Simultaneous Measurement of Thermal Conductivity, Heat Capacity, and Interfacial Thermal Conductance by Leveraging Negative Delay-Time Data in Time-Domain Thermoreflectance

TL;DR

This paper introduces a novel TDTR method that leverages negative delay-time data to simultaneously measure thermal conductivity, heat capacity, and interfacial thermal conductance with improved efficiency and accuracy.

Contribution

The study presents a single-frequency TDTR approach utilizing negative delay-time data, eliminating the need for multiple frequencies in thermal property measurements.

Findings

Accurately measured thermal properties of various bulk samples.

Successfully determined interface thermal conductance for multiple thin films.

Demonstrated method's effectiveness with a single modulation frequency.

Abstract

Time-domain thermoreflectance (TDTR) is a widely used technique for characterizing the thermal properties of bulk and thin-film materials. Traditional TDTR analyses typically focus on positive delay time data for fitting, often requiring multiple-frequency measurements to simultaneously determine thermal conductivity and heat capacity. However, this multiple-frequency approach is cumbersome and may introduce inaccuracies due to inconsistencies across different frequency measurements. In this study, we propose a novel solution to these challenges by harnessing the often-overlooked negative delay time data in TDTR. By integrating these data points, we offer a streamlined, single-frequency method that simultaneously measures thermal conductivity, heat capacity, and interface thermal conductance for both bulk and thin-film materials, enhancing measurement efficiency and accuracy. We demonstrate the effectiveness of this method by measuring several bulk samples including sapphire, silicon, diamond, and Si0.992Ge0.008, and several thin-film samples including a 1.76-{\mu}m-thick gallium nitride (GaN) film epitaxially grown on a silicon substrate, a 320-nm-thick gallium oxide ({\epsilon}-Ga2O3) film epitaxially grown on a silicon carbide substrate, and a 330-nm-thick tantalum nitride (TaN) film deposited on a sapphire substrate, all coated with an aluminum (Al) transducer layer on the surface. Our results show that the new method accurately determines the thermal conductivity and heat capacity of these samples as well as the Al/sample interface thermal conductance using a single modulation frequency, except for the Si0.992Ge0.008 sample. This study sheds light on the untapped potential of TDTR, offering a new, efficient, and accurate avenue for thermal analysis in material science.