Thermal Rectification in CVD Diamond Membranes Driven by Gradient Grain Structure

TL;DR

This paper demonstrates a mesoscale thermal diode using gradient grain structures in CVD diamond membranes, showing significant thermal rectification without sharp temperature changes, and explores how temperature bias and thickness affect performance.

Contribution

It introduces a novel CVD diamond thermal diode based on gradient grain structure, with a spectral model explaining thermal rectification and methods to tune its performance.

Findings

Significant thermal rectification observed in CVD diamond membranes.

Gradient grain structure enables easy fabrication of mesoscale thermal diodes.

Thermal rectification can be tuned by adjusting temperature bias and membrane thickness.

Abstract

As one of the basic components of phononics, thermal diodes transmit heat current asymmetrically similar to electronic rectifiers and diodes in microelectronics. Heat can be conducted through them easily in one direction while being blocked in the other direction. In this work, we report an easily-fabricated mesoscale chemical vapor deposited (CVD) diamond thermal diode without sharp temperature change driven by the gradient grain structure of CVD diamond membranes. We build a spectral model of diamond thermal conductivity with complete phonon dispersion relation to show significant thermal rectification in CVD diamond membranes. To explain the observed thermal rectification, the temperature and thermal conductivity distribution in the CVD diamond membrane are studied. Additionally, the effects of temperature bias and diamond membrane thickness are discussed, which shed light on tuning the thermal rectification in CVD diamond membranes. The conical grain structure makes CVD diamond membranes, and potentially other CVD film structures with gradient grain structure, excellent candidates for easily-fabricated mesoscale thermal diodes without a sharp temperature change.