Simultaneous Determination of Thermal Conductivity and Heat Capacity in Thin Films with Picosecond Transient Thermoreflectance and Picosecond Laser Flash

ABSTRACT

Combining the picosecond transient thermoreflectance (ps-TTR) and picosecond laser flash (ps-LF) techniques, we have developed a novel method to simultaneously measure the thermal effusivity and the thermal diffusivity of metal thin films and determine the thermal conductivity ($\kappa$) and the heat capacity ($c_v$) altogether. In order to validate our approach and evaluate the uncertainties, we analyzed five different metal films (Al, Cr, Ni, Pt, and Ti) with thicknesses ranging from 297 nm to 1.2 µm. Our results on thermal transport properties and heat capacity are consistent with reference values, with the uncertainties for the thermal conductivity and the heat capacity measurements below 25% and 15%, respectively. Compared with the ps-TTR technique alone, the combined approach substantially lowers the uncertainty of the thermal conductivity measurement. Uncertainty analyses on various materials show that this combined approach is capable of measuring most of the materials with a wide range of thicknesses, including those with low thermal conductivity (e.g., mica) down to thicknesses as small as 60 nm and ultrahigh thermal conductivity materials (such as cubic BAs) down to 1400 nm. Simultaneous measurement of thermal conductivity and heat capacity enables exploration of the thermal physical behavior of materials under various thermodynamic and mechanical perturbations, with potential applications in thermal management materials, solid-state phase transitions, and beyond.

KEYWORDS:

• Picosecond transient thermoreflectance
• picosecond laser flash
• thermal conductivity
• heat capacity

Acknowledgments

The authors are grateful for the support from National Science Foundation (CBET-2211660). The authors thank Dr. Xiaojia Wang (Department of Mechanical Engineering, University of Minnesota) for her invaluable inputs and suggestions to this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15567265.2023.2255243

Additional information

Funding

This work was supported by National Science Foundation (CBET-2211660).