Definitions

The following are informal definitions, though we have tried to keep close to the formal definition. We have also tried to explain the different terms and abbriviations in their context. In no case can our informal definition replace the use of the formal definition given by official bodies such as the International Standards Organisation (ISO).
More terms are listed here


Term

Definition

a

 

accuracy

measure of how well a measured value agrees with the accepted value

AES

Auger Electron Spectroscopy, AES, is a surface analytical method. In AES the sample surface is bombarded with an electron beam and the energy distribution of Auger electrons emitted from a surface is measured with an electron spectrometer. An Auger electron is an electron emitted from atoms in the Auger process. The Auger electron spectrum describes intensity of the Auger electrons as a function of the electron kinetic energy. When excited by incident electrons, the energy distribution of detected electrons is often measured between 0 eV and 2 500 eV. It contains Auger electrons, backscattered (primary) electrons and secondary electrons. The entire distribution is sometimes referred to as an Auger electron spectrum. The Auger electron spectrum can be presented in either the direct spectrum or differential spectrum formats. The Auger electron yield is probability that an atom with a vacancy in a particular inner shell will relax by an Auger process
Once the Auger electrons are released from the atom, they can lose part of their 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. Additional background components arising from other processes may be observed. Auger electrons may change their direction of propagation by elastic scattering as they pass through matter.
The Auger process is understood as the relaxation of an atom with a vacancy in an inner electron shell by emission of an electron, the Auger electron. The emitted electrons have characteristic energies, defined by the Auger transition, i.e. the energies of the electron shells and sub-shells involved in the Auger Process. 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). The letter V indicates that a valence shell electron is involved (for example, LMV and KVV). When a particular sub-shell involved is known, this can also be indicated (for example, KL1L2). Coupling terms may also be added to indicate the final atomic state (for example, L3M4.5M4.5;1D). More complicated Auger processes (such as multiple initial ionisations and additional electronic excitations) can be designated by separating the initial and final states by a dash.
When an Auger process involves an electron from the same principal shell as the initial vacancy (for example, L1L2M), it is referred to as a Coster-Kronig transition. If all electrons are from the same principal shell (for example, M1M2M3), the process is called a super Coster-Kronig transition.
An interatomic Auger process is understood to involve several atoms. At least one of the final electron vacancies must be localised in valence levels or molecular orbitals of atoms adjacent to the atom in which the initial vacancy occurred.
There are two possibilities for Auger de-excitation at the surface of a solid. In the first process, the energy of an excited atom or ion is released by a non-radiative re-arrangement of electrons in that atom or ion. In the second process the energy of a metastable species near a solid surface is lost through interaction with the surface. In this case enough energy must be released to eject an electron from a surface atom.
Auger neutralisation of an ion at a surface is understood as the process in which an electron ejected from a surface atom, after tunnelling from the conduction band of the solid and neutralising the incoming ion.
In all these processes the released electron may be ejected into the vacuum.

analyser dispersion

The term analyser dispersion is usually applied to optical spectrometers. It represents quotient of the change in position, Dx, of the radiation or the dispersed particles at the exit of the spectrometer by the change in wavelength, Dl. When the dispersion is expressed in angles rather than in position this is should be specified by using angular dispersion.

b

 

BEC

background equivalent concentration, i.e. the concentration that corresponds to background signal

c

 

CDP

During Compositional Depth Profiling the chemical or atomic composition or a generally solid material is determined as a function of depth i.e. the distance from the normal to the surface.

CRM

certified reference material

d

 

density

mass per unit volume, e.g. kg.m-3. A value easy to remember is the density of water : 1g.cm-3

depth profiling

the monitoring of signals versus time during sputtering of a surface

e

 

emission yield

The term emission yield is frequently used in GDOES. It is defined as quotient of time-integrated optical emission signal after background substraction at a specified wavelength by the mass of the emitting element sputtered in the time interval of interest.

f

 

g

 

GD-MS

Glow Discharge Mass Spectrometry, glow discharge mass spectrometry is an analytical 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. The method can be used for the determination of elemental composition of both homogeneous solid bulk material as well as surfaces.

