ISO 13084:2025

International
Standard
ISO 13084
Third edition
Surface chemical analysis — Mass
2025-10
spectrometries — Calibration of
the mass scale for a time-of-flight
secondary ion mass spectrometer
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 1
4.1 Symbols .1
4.2 Abbreviated terms .2
5 Outline of method . 2
6 Method for improving mass accuracy . 3
6.1 Obtaining the reference sample for optimization .3
6.2 Preparation of polycarbonate sample.3
6.3 Obtaining the SIMS spectral data .4
6.4 Calculating mass accuracy .4
6.5 Optimizing instrumental parameters .7
6.6 Calibration procedure .8
Annex A (informative) Calibration uncertainty . 10
Annex B (informative) Internal addition method .11
Bibliography .13

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 201, Surface chemical analysis, Subcommittee
SC 6, Mass spectrometries.
This third edition cancels and replaces the second edition (ISO 13084:2018), which has been technically
revised.
The main changes are as follows:
— addition of informative Annex B.
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.

iv
Introduction
Secondary ion mass spectrometry (SIMS) is a powerful technique for the analysis of organic and molecular
surfaces. Over the last decade, instrumentation has improved significantly so that modern instruments
[2]
now have very high repeatability and constancy . A growing need is for the identification of the chemical
composition of complex molecules from accurate measurements of the mass of the secondary ions. The
relative mass accuracy to do this and to distinguish between molecules that contain different chemical
constituents, but are of the same nominal mass (rounded to the nearest integer mass), is thus an important
parameter. A relative mass accuracy of better than 10 ppm is required to distinguish between C H
2 4
(28,031 30 u) and Si (27,976 92 u) in a parent ion with total mass up to 1 000 u, and between CH (14,015 65 u)
and N (14,003 07 u) in parent ions with total mass up to 300 u. However, in a recent interlaboratory
[3]
study , the average fractional mass accuracy was found to be 150 ppm, which is significantly worse than
[4]
the accuracy needed for unambiguous identification of ions. A detailed study shows that the key factors
degrading the accuracy include the large kinetic energy distribution of secondary ions, non-optimized
instrument parameters and extrapolation of the mass scale calibration.
This document describes a simple method, using locally sourced material, to optimize the instrumental
parameters, as well as a procedure to ensure that accurate calibration of the mass scale is achieved within a
selectable uncertainty.
v
International Standard ISO 13084:2025(en)
Surface chemical analysis — Mass spectrometries —
Calibration of the mass scale for a time-of-flight secondary
ion mass spectrometer
1 Scope
This document specifies a method to optimize the mass calibration accuracy in time-of-flight secondary
ion mass spectrometry (SIMS) instruments used for general analytical purposes. This document is only
applicable to time-of-flight instruments but is not restricted to any particular instrument design. This
document gives guidance for some of the instrumental parameters that can be optimized using this
procedure and the types of generic peaks suitable to calibrate the mass scale for optimum mass accuracy.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Symbols and abbreviated terms
4.1 Symbols
m mass of interest
m calibration mass 1
m calibration mass 2
M mass (u)
M peak centre (u)
ΔM mass accuracy (u)
M measured peak mass (u)
P
M true mass (u)
T
U(m) mass uncertainty for a mass, m, arising from calibration
U uncertainty in the accurate mass measurement of m
1 1
U uncertainty in the accurate mass measurement of m
2 2
U average uncertainty in an accurate mass measurement
V reflector or acceptance voltage (V)
R
W relative mass accuracy
x number of carbon atoms
y number of hydrogen atoms
G scaling term
α asymmetry term
σ(ΔM) standard deviation of the mass accuracy for a number of peaks
+
σ average of the standard deviations of ΔM for each of the four C H cascades with 4, 6, 7 and 8 car-
M x y
bon atoms
4.2 Abbreviated terms
MEMS micro-electromechanical system
PC polycarbonate
ppm parts per million
r/min revolutions per minute
SIMS secondary ion mass spectrometry
THF tetrahydrofuran
ToF time-of-flight
5 Outline of method
Here, the method is outlined so that the detailed procedure, given in Clause 6, can be understood in
context. First, to optimize a time-of-flight mass spectrometer using this procedure, obtain a thin film of
polycarbonate (PC) on a conducting substrate (silicon). The optimization procedure is achieved by carrying
out the procedures in 6.3 to 6.5 iteratively; it uses 19 specific C H peaks in the PC positive-ion mass
x y
spectrum. In 6.6, a general calibration procedure is given which provides the rules by which calibrations
for inorganics and organics may be incorporated. This leads to a new generic set of ions for mass calibration
that can improve the mass accuracy from some often-used calibrations by a factor of five. The effects of
extrapolation beyond the calibration range are discussed and a recommended procedure is given to
ensure that accurate mass is achieved, within a selectable uncertainty, for large molecules. Therefore, the
procedure has two parts, optimization and calibration. Subclauses 6.1 to 6.5 are only required as part of the
regular maintenance of the instrument as defined by the testing laboratory. Subclause 6.6 is required for all
calibrations of the mass scale. This is summarized in the flowchart in Figure 1.

Figure 1 — Flowchart of sequence of operations of the method
6 Method for improving mass accuracy
6.1 Obtaining the reference sample for optimization
A sample of thin (10 nm to 100 nm) PC on a flat conducting substrate (e.g. silicon wafer) shall either be
obtained or prepared, as described in 6.2.
6.2 Preparation of polycarbonate sample
6.2.1 Instructions for the preparation of a PC reference sample are provided. This method can give sample-
[2]
to-sample repeatability in ToF SIMS spectra of better than 1,9 % . To prepare such a sample for static SIMS
analysis requires a clean working environment. To reduce surface contamination, clean glassware, tweezers
and powderless gloves shall be used. The equipment required is a 1 ml glass pipette, a 100 ml glass-stoppered
measuring flask and a device for spin casting. If a device for spin casting is not available, droplet deposition
of the PC solution may be used. However, this will give poor repeatability, which will need to be carefully
taken into account during spectral analysis.
6.2.2 Using poly(bisphenol A carbonate), abbreviated to PC, weigh out 100 mg on a clean piece of
aluminium foil. Introduce the PC into the 100 ml, glass-stoppered measuring flask, add tetrahydrofuran
(THF) of analytical reagent quality to the 100 ml level line. Shake the flask to mix the PC and allow time to
dissolve it completely. This produces a 1 mg/ml solution of PC in THF. The aluminium foil shall be freshly
unrolled and the shiny surface used. Ensure that the THF is anhydrous, otherwise streaks will appear from
water when spin coating, as described in 6.2.3. The shelf life of freshly prepared stock solution shall be no
more than one month owing to water take-up.
...