Effects of phase changes on reflection and their wavelength dependence in optical profilometry

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Accurate measurement of optical properties is crucial for thin film applications.
• Phase changes in reflected light provide key insights into material characteristics.

Purpose of the Study:

• To present a novel method and instrumentation for measuring phase changes in reflected light.
• To investigate the optical properties of evaporated gold (Au), aluminum (Al), silver (Ag), and chromium (Cr) films.

Main Methods:

• Developed and described a new instrumentation for phase change measurement.
• Measured phase changes of Au, Al, Ag, and Cr films across five wavelengths (442–633 nm).
• Used the glass-air interface as a zero-reference point.

Main Results:

• Gold (Au) film results closely matched calculated values using handbook optical constants or ellipsometry.
• Aluminum (Al) and silver (Ag) films exhibited deviations of approximately 5 degrees (~4.4 nm shift at 633 nm).
• Chromium (Cr) films showed significant deviations up to 16 degrees (~9.8 nm shift at 442 nm).

Conclusions:

• The developed method accurately measures phase changes in thin films.
• Discrepancies in Al, Ag, and Cr films suggest potential variations in their optical constants or film structure.
• This technique offers a valuable tool for characterizing thin film optical properties.