Optical layer development for thin films thermal conductivity measurement by pulsed photothermal radiometry

Area of Science:

• Materials Science
• Thermal Physics
• Nanotechnology

Background:

• Optical measurement techniques like pulsed photothermal radiometry struggle with transparent thin films.
• Accurate thermal property measurement is crucial for applications involving thin films.

Purpose of the Study:

• To develop and validate methods for measuring thermal conductivity and volumetric specific heat of optically transparent thin films.
• To investigate the impact of surface modifications and model corrections on measurement accuracy.
• To evaluate high-temperature performance of different optical layers for thermal property measurements.

Main Methods:

• Two primary approaches were employed: (i) adding an opaque optical layer and (ii) applying a mathematical model correction for film semitransparency.
• Various single-layer and multilayer optical layers were tested, with material selection based on optical properties (emissivity, absorption).
• Thermal properties of six different thin films were measured across a range of temperatures (room temperature to 500°C) using different surface configurations.

Main Results:

• The addition of opaque optical layers and model corrections enabled accurate thermal property measurements of transparent thin films.
• Observed effects of surface layers included apparent effusivity changes and time delays in thermal response.
• High-temperature testing revealed the suitability of different optical layers for measurements up to 500°C.

Conclusions:

• The presented methods effectively overcome the challenges of measuring thermal properties in optically transparent thin films.
• Surface modification and advanced modeling are crucial for reliable optical-based thermal characterization.
• The study provides valuable data for selecting appropriate measurement strategies and materials for high-temperature applications.