicated Auger processes (such as multiple initial ionizations and additional electronic excitations) can be
designated by separating the initial and final states by a dash (for example, LL-VV and K-VVV).
NOTE 3 When an Auger process involves an electron from the same principal shell as the initial vacancy (for example,
L L M),itisreferredtoasa Coster-Kronig transition. If all electrons are from the same principal shell (for example, M M M ),
1 2 1 2 3
the process is called a super Coster-Kronig transition.
5.37
Auger transition rate
quotient of the probability for an Auger process by time
5.38
background, inelastic
intensity distribution in the spectrum for particles originally at one energy but which are emitted at lower energies
due to one or more inelastic scattering processes
cf. inelastic scattering background subtraction, Shirley background, Sickafus background, Tougaard
background
NOTE For AES and XPS, the inelastic background associated with a particular Auger electron or photoelectron peak has
been approximated by a measured electron energy loss spectrum for which the incident-electron energy is close to the energy
of the peak. The Tougaard background is also used. A simpler, but less accurate, inelastic background function is the Shirley
background. Simple linear backgrounds have also been used but these are much less accurate, except for the XPS analysis of
insulators.
5.39
background, instrumental
intensity contribution, generally unwanted, arising from non-ideal behaviour of one or more parts of the instrument
5.40
background, Shirley
�AES, XPS� background calculated to fit the measured spectrum at points at higher and lower kinetic energy than
the peak or peaks of interest such that the background contribution at a given kinetic energy is in a fixed
proportion to the total peak area above that background for higher kinetic energies
cf. Tougaard background
5.41
background, Sickafus
�AES, XPS� single-term power law background designed to describe the intensity of the secondary-electron
cascade as a function of electron emission kinetic energy
NOTE 1 The measured secondary-electron cascade, for correct application of the Sickafus background, should be the
experimentally observed spectrum corrected for the spectrometer response function of the measuring instrument.
NOTE 2 The spectrum shape, for a Sickafus background B (E), is given by
S
�m
BE���E
S
where E is the electron emission kinetic energy and m is a number in the range 1 to 2.
5.42
background signal
signal present at a particular position, energy, mass or wavelength due to processes or sources other than those of
primary interest
cf. Shirley background, Sickafus background, Tougaard background
5.43
background, Tougaard
�AES, XPS� intensity distribution obtained from a model for the differential inelastic scattering cross-section with
respect to energy loss and the three-dimensional distribution of the emitting atoms in the surface region
cf. Shirley background
NOTE 1 A number of classes of atomic distributions may be used together with different differential inelastic scattering cross-
sections. The atomic distribution and the inelastic scattering cross-section should be specified.
10 © ISO 2001 – All rights reserved

NOTE 2 The Tougaard background is usually calculated to match the measured spectrum over a wide energy range that
excludes the peak region and the spectral region extending to approximately 50 eV less kinetic energy than the peaks of
interest. The measured spectrum should be corrected for the spectrometer response function of the measuring instrument
before calculation of the Tougaard background.
5.44
backscattered electron
�AES, EELS� electron originating in the incident beam which is emitted after interaction with the sample
NOTE 1 By convention, an electron with energy greater than 50 eV may be considered as a backscattered electron.
NOTE 2 By convention, the incident beam is often called the primary beam and the backscattered electrons are often
referred to as the backscattered primary electrons.
5.45
backscattering coefficient
backscattering yield
�EIA, RBS� quotient of the number of detected particles in an interval of backscattering energy by that interval and
by the number of incident ions
5.46
backscattering energy
energy of a particle from the primary beam after it has undergone a backscattering collision and escaped from the
sample
5.47
backscattering factor
�AES� factor defining the increase in the Auger electron current due to additional ionizations in the sample caused
by backscattered electrons above that arising directly from the primary electrons
NOTE Different usages exist; the factor is commonly the fractional increase, as defined above, and sometimes unity plus
that fractional increase. The latter usage is deprecated. For clarity, the particular usage needs to be defined.
