Regimes of surface roughness measurable with light scattering

Area of Science:

• Surface science
• Optical metrology
• Materials science

Background:

• Light scattering is a key technique for analyzing surface topography.
• Understanding the relationship between scattered light and surface parameters is crucial for material characterization.

Purpose of the Study:

• To review and define regimes for measuring metallic surface roughness using light scattering.
• To establish approximate limits for each identified regime.

Main Methods:

• Analysis of previous experimental data on light scattering from metallic surfaces.
• Identification and characterization of different scattering regimes based on roughness parameters (σ/λ).

Main Results:

• Defined smooth-surface regime (0 < σ/λ ≲ 0.05) where scattered light relates to power spectral density.
• Identified regime for surface autocorrelation function calculation (0 < σ/λ ≲ 0.14).
• Established specular regime (0 < σ/λ ≲ 0.3) for specular beam measurement.
• Found rms width of scatter distribution is proportional to rms slope across regimes.

Conclusions:

• Light scattering provides a versatile method for quantifying metallic surface roughness.
• Distinct regimes allow for measurement of different surface properties, from microscopic details to overall slope.