A Thermal Diode Based on Nanoscale Thermal Radiation

In this work we demonstrate thermal rectification at the nanoscale between doped Si and VO₂ surfaces. Specifically, we show that the metal-insulator transition of VO₂ makes it possible to achieve large differences in the heat flow between Si and VO₂ when the direction of the temperature gradient is reversed. We further show that this rectification increases at nanoscale separations, with a maximum rectification coefficient exceeding 50% at ∼140 nm gaps and a temperature difference of 70 K. Our modeling indicates that this high rectification coefficient arises due to broadband enhancement of heat transfer between metallic VO₂ and doped Si surfaces, as compared to narrower-band exchange that occurs when VO₂ is in its insulating state. This work demonstrates the feasibility of accomplishing near-field-based rectification of heat, which is a key component for creating nanoscale radiation-based information processing devices and thermal management approaches.