5.48
backscattering spectrum
[1]
�EIA, RBS� plot of backscattering yield versus backscattering energy
5.49
backscattering yield
backscattering coefficient
�
�AES, EPMA� ratio of the total number of electrons emitted from the sample with energies greater than 50 eV to the
total number of electrons incident at a given energy and angle of incidence
cf. secondary-electron yield, total secondary-electron yield, backscattering factor
5.50
ball cratering
a procedure in which the sample is abraded by a sphere in order to expose compositional changes in layers below
the original surface with the intent that the depth of those layers can be related to the lateral position in the crater
created by the abrasion
cf. angle lapping, radial sectioning
5.51
beam convergence angle
angular interval containing all or a specified fraction of the beam in the space prior to or at the focal plane
cf. beam divergence angle
NOTE Where the beam is symmetrical, the full or semi-angle may be used. The particular measure of angle needs to be
stated.
5.52
beam current
I
quotient of dQ by dt, where dQ is the quantity of electric charge of a specified polarity in the beam passing in the
time interval dt
IQ�ddt
cf. pulse beam current, average beam current
NOTE For beams in which the current varies with time, the instantaneous and time-averaged beam currents will generally
differ. For a pulsed beam, the current when the beam is on may or may not be equal to the d.c. or unpulsed beam current.
5.53
beam current, average
quotient of Q by t, where Q is the quantity of electric charge of a specified polarity in the beam passing in the time
interval t
NOTE For beams in which the instantaneous current varies periodically with time, the time interval t is an integral number
of periods.
5.54
beam current density
J
�for a parallel beam of charged particles� quotient of dI by dA where dI is the element of beam current incident on
an area dA at right angles to the direction of the beam
JI�ddA
cf. fluence, flux, dose
NOTE For a convergent or divergent beam, the area dA is replaced by a small sphere of cross-sectional area dA.
5.55
beam current, integrated
total electric charge transported in the beam over a specified time
5.56
beam current, pulse
quotient of Q by t where Q is the quantity of electric charge of a specified polarity in the beam passing during the
p
period t in which the pulse is on
p
5.57
beam diameter
�for a particle beam of circular cross-section� full width of the beam at half maximum intensity measured in a plane
[1]
normal to the beam direction
NOTE The beam diameter is usually specified at a given point in space such as the position of the sample.
5.58
beam divergence angle
angular interval containing all or a specified fraction of the beam in the space after the focal plane
cf. beam convergence angle
NOTE Where the beam is symmetrical, the full or semi-angle may be used. The particular measure of angle needs to be
stated.
12 © ISO 2001 – All rights reserved

5.59
beam energy
kinetic energy of the beam particles
cf. beam impact energy, incident-particle energy
NOTE 1 The energy is usually given in electron volts.
NOTE 2 The beam energy is often taken to be the particle energy on impact at the sample surface. However, where a
sample is at a potential other than ground, the impact energy of the particles may differ from the beam energy as delivered by
an electron or ion gun to the sample environment. In this case, use of the term impact energy avoids confusion.
5.60
beam impact energy
kinetic energy of the beam particles on impact with the sample surface
cf. beam energy, incident-particle energy
NOTE 1 For primary ion beams in SIMS, the beam impact energy is given by the difference in electric potential between the
ion source, strictly the plasma meniscus, and the sample surface multiplied by the charge on the ion. In some SIMS systems,
the beam energy is given for the source potential with respect to ground but the sample potential need not be at ground. The
impact energy takes account of any sample potential.
NOTE 2 Use of the qualifier “impact” indicates that this is the energy of the particles striking the surface.
5.61
beam particle
electron, positron, ion, atomic, molecular or cluster species contained in the incident beam
5.62
beam, primary
directed flux of particles or photons incident on a sample
5.63
beam profile
spatial distribution of the beam flux in a plane normal to the beam axis
5.64
binary elastic scattering
elastic scattering
collision between a moving particle and a second particle in which the total kinetic energy and the total momentum
are conserved
cf. inelastic scattering
NOTE In elastic scattering interactions, the moving particle may be deflected through angles of up to 180°.
