Overview
ISO 13084:2025 - Surface chemical analysis - Mass spectrometries - Calibration of the mass scale for a time‑of‑flight secondary ion mass spectrometer (ToF‑SIMS) - specifies a practical method to optimize mass calibration accuracy for ToF‑SIMS instruments used in general analytical work. The standard is instrument‑design agnostic (applies only to ToF instruments) and provides guidance on sample preparation, spectral data acquisition, peak fitting, iterative optimization of instrumental parameters, and calibration procedures to achieve improved relative mass accuracy (reported in ppm).
Keywords: ISO 13084:2025, ToF‑SIMS calibration, mass accuracy, mass spectrometry calibration, surface chemical analysis.
Key technical topics and requirements
- Scope and approach
- Focused on improving mass scale calibration and reducing mass errors that arise from kinetic energy distributions, non‑optimized instrument parameters, and extrapolation beyond calibration ranges.
- Reference sample and sample prep
- Uses a thin polycarbonate (PC) film on a conducting substrate (e.g., silicon) as a readily available reference. Typical film thickness guidance: 10 nm to 100 nm; recommended PC solution preparation and spin‑casting steps are provided.
- Data acquisition
- Guidance on ToF instrument settings to obtain spectra suitable for calibration, including recommended acquisition time and counts to ensure quality spectra.
- Peak fitting and mass accuracy calculation
- Uses an asymmetric Gaussian fit to determine peak centers (recommended to fit intensities above 50% of the peak maximum to avoid neighbouring interference).
- Defines mass accuracy ΔM (difference between measured peak center and true mass) and relative mass accuracy W (expressed in ppm).
- Optimization and calibration procedure
- Iterative optimization using a set of specific hydrocarbon peaks from PC (19 peaks) to tune instrumental parameters for best mass accuracy, followed by a general calibration procedure for organics and inorganics.
- Uncertainty and annexes
- Informative Annex A addresses calibration uncertainty; Annex B describes an internal addition method for calibration enhancement.
Practical applications and users
- Target users:
- Surface analysts, materials scientists, forensic labs, semiconductor/metrology labs, ToF‑SIMS instrument manufacturers, and calibration/quality assurance laboratories.
- Practical benefits:
- Improves confidence in molecular identification from ToF‑SIMS spectra, enabling discrimination of isobaric species (e.g., CHx vs N or Si), supports routine instrument maintenance, and reduces interlaboratory variability in mass accuracy.
Related standards
- ISO 23830 (referenced for high‑quality SIMS spectral acquisition practices)
- ISO technical committee: ISO/TC 201, Surface chemical analysis (Subcommittee SC 6: Mass spectrometries)
ISO 13084:2025 is a practical, implementable standard to raise ToF‑SIMS mass calibration performance and to provide traceable, uncertainty‑aware mass measurements for surface chemical analysis.