ISO 18114:2021 Surface chemical analysis — Secondary-ion mass spectrometry — Determination of relative sensitivity factors from ion-implanted reference materials

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Surface chemical analysis — Secondary-ion mass spectrometry — Determination of relative sensitivity factors from ion-implanted reference materials由ISO于2021-05-11发布，适用于世界范围。

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INTERNATIONAL STANDARD ISO 18114:2021

Surface chemical analysis — Secondary-ion mass spectrometry — Determination of relative sensitivity factors from ion-implanted reference materials

1 Scope

This document specifies a method of determining relative sensitivity factors (RSFs) for secondary-ion mass spectrometry (SIMS) from ion-implanted reference materials.

The method is applicable to specimens in which the matrix is of uniform chemical composition, and in which the peak concentration of the implanted species does not exceed one atomic percent.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 18115 (all parts), Surface chemical analysis — Vocabulary

3 Terms a nd definiti ons

For the purposes of this document, the terms and definitions given in ISO 18115 (all parts) apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https://www.iso.org/obp

— IEC Electropedia: available at http://www.electropedia.org/

4 Symbols and abbreviated terms

atomic concentration of the analyte element A in the matrix M at cycle i of a depth profile, AM,

C

i

expressed in atoms per unit volume

d depth over which the depth profile is integrated, expressed in length units

detected count rates of the analyte ion of isotope A at measurement cycle i, expressed in A

j

j

I

i counts per second

detected count rates of the reference isotope M at measurement cycle i, expressed in counts M

k

k

I

i

per second

I mean background count rate of species A , expressed in counts per second

BG j

Aj

N fractional isotopic abundance of the analyte isotope A in the unknown sample

j

n number of cycles over which the depth profile is integrated

Φ implanted fluence of isotope A , expressed in atoms per unit area

j

RSF relative sensitivity factor, expressed in atoms per unit volume

ISO 18114:2021

SIMS secondary-ion mass spectrometry

5 Principle

An isotopic relative sensitivity factor (RSF) for a particular element-matrix combination is derived from a SIMS depth profile of an ion-implanted external standard. This RSF can then be used to quantify the concentration of the same element as a function of depth in a different sample of the same matrix material, using Formula (1):

A

AM,

 j 

jk

RSF ×−II

 

i BG

AM,  

C = (1)

i

M

A

k

j

IN×

i

This procedure only applies to samples and reference materials in which the detected count rate of the analyte ion is directly proportional to its concentration. Causes of divergence from the proportionality are matrix effect when analyte concentration is too high, or detector saturation when the single ion counter is used as the detector system. In practice, to avoid divergence from the proportionality caused by matrix effect, the upper limit of analyte concentration is generally assumed to be one atomic percent. When the cause of divergence from the proportionality is only the detector saturation and when detected intensity can be corrected according to ISO 20411, this procedure can apply after intensity correction. The measurement conditions used for the analysis of reference materials and unknown samples shall be the same.

M

k

NOTE 1 As for I in Formula (1), the signal is much higher than the background, so the background is i

negligible. Formula (1) solves for elemental concentration.

NOTE 2 As far as matrix effect concerned, one atomic percent is acceptable for most case, but some cases it is not. For example, an addition of 1 % potassium to a metal catalyst does change the electronic structure of the entire metal phase such that influences on the chemical reactivity and the RSF can be expected.

6 Apparatus

The procedure described here can be used to determine an RSF from data obtained with any SIMS instrument that is capable of obtaining depth profiles. Follow the instrument manufacturer's instructions or local documented procedures for setting up the instrument to obtain the best quality depth profile data.

7 Ion-implanted reference materials

Ion-implanted reference materials for this procedure shall have peak concentrations below one atomic percent, but at least a factor of 100 greater than the background intensity or detection limit of the analyte element in the SIMS instrument. The depth of the peak in the depth distribution of the analyte shall be at least a factor of two below the depth of the onset of steady-state sputtering conditions as indicated by the stability of a matrix reference signal. Use certified reference materials (CRMs) or secondary materials derived from CRMs, when available. If no CRM is available, use reference materials for which the implanted fluence has been measured by an independent method such as Rutherford backscattering spectrometry or neutron activation analysis, if possible.

8 Procedure

A

M

j

k

Determine the count rates of the ions of analyte isotope A , I , and reference isotope M , I , at each j k

i i

measurement cycle i of the depth profile of the implanted reference material. Calculate the relative sensitivity factor for isotopic species A of element A in matrix M with isotopic reference species M j k

from Formula (2):

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