Super-Planckian Radiative Heat Transfer between Metallic Surfaces Due to Near-Field and Thin-Film Effects

TL;DR

This study experimentally demonstrates that near-field and thin-film effects can significantly enhance radiative heat transfer between metallic surfaces beyond the blackbody limit, with potential applications in thermal management and energy conversion.

Contribution

The paper provides the first experimental validation of super-Planckian radiative heat transfer between metallic surfaces due to near-field and thin-film effects, supported by theoretical calculations.

Findings

Heat flux exceeds blackbody limit by 6.4 times at 215 nm gap.

Near-field enhancement predicted to reach 122 times over blackbody.

Experimental and theoretical results show significant super-Planckian heat transfer.

Abstract

In this Letter we experimentally demonstrate that the radiative heat transfer between metallic planar surfaces exceeds the blackbody limit by employing the near-field and thin-film effects. Nanosized polystyrene particles were used to create a nanometer gap between aluminum thin-films of different thicknesses coated on 5x5 mm2 diced silicon chips while the gap spacing is fitted from the near-field measurement with bare Si chips. The experimental results are validated by theoretical calculation based on fluctuational electrodynamics. The near-field radiative heat flux between 13-nm Al thin-film samples at 215 nm gap distance is measured to be 6.4 times over the blackbody limit and 420 times compared to the far-field radiative heat transfer between metallic surfaces with a temperature difference of 65 K. In addition, the theoretical prediction suggests a near-field enhancement of 122 times relative to the blackbody limit and 8000 times over far-field one at 50-nm vacuum gap between 20-nm Al thin-film samples, under the same temperature difference of 65 K. This work will facilitate the understanding and application of near-field radiation to thermal power conversion, noncontact cooling, heat flow management, and optical storage where metallic materials are involved.