Two-step regression procedure for the optical characterization of thin films

Area of Science:

• Materials Science
• Optical Physics

Background:

• Diamondlike carbon (DLC) films possess unique optical and electronic properties.
• Accurate characterization of DLC film parameters is crucial for device applications.
• Existing methods for optical characterization can be limited, especially with noisy data.

Purpose of the Study:

• To develop and validate a novel two-step regression procedure for analyzing DLC film reflectance spectra.
• To accurately determine key optical and physical parameters of DLC films.
• To compare the performance of the new method against the established envelope method.

Main Methods:

• Utilized a diode array rapid scan spectrometer to measure polychromatic light reflectance (300-420 nm) from DLC films.
• Implemented a two-step regression procedure to extract refractive index, bandgap, absorption edge slope, and film thickness.
• Employed simulated data to assess accuracy and robustness, particularly for strongly absorbing and noisy spectra.

Main Results:

• The two-step regression procedure reliably determined DLC film parameters, independent of initial estimation settings.
• The new method demonstrated superior accuracy compared to the envelope method for strongly absorbing films.
• The regression procedure proved effective in handling highly noisy reflectance spectra.

Conclusions:

• The developed two-step regression method offers a robust and accurate approach for optical characterization of DLC films.
• This technique provides a valuable alternative to existing methods, especially for challenging spectral data.
• The findings contribute to improved understanding and application of DLC films in various technological fields.