XPS Principle
X-ray Photoelectron Spectroscopy (XPS) is based on the principle of photoionization. When a beam of photons irradiates the sample surface, the photons can be absorbed by electrons in the atomic orbitals of an element in the sample, causing the electrons to escape the nucleus's binding and emit from the atom with a certain kinetic energy as free photoelectrons, while the atom itself becomes an excited-state ion. When the excitation source energy is fixed, the energy of photoelectrons depends only on the element type and the ionized atomic orbital, enabling qualitative analysis of elemental composition based on photoelectron binding energy. The intensity of photoelectrons emitted from the sample surface after X-ray irradiation is linearly related to the atomic concentration in the sample, allowing semi-quantitative elemental analysis. Additionally, an important application of XPS is the analysis of elemental chemical valence states.
Instrument Model and Technical Parameters
- Instrument Model: Thermo Scientific K-Alpha
- Technical Parameters:
- Ion source: 100–4000 eV
- Beam spot diameter: 1–10 mm
- Sputtering rate range: 0.1–50 nm/min
- Sampling depth: Metal 0.5–2 nm, inorganic materials 1–3 nm, organic materials 3–10 nm
Sample Submission Requirements and Notes
- Solid powder: Uniform and dry, particle size < 70 μm (passed through 200-mesh sieve), mass ≥ 100 mg.
- Bulk, metal, and film samples: Length and width < 10 mm, height < 5 mm.
- Samples with volatile components or oily contaminants must be pre-cleaned.
- Magnetic samples must be declared in advance to avoid equipment damage.
Testing Examples
Reference Standards
- ISO 15472:2001 "Surface chemical analysis - X-ray photoelectron spectroscopy - Determination of measurement repeatability and reproducibility"
- ISO 15473:2001 "Surface chemical analysis - X-ray photoelectron spectroscopy - Methods for spectrum identification and peak fitting"
- ISO 17808:2014 "Surface chemical analysis - X-ray photoelectron spectroscopy - Guide to Auger parameter and chemical state analysis"
- ASTM D5709-95 (2015) "Standard Practice for Analysis of Organic Polymer Surfaces by X-ray Photoelectron Spectroscopy"
- ASTM E1509-11 (2019) "Standard Guide for Surface Analysis by X-ray Photoelectron Spectroscopy"
- ASTM E1621-14 (2020) "Standard Test Method for Chemical Analysis of Materials by X-ray Photoelectron Spectroscopy"
