Attenuating Super-Planckian Radiative Heat Transfer in Nanoscale Structures

Radiative heat transfer between nanoscale (i.e., subwavelength) structures, with dimensions smaller than the thermal wavelength, can significantly surpass the far-field blackbody limit (Thompson, D.; et al. Nature 2018). This enhanced thermal coupling, called super-Planckian radiative heat transfer, limits the performance of high-resolution calorimeters [often made of silicon nitride (SiN)] used in nanoscale thermal sensing. Here, via computational and experimental work, we show that super-Planckian coupling can be significantly attenuated by employing polymers. Our calculations show that Parylene-C (a polymer) exhibits a lower density of guided-modes and reduced absorption across the thermal spectrum, suppressing this coupling by up to 10-fold compared to SiN. Experiments performed with custom-fabricated Parylene-C and SiN devices confirm that the radiative coupling is indeed attenuated in Parylene-C. Our findings highlight how the super-Planckian coupling can be attenuated for improved performance in high-resolution calorimetry.