ISO 24237:2005

Overview - ISO 24237:2005 (XPS intensity repeatability & constancy)

ISO 24237:2005 specifies a practical method to evaluate the repeatability and constancy of the intensity scale of X‑ray photoelectron spectrometers (XPS). The procedure applies to instruments using unmonochromated Al or Mg X‑rays or monochromated Al X‑rays and requires that the spectrometer incorporates an ion gun for sputter cleaning. ISO 24237 is not a full calibration of the instrument’s intensity/energy response function; instead it provides routine checks and data to confirm that the response function remains stable during instrument use.

Key topics and technical requirements

• Reference sample: Uses a high‑purity polycrystalline copper (Cu) foil as the standard sample for intensity checks.
• Sample preparation: Requires mounting with metallic contact, ultra‑high vacuum, and ion sputter cleaning to reduce carbon and oxygen contamination (criteria and example sputter procedures are provided in the standard).
• Measured peaks: Focuses on Cu 2p and Cu 3p photoelectron peaks to sample both high and low binding‑energy ends used in practical analyses.
• Repeatability testing: Specifies repeated measurements (sequence of measurements) to derive the repeatability standard deviation and measurement uncertainties.
• Constancy monitoring: Compares absolute intensities and intensity ratios over time to detect drift of the intensity/energy response function. Guidance is given on instrument settings (pass energy, retardation ratio, slits, lens settings, X‑ray source) that affect stability.
• Frequency and actions: Recommends regular assessments (example interval: every three months) and suggests remedial actions if drift is detected - improved sample positioning, longer warm‑up, resetting parameters, or recalibration by manufacturer/qualified body.

Practical applications

• Routine performance verification of XPS systems used in materials analysis, thin films, semiconductor processing, corrosion studies and surface chemistry.
• Supporting quality assurance (QA) in analytical labs by documenting instrument stability and estimating uncertainty in quantitative XPS results.
• Troubleshooting instrument drift to decide whether operational changes or manufacturer recalibration are needed.

Who should use this standard

• Surface analysis scientists and technicians operating XPS instruments.
• Laboratory quality managers who maintain measurement traceability and uncertainty budgets.
• Instrument manufacturers and service engineers who provide calibration and long‑term stability assessments.

Related standards

• ISO 15472 - XPS energy calibration (referenced for combined energy and intensity checks).

Keywords: ISO 24237:2005, X‑ray photoelectron spectroscopy, XPS, intensity scale, repeatability, constancy, Cu reference, ion sputter cleaning, intensity/energy response function.