Thermal rectification enabled by near-field Radiative heat transfer between intrinsic silicon and a dissimilar material

Thermal rectification has recently attracted great attention because it could allow heat to flow in a preferred direction and may have promising applications in thermal management and energy systems. In addition to phonon engineering, photon transport at the near-field regime has been recently proposed to realize thermal rectification between planar structures. In the present study, the thermal rectification effect enabled by near-field thermal radiation between intrinsic silicon and other materials was investigated at various temperatures and vacuum gap distances. Strong thermal rectification between intrinsic Si and doped Si (rectification R = 2.7) and between intrinsic Si and SiO₂ (R = 9.9) can be achieved with a 5 nm vacuum gap at temperatures of 1000 and 300 K. Rectification larger than one can be obtained in sub-10 nm vacuum gaps for the former configuration and sub-20 nm gaps for the latter configuration. A thermal rectifier made of gold and intrinsic Si is shown to have a rectification factor around 0.85 with temperatures of 600 and 300 K at a wide range of vacuum gaps from 100 to 500 nm. The physical mechanisms of the rectification effect in the three configurations are elucidated, and each of the proposed thermal rectifiers may have its own advantage for applications dealing with different temperatures and vacuum distances.