Overview
ISO/TS 25138:2025 - Surface chemical analysis - Analysis of metal oxide films by glow discharge optical emission spectrometry (GD-OES) - specifies a GD‑OES method for measuring the thickness, mass per unit area, and chemical composition of metal oxide films. The method covers oxide layers from 5 nm to 10 000 nm on metallic substrates and supports determination of metallic constituents (e.g., Fe, Cr, Ni, Cu, Ti, Si, Mo, Zn, Mg, Mn, Zr, Al) and non‑metals (O, C, N, H, P, S).
Key topics and technical requirements
ISO/TS 25138:2025 provides practical guidance and requirements across the GD‑OES workflow:
- Principle and apparatus: overview of glow discharge optical emission spectrometers, selection of spectral lines and glow discharge source types (DC and RF).
- Instrument settings: recommended procedures for adjusting discharge parameters (constant current/voltage/power modes), detector sensitivity, and accommodating array detectors.
- Performance checks: minimum performance requirements including repeatability, detection limits, lamp cleanliness and start‑up behavior.
- Sampling and sample preparation: requirements to ensure vacuum sealing and representative analysis.
- Calibration and validation: use of calibration and validation samples, determination of sputtering rates, emission intensity measurement, calibration formulae and verification/drift correction.
- Analysis and reporting: procedures for acquiring depth profiles, calculating oxide mass per unit area, average oxide composition, precision assessment and required test report content.
- Annexes: informative guidance on calibration calculations, suggested spectral lines, oxide density examples and interlaboratory test reports.
Notable updates in the 2025 third edition include added support for array detectors, an additional anode size (2.5 mm), clarified vacuum seal checks, revised optical system checks for array systems, and making crater‑shape optimization optional.
Applications and users
ISO/TS 25138:2025 is intended for professionals performing surface chemical analysis and thin film characterization using GD‑OES, including:
- Materials scientists and metallurgists studying oxide scale and corrosion layers
- Quality control and R&D labs in automotive, aerospace and electronics industries
- Coatings and surface‑treatment laboratories (anodizing, passivation, thermal oxidation)
- Semiconductor and microelectronics engineers concerned with native and grown oxide films
The standard enables repeatable, comparable measurements of oxide thickness and composition for process control, failure analysis, and research.
Related standards
- ISO 14707 - Glow discharge optical emission spectrometry (GD‑OES) - Introduction to use
- ISO 14284 - Steel and iron - Sampling and preparation for chemical composition determination
Keywords: ISO/TS 25138:2025, GD‑OES, glow discharge optical emission spectrometry, metal oxide films, surface chemical analysis, oxide thickness, composition, calibration.