GD-OES

Glow Discharge Optical Emission Spectrometry

glow discharge

the luminous effect of passing current through a gas, with a large potential difference (voltage) between the electrodes. Check the our glow-dicharge.com web-site for more inormation

h

 

i

 

ICP

Inductively coupled plasma

inductively coupled

power provided by magnetic induction

j-l

 

m

 

magnetic induction

the effect of passing alternating current through a coil

monochromator

a spectrometer which records signals at one wavelength at a time. For more information check our monchromators page!

n

 

o

 

oscillator strength

number of electrons in a level available for excitation

OES

optical emission spectrometry

optical emission

the release of photons by atoms

p

 

photoelectric effect

The photo effect is the interaction of a photon with bound electrons in atoms, molecules, and solids, resulting in the production of one or more emission "free" photoelectrons. The short term "photo effect" is also used for this process;

photon

a small packet of electro-magnetic energy

plasma

a gas containing electrons and ions

polychromator

a spectrometer which records signals at many wavelengths simultaneously. For more information check our polychromator page

precision

Closeness of agreement between independant test results obtained under defined conditions. Different to accuracy and trueness, the precision depends only on distribution on random errors and makes no reference to an accepted reference value. Precision is usually expressed as imprecission, the standard deviation of the test results. A larger standard deviation means less precision. The precision derived from a set of test results depends stongly on the stipulated conditions. Whether one or several operators have performed the tests on one or several instruments in one or several laboratory etc. will certainly influence the precision derived from the obtained test results.

q

 

quantitative depth profiling

the determination of concentration versus depth

r

 

RM

reference material

repeatability

closeness of agreement between results using the same material over 1-2 days

reproducibility

closeness of agreement between results measured in different laboratories using the same material

reproducibility, within-laboratory

closeness of agreement between results using the same material but measured long-term after recalibration

resolution of a spectrometer

The resolution of a spectrometer, energy, mass or optical, is the contribution of the spectrometer to the measured full width at half maximum (FWHM) intensities of spectral peaks above their local backgrounds. (Care should be taken with this definition as others are commonly used)
The relative resolution is the ratio of the resolution of a spectrometer at a given energy, mass or wavelength to that energy, mass or wavelength. A different term, sometimes used is percentage.spectrometer dispersion.
The resolving power of a spectrometer is the reciprocal of the relative resolution of a spectrometer. In practice, the spectrometer resolution, relative resolution or resolving power can be deduced using a source with an emission line, or other relevant feature, of known width, usually chosen to be narrow in comparison to the resolution of the spectrometer to be tested..
Which term is more useful depends on the design of spectrometer. Some spectrometer maintain the resolution constant throughout the spectrum. For others the resolution may be proportional to the measured quantity, energy, mass or wavelength. For the former, the resolution is a useful term whereas, for the latter, the relative resolution and resolving power. However, for many spectrometer designs neither case is true. In most optical spectrometers using a grating as dispersion element, such as Paschen-Runge and Cerny-Tuner, neither the relative nor the absolute is constant over large parts of the spectrum. In the case time of flight mass spectrometers (ToFMS) the resolution in the time domain may be constant but this implies it that neither the resolution nor the relative mass resolution is constant over a large mass range. When expressing the resolving power of such instrument the value of the measured quantity for which the give value applies should be specified.

s

 

self-absorption

re-absorption of light emitted by atoms or ions, by other like atoms or ions

SIMS

secondary-ion mass spectrometry is 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 energetic ions. SIMS is by conventions split into two different branches dynamic and static SIMS.In dynamic SIMS the material surface layers are continually removed as they are being measured. In static SIMS the ion areic dose during measurement is restricted to less than 1016 ions/m2 in order to keep the surface essentially undamaged.

