XPS depth profiling of nano-layers by a novel trial-and-error evaluation procedure

Area of Science:

• Materials Science
• Surface Analysis
• Nanotechnology

Background:

• X-ray Photoelectron Spectroscopy (XPS) depth profiling offers high chemical sensitivity but is limited by sputter-induced alterations and challenges in analyzing thin layers (2-3 inelastic mean free paths - IMFP).
• These limitations lead to inhomogeneous in-depth concentration distributions, hindering reliable material analysis.

Purpose of the Study:

• To demonstrate the applicability of XPS depth profiling even in unfavorable cases involving thin layers.
• To present a method for overcoming the limitations of XPS depth profiling for analyzing nano-layers.

Main Methods:

• XPS depth profiling of a model system: a tungsten-carbide-rich nano-layer.
• Correction of issues related to photoelectron IMFP by introducing a layer model for XPS intensity calculations.
• Handling sputter-induced alterations (ion mixing, compound formation) using TRIDYN simulations.

Main Results:

• The developed method successfully corrects for challenges posed by long photoelectron IMFP in thin layers.
• TRIDYN simulations effectively managed sputter-induced artefacts, ensuring data integrity.
• Accurate depth profiling was achieved for a hard, corrosion-resistant tungsten-carbide nano-layer.

Conclusions:

• The presented approach overcomes the inherent limitations of XPS depth profiling, particularly for thin layers.
• This method enhances the reliability and applicability of XPS for analyzing complex nano-structured materials.
• The study validates XPS depth profiling as a viable technique for materials with high hardness and corrosion resistance.