5.65
binary elastic scattering peak
�ISS� increase in the spectrometer detection system response above the background level which can be attributed
[1]
to binary elastic scattering of an incident ion by a surface atom of a particular mass
5.66
binding energy
energy that must be expended in removing an electron from a given electronic level to the Fermi level of a solid or
to the vacuum level of a free atom or molecule
5.67
blocking geometry
�EIA, RBS� experimental arrangement wherein the atom rows or planes of a single crystal target are aligned
[1]
parallel to a vector from the sample to the detector
5.68
Bragg's rule
empirical rule formulated by W.H. Bragg and R. Kleeman that states that the stopping cross-section of a
compound sample is equal to the sum of the products of the elemental stopping cross-sections for each constituent
and its atomic fraction, that is,
��AB��xy�
��xy AB
where ��(A B ) is the stopping cross-section of the compound, A B ,and � and � are the stopping cross-sections
x y x y A B
[1]
of elements A and B, respectively
5.69
bremsstrahlung
�EPMA, XPS� photon radiation emitted from a material due to the deceleration of incident electrons within that
material
NOTE 1 The bremsstrahlung radiation has a continuous spectral distribution up to the energy of the incident electrons.
NOTE 2 In XPS, The bremsstrahlung from a conventional X-ray source with an Al or Mg anode leads to a continuous
photoelectron background. This radiation may also photoionize inner shells that would be energetically impossible by
characteristic Al or Mg K� X-rays. As a result, Auger electron features may appear at negative binding energy values and, in
addition, the intensities of other Auger electron features may be greater than if the inner shell vacancies had been created only
by the characteristic X-rays. The bremsstrahlung-excited Auger electron features can be helpful in determining the various
Auger parameters needed to identify chemical states.
5.70
cascade mixing
a diffusion-like process in which atoms of material are moved randomly by energy deposited by incident particles
slowing down in the sample surface region
cf. atomic mixing, collision cascade, knock-on, recoil implantation
NOTE 1 If atomic mixing and knock-on effects are not significant, the measured sputter depth profile of a delta layer will be
asymmetric on account of cascade mixing since the surface moves through the sample as it is sputtered. The initial internal
profile produced will be Gaussian, however until significant delta material has been lost through the sample surface.
NOTE 2 If cascade mixing is the only significant mixing process, the centroid of the measured distribution will lie at the true
delta position (after any shift in the depth scale arising from pre-equilibrium effects has been corrected).
NOTE 3 In the dilute limit, the measured depth profile for the delta layer will have an exponential tail because any internal
atom has an equal probability of being moved deeper or shallower and there is thus an indefinitely persistent but decaying
concentration in the near-surface region. The presence of this tail often leads to the belief that there is a directional knock-on
process at work. True knock-on effects have rarely if ever been observed, and are probably not significant as causes of sputter
profile distortion.
5.71
channelling
preferential motion of energetic particles along certain axial or planar directions of a crystalline solid as the particles
move through the sample
NOTE The potentials of the individual atoms of the solid combine to reduce the scattering of the energetic particles from
these directions.
14 © ISO 2001 – All rights reserved

5.72
characteristic electron energy losses
�AES, EELS, XPS� inelastic scattering of electrons in solids that produces a non-uniform energy loss spectrum
determined by the characteristics of the material
cf. plasmon
NOTE 1 The most probable characteristic losses arise from excitation of valence electrons. For some solids (for example,
non-transition metals), inelastic scattering is dominated by plasmon excitations. For other solids, the inelastic scattering may be
due to a combination of plasmon excitation and single valence-electron excitations, and these excitations may not be
distinguishable. Inelastic scattering can also occur through the excitation of core level electrons when this is energetically
possible.
NOTE 2 The characteristic energy losses are most prominent in the energy loss range 0 eV to 100 eV.
NOTE 3 Characteristic electron energy loss peaks are often observed in association with other peaks in a spectrum (e.g.
Auger electron peaks, photoelectron peaks, and the peak arising from elastic scattering of primary electrons).
5.73
characteristic X-rays
phot
...