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At the Nanoscale, Heat Travels Much Faster Than Expected


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In a great many fields, heat transfer is of significant importance, and computer chips are no exception as circuitry reaches ever smaller sizes. On the macroscale we live on, the rules for how heat flows are well understood, but at the nanoscale the game can change and for decades a debate has continued over how to describe it. At last we appear to have an answer, thanks to researchers at the University of Michigan.

Radiative heat is the light that objects emit from the movement of particles, and over a century ago Max Planck wrote the equations that explained the process. However, as the gap between two objects shrinks, the equations start to fall apart. A new theory was developed in the middle of last century by Sergei Rytov, but some experiments reported significant differences from it. Now the Michigan researchers with a very advanced lab have confirmed Rytov's theory experimentally. The experiment involved placing a heated surface of silica, silicon nitride, or gold beneath a scanning thermal microscopy probe of the same material, and moving the probe closer to the surface. The researchers discovered that at very small distances between the surfaces and the probes, the heat flow would jump to 10,000 times that we experience on the macroscale. The reason is because the surface and evanescent waves of the two objects start to overlap at these distances.

The significance of this research is with how it will impact nanotechnologies that require controlling heat flow. It was for this reason that the researchers worked with silica, silicon nitride, and gold as all three materials are used in nanotechnologies.

Source: University of Michigan

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