Overview
ISO/TS 22933:2022 - "Surface chemical analysis - Secondary ion mass spectrometry - Method for the measurement of mass resolution in SIMS" is a technical specification from ISO/TC 201/SC 6. It defines how to measure and report mass resolution in secondary ion mass spectrometry (SIMS) and how to compare mass resolution across different SIMS instrument types (TOF‑SIMS, Magnetic‑SIMS, Quadrupole‑SIMS, Orbitrap‑SIMS, FTICR‑SIMS, etc.). The document emphasizes reporting the peak shape and the exact method used to determine ΔM (mass separation) or resolving power R = M/ΔM.
Key topics and requirements
- Definitions of mass resolution: Several practical definitions are given and compared, including
- X% valley between two equal peaks,
- X% peak width (e.g., FWHM at 50%, or widths at 10%, 1%),
- X% peak‑tail interference (abundance sensitivity / tail contribution).
- Symbols and terminology: Standardized terms and abbreviations (ΔM, M/ΔM, X% valley, TOF‑SIMS, M‑SIMS, Q‑SIMS, FT‑SIMS, etc.) aligned with ISO vocabulary (see ISO 18115‑1).
- Measurement procedure: Practical measurement guidance including
- removing surface contamination (sputtering or equivalent),
- acquiring peaks from a clean measurement area (away from edges),
- adjusting primary beam and detector to keep signals in the detector linear range,
- ensuring adequate signal (examples: SNR and counts thresholds are specified),
- reporting the measured peak shape together with the chosen ΔM/R definition.
- Instrument comparisons: Methods to compare mass resolution across instrument types are described, with examples and considerations for TOF, magnetic sector, quadrupole and Fourier‑transform based SIMS.
Applications and users
ISO/TS 22933:2022 is valuable for:
- SIMS instrument manufacturers - to support consistent, comparable performance claims.
- Surface analysis laboratories - to set acceptance criteria, optimize instrument settings, and document analytical capability.
- Materials scientists, geochemists, semiconductor analysts - when choosing SIMS techniques for isotope ratio work, trace element detection, or resolving isobaric interferences.
- Metrology and QA teams - for instrument qualification, routine checks and inter‑laboratory comparisons.
Practical benefits include clearer specification of resolving power requirements for a given analysis, improved comparability between TOF‑SIMS, Magnetic‑SIMS, Q‑SIMS and FT‑based SIMS, and reduced risk of false positives/negatives caused by inadequate mass resolution.
Related standards
- ISO 18115‑1 (Surface chemical analysis - Vocabulary) is cited for terminology.
- Prepared by ISO/TC 201 (Surface chemical analysis), Subcommittee SC 6 (SIMS).