School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14853, USA.
Department of Electrical Engineering, Columbia University, New York, New York 10027, USA.
Nat Nanotechnol. 2016 Jun;11(6):515-519. doi: 10.1038/nnano.2016.20. Epub 2016 Mar 7.
Thermal radiation between parallel objects separated by deep subwavelength distances and subject to large thermal gradients (>100 K) can reach very high magnitudes, while being concentrated on a narrow frequency distribution. These unique characteristics could enable breakthrough technologies for thermal transport control and electricity generation (for example, by radiating heat exactly at the bandgap frequency of a photovoltaic cell). However, thermal transport in this regime has never been achieved experimentally due to the difficulty of maintaining large thermal gradients over nanometre-scale distances while avoiding other heat transfer mechanisms, namely conduction. Here, we show near-field radiative heat transfer between parallel SiC nanobeams in the deep subwavelength regime. The distance between the beams is controlled by a high-precision micro-electromechanical system (MEMS). We exploit the mechanical stability of nanobeams under high tensile stress to minimize thermal buckling effects, therefore keeping control of the nanometre-scale separation even at large thermal gradients. We achieve an enhancement of heat transfer of almost two orders of magnitude with respect to the far-field limit (corresponding to a 42 nm separation) and show that we can maintain a temperature gradient of 260 K between the cold and hot surfaces at ∼100 nm distance.
在深亚波长距离和大温度梯度 (>100 K) 下分离的平行物体之间的热辐射可以达到非常高的水平，同时集中在一个狭窄的频率分布上。这些独特的特性可以为热输运控制和发电技术带来突破（例如，通过在光伏电池的带隙频率处辐射热量）。然而，由于在避免其他传热机制（即传导）的同时，很难在纳米尺度距离上保持大的温度梯度，因此，这种情况下的热输运在实验上从未实现过。在这里，我们展示了在深亚波长范围内平行 SiC 纳米梁之间的近场辐射热传递。梁之间的距离由高精度微机电系统 (MEMS) 控制。我们利用纳米梁在高拉伸应力下的机械稳定性来最小化热屈曲效应，从而即使在大温度梯度下也能保持纳米尺度的分离。与远场极限（对应于 42nm 的分离）相比，我们实现了近场辐射热传递的几乎两个数量级的增强，并表明我们可以在约 100nm 的距离内保持冷、热表面之间 260K 的温度梯度。
