Surface-Sensitive XAFS in the Hard X-ray Region with Sub-Monolayer Sensitivity

Area of Science:

• Materials Science
• Surface Science
• Solid-State Physics

Background:

• Surface analysis requires techniques with high sensitivity to probe atomic-level structures.
• X-ray absorption fine structure (XAFS) is a powerful tool for elemental and structural analysis.
• Existing XAFS methods often lack the necessary sensitivity for sub-monolayer surface studies.

Purpose of the Study:

• To develop and demonstrate a highly surface-sensitive X-ray absorption fine structure (XAFS) technique.
• To enhance fluorescence detection efficiency for improved XAFS measurements.
• To apply the technique for structural characterization of surfaces and buried interfaces.

Main Methods:

• Utilized grazing-incidence fluorescence detection for surface sensitivity.
• Combined a multipole wiggler with a multi-element Si(Li) solid-state detector to boost fluorescence detection efficiency.
• Performed As K-edge XAFS studies on an InP(001) surface exposed to AsH(3).

Main Results:

• Achieved sub-monolayer sensitivity in surface XAFS measurements.
• Increased fluorescence detection efficiency by over two orders of magnitude.
• Demonstrated the incorporation of approximately 0.1 monolayer of As atoms into the InP(001) surface, substituting P atoms.

Conclusions:

• The developed grazing-incidence fluorescence XAFS technique offers exceptional surface sensitivity.
• This method is effective for structural studies of surfaces and interfaces in the hard X-ray region.
• The findings provide crucial insights into surface atomic substitution processes.