# 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.

## Key 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.

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Source: https://tomesphere.com/paper/1907.09638