Potential of porous silicon in the cooling circuits
A team led by Tszaeho Li, the University of California at Irvine demonstrated the potential of porous silicon in the cooling circuits. The scientists found out that the microscopic holes made in the right places are the “conductors” for heat, which divert excess energy into the points intended for this purpose.
Each sign is a quiet rustle of the fan accompanying the work of a stationary computer or laptop. In powerful computing and data centers, cooling becomes a serious problem. Sometimes they are specially built on the seashore so that there is no shortage of cold water for the radiators.
No fewer difficulties create excessive heat in small devices. After all, in a smartphone or smart clock, the fan does not belong. At the same time, engineers tend to pack as many transistors as possible on a square millimeter to increase the speed and memory capacity. Could someone have thought about 20 years ago that a device with several gigabytes of RAM will fit in a pocket? However, the denser the heated parts are, the more difficult it is to cool them.
Lee’s team came to the matter scientifically. In early 2017, scientists published in the journal Nature Communications article, which investigated the propagation of phonons in silicon wafers.
The phonon is a quasiparticle that describes the vibrations of the crystal lattice. In short, we are talking about the fact that physicists often find it convenient to represent the process under study as the motion of particles with certain characteristics (charge, and so on). Such particles are a model that simplifies calculations, that is, in reality, they do not exist (for example, one can not observe the flow of these particles in a vacuum). Therefore, they are called quasiparticles.
Let’s return to the crystals. Their thermal conductivity is determined by the vibrations of the atoms so that the photons have the most direct relation to it. Relying on their results on the study of these quasiparticles, in a new work the scientists investigated the thermal properties of silicon wafers in which vertical pores of nanometer diameter were created.
“We found that heat prefers to spread through porous silicon vertically, but not across the pores, which means that the material can efficiently transfer heat from local hot spots to cooling systems,” Lee explains in a press release .
Thus, it is possible to create channels in the right places for heat removal, which is much easier than cooling the entire system as a whole.
The thing is that the pores cause backscattering of photons, which prevents their propagation across the channel. At the same time, photons with a long wavelength (we recall that quantum particles exhibit wave properties) effectively transport heat along a “paved path”.
Laboratory studies have shown that such plates are cooled four times more efficiently than those equipped with standard cooling devices based on chalcogenides.
The new technology is important not only because it will allow to further reduce the size of electronic devices. Heating is one of the main factors of electronics wear. Effective cooling will increase the durability of gadgets, and hence, reliability. This is important in a world where computers already run cars.
“On the one hand, nanotechnology has opened up a whole new world of possibilities, but on the other hand, it has created a lot of problems,” concludes Lee. “It is important that we continue to improve understanding of the fundamentals of heat transport and find ways to manage the transfer of heat at nanoscales.”