Picosecond Transient Thermoreflectance for Thermal Conductivity Characterization

TL;DR

This paper introduces a picosecond transient thermoreflectance (TTR) technique for measuring thermal conductivity and interface conductance in thin films and bulk materials, offering a simpler and cost-effective alternative to existing methods.

Contribution

The paper presents a novel TTR method using picosecond lasers that can measure thermal properties in thin films and bulk materials with high resolution and lower complexity.

Findings

Validated TTR measurements against reported values for various substrates.

Measured thermal conductivity of MoS2 thin films as 3.4 W/mK.

Demonstrated TTR's capability to assess in-plane and cross-plane thermal transport.

Abstract

We have developed a transient thermoreflectance technique using picosecond pulsed and cw laser to study thermal conductivity and interface conductance in both thin-films and bulk materials. A real time-resolved system observes a thermal transport along the cross-plane direction of the sample during a single pulse excitation. The suggested TTR technique can measure thermal conductivity in up to a few hundred nm of thin films with a reasonable uncertainty by carefully selecting metal transducer thickness. In this paper, we examine thermal conductivity in several substrates including Si, GaAs, Sapphire, and Glass after depositing Au thin film as metal transducer and compare with reported values to validate our technique. For further study on our method, MoS2 thin-films with different thicknesses are prepared via exfoliating, and their thermal conductivity are measured as average value of 3.4 W/mK. Compared to TDTR technique, TTR is a simpler and inexpensive method to study thermophysical properties and can also measure in-plane thermal property using a grating imaging technique. TTR can be one of the available options for observing thermal transport phenomena in both horizontal and vertical directions with a simple and inexpensive preparation.