Soft X-ray absorption of thin films detected using substrate luminescence: a performance analysis

Area of Science:

• Materials Science
• Surface Science
• Spectroscopy

Background:

• X-ray absorption spectroscopy (XAS) is crucial for analyzing thin films across various scientific disciplines.
• Indirect detection methods are commonly employed for XAS, with X-ray excited optical luminescence (XEOL) being a notable technique.
• XEOL utilizes substrate luminescence as an effective transmission measurement, offering advantages for insulating samples and probing depths greater than 10 nm.

Purpose of the Study:

• To provide a systematic performance analysis of X-ray excited optical luminescence (XEOL) for thin film characterization.
• To establish guidelines for the effective utilization of XEOL, highlighting its advantages and limitations.
• To enable broader adoption of XEOL within the thin film research community.

Main Methods:

• Quantified the efficiency of XEOL across various commonly used substrates.
• Demonstrated the equivalence of XEOL and traditional X-ray transmission measurements for thin films.
• Applied X-ray magnetic circular dichroism (XMCD) sum rules to XEOL-generated data to showcase its utility in magnetic studies.

Main Results:

• Established the quantitative efficiency of XEOL for different substrates.
• Confirmed that XEOL measurements are equivalent to X-ray transmission measurements for thin films.
• Validated the application of XEOL in magnetic studies using XMCD sum rules.
• Identified and modeled a saturation-like effect in XEOL signals at greater film thicknesses.

Conclusions:

• XEOL is a powerful and versatile detection method for X-ray absorption spectroscopy of thin films.
• The study provides practical insights and validation for using XEOL, particularly for insulating materials and deeper probing.
• XEOL's applicability extends to magnetic characterization, and its signal saturation can be effectively managed.