Reflectometric study of contaminant layer on a probe window

Area of Science:

• Materials Science
• Optical Physics
• Chemical Engineering

Background:

• Contamination on optical surfaces can affect instrument performance.
• Pulping solutions containing lignin are a potential source of such contaminants.
• Understanding contaminant properties is crucial for maintaining reflectometer accuracy.

Purpose of the Study:

• To investigate the properties of a lignin-based contaminant layer on a probe window (prism).
• To determine the refractive index (n), extinction coefficient (k), and effective thickness (d) of the contaminant.
• To analyze the growth rate of the contaminant layer over time.

Main Methods:

• Utilized a reflectometer apparatus with a probe window (prism).
• Developed an optical model assuming a continuous, homogenous contaminant layer with an inter-diffusion layer.
• Employed depth profiling and optical modeling for data fitting.
• Experimentally varied contact time up to 5.0 hours and light source wavelengths (300, 400, 500 nm).

Main Results:

• The contaminant layer's optical properties (n, k, d) were determined using the proposed optical model.
• The growth rate of the contaminant layer was found to be approximately 60 nm per hour.
• Experimental results showed consistency for both s- and p-polarizations across different wavelengths.

Conclusions:

• The optical model effectively characterized the lignin contaminant layer on the probe window.
• The determined growth rate provides valuable data for predicting and managing contamination.
• The findings support the reliability of reflectometer measurements despite potential contamination.