ISO 23420:2021

Overview

ISO 23420:2021 defines a standardized procedure to determine the energy resolution of electron energy loss spectroscopy (EELS) systems installed on scanning/transmission electron microscopes (S/TEM or TEM). It applies to both in‑column and post‑column EEL spectrometers and to parallel and serial detection systems. The standard establishes how to calibrate energy steps, measure the zero‑loss peak (ZLP), and calculate the spectrometer energy resolution (ΔE) for reliable EELS analysis.

Key Topics and Requirements

• Scope & applicability: Measurement method for energy resolution in S/TEMs equipped with EEL spectrometers (in‑column and post‑column; parallel and serial detection).
• Definitions & symbols: Clarifies terms such as zero‑loss peak (ZLP), energy step (δE), energy dispersion, FWHM, collection angle, and channels used in parallel detection.
• Reference materials & calibration:
  • Use of graphite reference and measurement of the graphite C1s binding energy by XPS (X‑ray photoelectron spectroscopy) to align energy scales.
  • Selection of reference materials for energy‑scale calibration and correspondence between XPS C1s and EELS carbon K edge (covered in informative Annex B).
• Measurement procedure:
  • Predetermination of binding energies, setup of S/TEM and EELS, and sample mounting.
  • First and second energy step (δE) calibrations using graphite/plasmon and other reference peaks.
  • Acquisition of carbon K‑edge and low‑loss spectra, locating peaks close to ZLP, and measuring channel distances (CH) on calibrated δE.
  • Determination of ΔE from the FWHM of the zero‑loss peak on the calibrated energy scale.
• Uncertainty: Guidance on evaluating measurement uncertainty (reference to GUM principles).
• Supporting material: Annex A provides an example measurement procedure.

Applications and Who Uses It

• Materials scientists and microscopists performing quantitative EELS for composition, bonding and electronic-structure analysis.
• Electron microscopy facilities and core labs implementing quality control and routine instrument characterization.
• Instrument manufacturers validating EELS performance and delivering calibrated systems.
• Calibration and testing labs, and standards bodies seeking repeatable, comparable ΔE measurements across instruments.
• Practical use cases include plasmon and core‑loss peak decomposition, energy-shift studies, and any EELS workflow where accurate energy resolution is critical.

Related Standards

• ISO 15932 (referenced for zero‑loss definition)
• GUM (Guide to the Expression of Uncertainty in Measurement) principles for uncertainty evaluation

Keywords: ISO 23420:2021, energy resolution, EELS, electron energy loss spectroscopy, S/TEM, zero‑loss peak, δE calibration, graphite C1s, XPS calibration, ΔE determination.