Characterizing the Intrinsic Background in XPS Using the Narrow-Shirley Approach.

Area of Science:

• Materials Science
• Surface Science
• Spectroscopy

Background:

• X-ray Photoelectron Spectroscopy (XPS) background signals have extrinsic and intrinsic components.
• Characterizing the intrinsic background across extended binding energy (BE) ranges is crucial.
• Existing Shirley algorithm for near-peak analysis fails in extended regions.

Purpose of the Study:

• To characterize the structure of the intrinsic background in XPS across an extended BE range.
• To develop a modified background analysis method suitable for extended energy regions.
• To explore the physical origin of the intrinsic background structure.

Main Methods:

• Application of the empirical Shirley algorithm for near-peak intrinsic background.
• Development and application of a modified Shirley algorithm (narrow-Shirley or NS background) for extended BE ranges.
• Comparison of intrinsic background structure with Auger Electron Spectroscopy (AES) and X-ray Absorption Spectroscopy (XAS) data.
• Synchrotron experiments to test photon energy dependence of the intrinsic background.

Main Results:

• The intrinsic background in extended BE regions can be modeled by wide Gaussian peaks.
• The narrow-Shirley (NS) background method successfully reproduces experimental data and reveals underlying structure.
• The ICVBL mechanism is proposed as the origin of the entire intrinsic background structure.
• Experimental validation of ICVBL predictions using AES, XAS, and synchrotron data.

Conclusions:

• The narrow-Shirley (NS) background method accurately characterizes intrinsic XPS signals across extended binding energy ranges.
• Interchannel Coupling with Valence Band Losses (ICVBL) is identified as the mechanism responsible for the entire intrinsic background structure.
• This work provides a robust method for background analysis in XPS and insights into electronic structure.