Berkeley Lab scientists discover material to improve device speed

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A three-year research study at the Lawrence Berkeley National Lab, or LBNL, has resulted in the discovery of a rare material that makes electronic devices work faster due to its ability to conduct heat more efficiently.

According to study author and campus materials science and engineering professor Junqiao Wu, the discovery came to fruition when his graduate student Penghong Ci was trying to improve ways to conduct heat more efficiently in chips. of silicon.

“We found a material that can conduct heat much better than what we currently use in our computer chips,” Wu said. by burning it.”

According to the research paper, each computer chip is made up of tens of billions of transistors — the basic units of silicon chips — where electrical currents flow and generate heat. However, when silicon is reduced to small sizes, it becomes ineffective in conducting heat transfer.

Wu said silicon is made up of three different types of isotopes: silicon-28, silicon-29, and silicon-30. When silicon is purified into a single piece of isotopically pure silicon-28, it conducts heat more efficiently because both silicon-29 and silicon-30 contain slightly heavier atoms that slow heat conduction.

Wu added that the obstruction of heat by silicon-29 and silicon-30 is akin to the obstruction of a wave of water by a physical object when you throw a stone into a swimming pool.

Although isotopically pure silicon-28 is a rare material that is not sold commercially, it was provided to Wu’s research team by LBNL scientist Joel Ager. Wu said the lab had obtained silicon-28 in the 1990s for study from former universities in the Soviet Union, and Ager had access to some of the remaining material.

“They probably haven’t used this material for 20 years until a few years ago when we had the idea of ​​measuring the thermal conductivity of nanowires,” Wu said.

The research paper notes that heat transport in silicon nanowires is difficult due to rough surfaces that “scatter” atomic vibration waves that transport heat.

As a result, Wu said his team decided to make a nanowire from isotopically pure silicon-28 and found that the thermal conduction was improved by 150% compared to that of natural silicon nanowires of the same size and roughness. surface.

“We believe that with our current discovery, we could potentially find hardware that can make the computer faster and run at a much higher frequency,” Wu said.

Besides improving thermal conductivity, Wu said that isotopically pure silicon-28 can also perform all “other electronic functionality”.

In the next steps, Wu and his team plan to fabricate a silicon-28 transistor and compare its functionality to a natural silicon transistor to see if this material change improves the transistors.

“If this experiment is approved, then we will have a big breakthrough here and we can make computer chips or integrated circuits that can operate at higher power and higher speed without crashing,” Wu said.

Dhoha Bareche is a research and ideas journalist. Contact her at [email protected].

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