SNMS

sputtered neutral mass spectrometry, or SNMS, is 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. The neutral species may be detected by using different ionisisation methods as plasma, electron, or photon ionisation.

spark

the luminous effect of a high current discharge

spectrometer

an instrument for separating and recording signals at different wavelengths

spectrometry

measurement of spectra

spectrometer response and transmission function

The spectrometer transmission function is quotient of the number of particles transmitted by the analyser by the number of such particles per solid angle and per interval of the dispersing parameter (e.g. energy, mass or wavelength) available for measurement as a function of the dispersing parameter, again energy, mass or wavelength. The transmission function should not be confused with the solid angle of acceptance. The transmission may be expressed in unit of sr.eV, sr.amu or sr.m.
The spectrometer response function, in contrary to the transmission function, also includes the detection and signal recording processes. It is the quotient of the number of particles detected with a spectrometer by the number of such particles per solid angle and per interval of the dispersing parameter available for measurement as a function of the dispersing parameter.
The spectrometer étendue includes, in addition to the transmission function, the influence of the analysis area on the transmission. The étendue is the surface integral of the product of the spectrometer transmission and a surface element, normal to the analyser axis passing through the centre of the analysis area, divided by that integral surface. A plane surface should be chosen as surface the integral.

spectroscopist

anyone working in spectroscopy, using spectroscopic instruments, or who has made a significant contribution to spectroscopy.

spectroscopy

study of spectra

sputtering

Sputtering is the process in which atoms and ions are ejected from the sample as a result of particle bombardment. The sputtering rate is quotient of the amount of sample material removed, as a result of particle bombardment, by time. This rate may be measured as a velocity, a mass per unit area per unit time, or some other measure of quantity per unit time. The sputtering yield describes ratio of the number of atoms and ions sputtered from a sample to the total number of incident primary particles
The erosion rate of a surface is understood as quotient of the change in the position of the surface as a result of particle or photon irradiation by the time of irradiation It can be deduced from surface profilometer measurements of a crater after analysis. In this case, the effects of the altered layer and post-profile oxidation need to be considered. Where the erosion is caused by sputtering, it may initially differ from the sputtering rate as a result of the retention of sputtering particles.
The crater may be different from the thickness of sample material removed by sputtering due to dilation of the altered layer. Additionally it may be modified by the formation of a reacted layer, typically an oxide layer, following any exposure to the atmosphere or other environments.
The sputtering rate, different from the erosion rate is to be understood as quotient of the amount of sample material removed, as a result of particle bombardment, by time
The bombardment of the sample surface with energetic ions and atoms during the sputtering process the composition and microscopic structure of the outermost atomic layer may be altered through recoil implantation, also known as knock-on and knock-in effect. This effect of this movement of sample atoms deeper into the sample is generally called atomic mixing, cascade mixing or a collision cascade. The knock-on refers to the forward movement of the atoms, whereas cascade mixing includes a more general movement of the atoms.
Sputter techniques show more or less significant preferential sputtering when multicomponent material is sputtered. The means that elements present at the sample surface are not sputtered at the same rate. In this case a change in the equilibrium surface composition of the sample may occur. After 'some' time of sputtering a steady-state surface composition produced by sputtering non-varying conditions. Providing the sample is sufficiently homogeneous.
As crater depth we understand the average depth of the region of a crater from which the measured signal is derived. It is therefore not necessarily equal to the average depth of the sputtered crater. Signals may be collected preferentially from the crater centre or the signal collection process may include the crater edge, which is often shallower the central region. In the later case we speak about the crater edge effect.

sputtering rate

mass removed by sputtering per unit time, read more: sputtering

SRM®

standard reference material, registered trade mark of NIST

standard

nationally or internationally agreed written procedure; note: reference materials are often informally called standards, leading to some confusion

surface

the region of a sample which builds the interphase between the condesed phase (liquid or solid) and a gas phase. Where the gas phase can in particular be understood as vapour or vacuum.

T

 

ToF

Time of Flight Mass Spectrometry. Ions of different mass but the same kinetic energy will have different speed. This fact is used for mass speperation in TOF MS

tracability

demonstrated, unbroken chain of the measurement results to National or International standards

trueness

Trueness expresses how well the average of a large series of test results agrees with an accepted reference value. Trueness is usually expressed as bias, the difference between the average of the test resuits an the accepted reference value.

TXRF

For Total reflection X-Ray Fluorescence spectroscopy, or TXRF, 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

u

 

uncertainty

measure of the dispersion (variation) of measured values

v

 

w

 

wavelength

the distance between two equivalent points in a wave; for light measured in nm (nanometres)

x-z