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Heat waves observed in semiconductor materials

An amplified frequency domain thermal reflection setup used to study the presence of germanium second sound. Use the microscope objective to focus two different lasers on the surface of the sample. A fairly large combination of optics allows you to control and change the size and shape of the spot, as well as the laser output and harmonic modulation. Cold nitrogen gas is used to better visualize the optical path of the laser. Credit: ICMAB, CSIC

Studies published in Science Advances For the first time, we report the unexpected observation of the heat wave of germanium, which is a semiconductor material. This phenomenon could significantly improve the performance of our electronic devices in the near future. This research is led by researchers at the Barcelona Institute of Materials Science (ICMAB, CSIC) in collaboration with researchers at the Autonomous University of Barcelona and the University of Caliari.


As we know, heat is generated by the vibration of atoms and is transferred by diffusion at ambient temperature. Unfortunately, it’s pretty difficult to control and leads to a simple and inefficient strategy for operation. This is why, for example, computers, mobile phones, and generally most electronic devices can accumulate large amounts of residual heat.

However, when heat is transported via waves such as light, it provides a new alternative for controlling heat, especially through the unique properties of the waves.

Heat waves have been observed only in some materials so far, such as solid helium and more recently graphite.Well, the research published in Science Advances Researchers at the Barcelona Institute of Materials Science (ICMAB, CSIC), in collaboration with researchers at the Autonomous University of Barcelona and the University of Caliari, report on the observation of heat waves in solid germanium. Semiconductor material It is commonly used in electronic devices and, like silicon, it is used at room temperature. “We weren’t expecting to encounter these wave-like effects. Second sound, About this type of material, and in these conditions, “said Sebastián Reparaz, ICMAB researcher and leader of the Nanostructure Materials (NANOPTO) group for optoelectronics and energy harvesting.

The observations occurred when the thermal response of the germanium sample was studied under the influence of a laser and a high frequency oscillating heating wave was generated on its surface. Experiments have shown that, contrary to what was previously believed, heat was not dissipated by diffusion, but propagated through heat waves to the material.

Apart from the observations themselves, in this study, researchers reveal an approach that unleashes heat wave observations, perhaps in any material system.

What is a second sound and how can it be observed on any material?

Wave heat transport, first observed in solid helium in the 1960s, known as second sound, has been a recurring subject for researchers who have repeatedly attempted to demonstrate its existence in other materials. A recent successful demonstration of this phenomenon on graphite has activated its experimental work.

“Second sound is not a diffuse regime that is often observed, but a heat regime in which heat can propagate in the form of heat waves. This type of wave-like heat transport is provided by waves, such as interference and diffraction. There are many advantages. ” ICMAB researcher Sebastián Reparaz.

“The wave-like effect is unleashed by driving the system in a rapidly changing temperature field. In other words, the rapidly changing temperature field forces heat transfer in the wave-like region.” “Interesting conclusions: These wave-like effects can be potentially observed by most materials at sufficiently large modulation frequencies of the temperature field,” explained Reparaz. That is, more interestingly, the observations are not limited to any particular material. “

Application of second sound in the near future

“The possible uses of the second sound are endless,” says Sebastián Reparaz. However, to achieve these applications, you need to have a deep understanding of how to unlock this heat transfer regime with specific materials. Being able to control heat propagation through wave properties opens up new ways to design next-generation thermal devices in a manner similar to the well-established development of light. “Specifically, a second sound thermal regime can be used to rethink how waste is treated. heat“” He added.

From a theoretical point of view, “These discoveries allow us to unify the current theoretical model. Materials that have been observed to have this kind of wavy behavior (such as graphite) are now used in manufacturing. It was thought to be very different from the semiconductor materials used in it. Development of electronic chips (such as silicon and germanium), “said UAB researcher F. Xavier Álvarez. “Currently, all these materials can be described using the same equation. This observation establishes a new theoretical framework that could significantly improve the performance of electronic devices in the not too distant future.” Alvarez adds.


Scientists Find New Solid Materials For Temperature Control


For more information:
“Observation of second sound in Ge’s rapidly changing temperature field” Science Advances (2021). Advances.sciencemag.org/lookup… .1126 / sciadv.abg4677

Quote: Heat waves observed in semiconductor materials (June 30, 2021) were obtained from https://phys.org/news/2021-06-thermal-semiconductor-materials.html on June 30, 2021. I did.

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https://phys.org/news/2021-06-thermal-semiconductor-materials.html Heat waves observed in semiconductor materials

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