Near-Field Thermal Radiation Effectively Controlled Using Multilayered Nanostructure

A research team at KAIST was successful in measuring and regulating the near-field thermal radiation between metallo-dielectric (MD) multilayer structures.

Their thermal radiation control technology can be used in next-generation semiconductor packaging, thermal management systems, and thermophotovoltaic cells. It also can probably be applied to a sustainable energy source for IoT sensors.

In the nanoscale gaps, thermal radiation between objects increases significantly with closer distances. The amount of heat transfer in this scale was discovered to be from 1,000 to 10,000 times greater than the blackbody radiation heat transfer, which was at one time considered the theoretical maximum for the rate of thermal radiation. This occurrence is called near-field thermal radiation. With the latest developments in nanotechnology, research into near-field thermal radiation between different materials has been enthusiastically carried out.

Surface polariton coupling produced from nanostructures has been of specific interest as it improves the amount of near-field thermal radiation between two objects, and enables the spectral control of near-field thermal radiation. This advantage has enthused much of the latest theoretical research on the application of near-field thermal radiation using nanostructures, such as multilayer nanostructures, thin films, and nanowires. However, thus far, most of the studies have concentrated on measuring near-field thermal radiation between isotropic materials.

A joint team led by Professor Bong Jae Lee and Professor Seung Seob Lee from the Department of Mechanical Engineering has been successful in measuring near-field thermal radiation according to the vacuum distance between MD multilayer nanostructures by using a custom MEMS (Micro-Electro-Mechanical Systems)-device-integrated platform having three-axis nanopositioner.

MD multilayer nanostructures denote structures in which metal and dielectric layers with consistent thickness alternate. The MD single-layer pair is called a unit cell, and the ratio of the thickness occupied by the metal layer in the unit cell is termed as the fill factor.

By measuring the near-field thermal radiation with a variable number of unit cells and the fill factor of the multilayer nanostructures, the team showed that the surface plasmon polariton coupling improves near-field thermal radiation considerably, and enables spectral control over the heat transfer.

The isotropic materials that have so far been studied experimentally had limited spectral control over the near-field thermal radiation. Our near-field thermal radiation control technology using multilayer nanostructures is expected to become the first step toward developing various near-field thermal radiation applications.

Bong Jae Lee, Professor, Department of Mechanical Engineering, KAIST.

This study, led by PhD Mikyung Lim and PhD candidate Jaeman Song, was reported in Nature Communications on October 16^th.