What is negative capacitance and how can it reduce the huge power demand of computers?

More and more aspects of our lives are being digitized, which means that computers are becoming more and more part of the way we socialize, do business and entertain ourselves.

On the other hand, all these state-of-the-art computers require large amounts of energy. In fact, in the United States alone, IT is on track to overtake other energy-dependent sectors, such as transportation.

Meanwhile, the data centers of social media platforms like Facebook are also taking a huge energy hit, consuming more than 200 terawatt hours each year, more than the electricity demands of entire nations.

Technology is advancing at a rapid pace

In an exciting new development, a team of engineers from the University of California, Berkeley report finding a solution to reduce computer power requirements without compromising performance or size.

They did this by modifying their transistors with a new component called gate oxide, which is used to turn the transistor on and off. “We were able to show that our gate oxide technology is better than commercially available transistors,” says Sayeef Salahuddin, professor of electrical engineering and computer science at UC Berkeley.

Salahuddin and his team exploited an effect discovered more than a decade ago called negative capacitance, which helps reduce the amount of voltage needed to store electrical charge in a material.

Now, in new research, the results of which have been published in a study, engineers demonstrate how this effect can be achieved in a specially manufactured crystal made from a layered stack of hafnium oxide and zirconium oxide. , which is compatible with advanced silicon transistors.

Not just for computers

Smartphones, tablets, laptops and desktop computers contain billions of these tiny silicon transistors, each of which must be controlled by the application of a voltage. The gate oxide is a thin layer of material that converts this voltage into an electrical charge, which then turns on the transistor.

“Negative capacitance can increase gate oxide performance by reducing the amount of voltage needed to achieve a given electrical charge,” he explains. Berkeley News.

“But the effect cannot be achieved in any material. Creating negative capacitance requires careful manipulation of a material property called ferroelectricity, which occurs when a material exhibits a spontaneous electric field.”

“Previously, the effect was only achieved in ferroelectric materials called perovskites, whose crystal structure is not compatible with silicon. In the study, the team showed that negative capacitance can also be achieved by combining hafnium oxide and zirconium oxide in an engineered crystal structure called a superlattice, simultaneously leading to ferroelectricity. and antiferroelectricity.”

Through trial and error, engineers discovered that a superlattice structure made up of three atomic layers of zirconium oxide sandwiched between two single atomic layers of hafnium oxide, less than two nanometers thick , provided the best negative ability effect.

“Because most state-of-the-art silicon transistors already use a 2-nanometer oxide gate composed of hafnium oxide on silicon dioxide, and because zirconium oxide is also used in silicon technologies , these superlattice structures can be easily integrated into advanced transistor systems,” says Berkeley.

New evidence sparks optimism

Tests showed that this superlattice structure performed well as gate oxides, and transistors containing them would require about 30% less voltage than current transitions, even maintaining industry benchmarks and standards of semiconductor reliability.

“One of the problems that we often see in this type of research is that we can demonstrate various phenomena in materials, but these materials are not compatible with advanced computational materials, so we cannot benefit from real technology. “, explains Salahuddin. . “This work turns an academic subject’s negative capacitance into something that could actually be used in an advanced transistor.”

With this technical advancement, the negative capacitance effect can significantly reduce the amount of voltage required to drive transistors, and as a result computers will require significantly less power throughout their life cycle.

“Over the past 10 years, the energy used for computing has grown exponentially, already accounting for single-digit percentages of global energy production, which is only growing linearly, with no end in sight” , observes Salahuddin.

“Usually when we use our computers and mobile phones, we don’t think about how much energy we use,” adds the scientist. “But it’s a huge sum, and it’s only going to get bigger. Our goal is to reduce the power requirements of this basic component of computing, as this reduces the power requirements of the entire system. »

By Sustainability Times. Articles in English

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