International audienc

No abstract

In this letter, we have designed a near-field thermal rectifier using a film and a bulk of doped silicon, with different doping levels, separated by a vacuum gap. We examine the origin of nonlinearities in thermal rectification associated with near-field heat transfer, and investigate closely the effects of varying the vacuum gap and the film thickness on rectification. For a 10 nm thick film, rectification greater than 0.5 is achieved for vacuum gaps varying from 1 nm to 50 nm with the hot and cold temperatures of the terminals of the rectifier being 400 K and 300 K, respectively. The results obtained from this study may benefit future research in thermal management and energy harvesting.

Using Rytov's fluctuational electrodynamics framework, Polder and Van Hove predicted that radiative heat transfer between planar surfaces separated by a vacuum gap smaller than the thermal wavelength exceeds the blackbody limit due to tunnelling of evanescent modes. This finding has led to the conceptualization of systems capitalizing on evanescent modes such as thermophotovoltaic converters and thermal rectifiers. Their development is, however, limited by the lack of devices enabling radiative transfer between macroscale planar surfaces separated by a nanosize vacuum gap. Here we measure radiative heat transfer for large temperature differences (∼120 K) using a custom-fabricated device in which the gap separating two 5 × 5 mm2 intrinsic silicon planar surfaces is modulated from 3,500 to 150 nm. A substantial enhancement over the blackbody limit by a factor of 8.4 is reported for a 150-nm-thick gap. Our device paves the way for the establishment of novel evanescent wave-based systems.