Ellipsometry with polarisation analysis at cryogenic temperatures inside a vacuum chamber

Area of Science:

• Materials Science
• Optical Physics
• Cryogenics

Background:

• Ellipsometry is a powerful technique for characterizing thin films.
• Traditional null ellipsometry requires rotating both polarizer and analyzer.
• Measuring optical properties of cryogenic films presents unique challenges.

Purpose of the Study:

• To develop a modified null ellipsometry technique for thin film analysis at cryogenic temperatures.
• To enable in-situ measurements of cryogenic films within a vacuum chamber.
• To overcome limitations of conventional methods in cold environments.

Main Methods:

• A modified Polarizer-Compensator-Sample-Analyzer (PCSA) ellipsometry setup was employed.
• The polarizer and compensator were rotated while the analyzer remained fixed.
• The technique was tested on condensed krypton films on a highly oriented pyrolytic graphite (HOPG) substrate at 25 K.

Main Results:

• The new null ellipsometry variant successfully determined film thicknesses and optical properties.
• Refractive indices for condensed krypton and the HOPG substrate were accurately measured.
• The method proved effective for cryogenic thin film characterization.

Conclusions:

• The developed null ellipsometry variant is suitable for precise thin film analysis at cryogenic temperatures.
• This technique facilitates in-situ optical characterization of materials in cold environments.
• The method offers a reliable approach for determining optical constants and thicknesses of cryogenic films.