Simultaneous Evaluation of Heat Capacity and In-plane Thermal Conductivity of Nanocrystalline Diamond Thin Films

TL;DR

This study demonstrates a method to simultaneously measure heat capacity and in-plane thermal conductivity of nanocrystalline diamond thin films, revealing their temperature-dependent behaviors crucial for electronic device thermal management.

Contribution

The paper introduces a combined measurement approach using TDTR to evaluate both properties simultaneously, addressing previous challenges in characterizing CVD diamond films.

Findings

Thermal conductivity remains around 103 W/m·K between 302-327 K.

Heat capacity shows strong temperature dependence matching natural diamond.

Method enables better understanding of diamond's thermal properties for device applications.

Abstract

As wide bandgap electronic devices have continued to advance in both size reduction and power handling capabilities, heat dissipation has become a significant concern. To mitigate this, chemical vapor deposited (CVD) diamond has been demonstrated as an effective solution for thermal management of these devices by directly growing onto the transistor substrate. A key aspect of power and radio frequency (RF) electronic devices involves transient switching behavior, which highlights the importance of understanding the temperature dependence of the heat capacity and thermal conductivity when modeling and predicting device electrothermal response. Due to the complicated microstructure near the interface between CVD diamond and electronics, it is difficult to measure both properties simultaneously. In this work, we use time domain thermoreflectance (TDTR) to simultaneously measure the in plane thermal conductivity and heat capacity of a 1 um thick CVD diamond film, and also use the pump as an effective heater to perform temperature dependent measurements. The results show that the in plane thermal conductivity varied slightly with an average of 103 W per meter per K over a temperature range of 302 to 327 K, while the specific heat capacity has a strong temperature dependence over the same range and matches with heat capacity data of natural diamond in literature.