Materials opportunities and challenges for low-energy computing: Devices
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Energy Sector Analysis
Computing power demand is expected to grow exponentially as millions in developing countries go online, along with a burgeoning number of Internet-connected devices.
Materials opportunities and challenges for low-energy computing: Devices By Prachi Patel Feature Editor: Subhash L. Shinde
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omputing has progressed at a mind-bending pace in the past decades. As the world gets more digitally connected, and the amount of data processed, shared, and stored explodes, so do the energy use and environmental impact of computing. Already, computing uses 5% of the electrical power the world consumes. Much of that goes to factory-sized server farms that store digital data from billions of smartphones and tablets as people stream movies, share photos and videos, and send emails. “These things don’t come for free in terms of energy use,” said Asif Khan, a professor of electrical and computer engineering at the Georgia Institute of Technology. And the energy cost of computing is in for a steep increase. “Probably a third of the world’s population has access to highspeed Internet now,” he said. “Fast forward 10 years, and that number will more than double.” Computing power demand is expected to grow exponentially as millions in developing countries go online, along with a burgeoning number of Internet-connected devices: phones, cars, robotic vacuum cleaners, and smart TVs. A recent study projects that the information and communications technologies industry could produce up to 5.5% of the world’s carbon emissions by 2025 and 14% by 2040. “Unless we do something radical with our devices to curb energy use,” said Khan. During the past five decades, the semiconductor industry has gained performance and efficiency by shrinking silicon-based CMOS (complementary metal oxide semiconductor) devices, as governed by Moore’s Law, which predicts the number of transistors on a chip doubling every two years while the costs halve. But, said Vijay Narayanan, IBM Fellow and senior manager, PCM & AI Materials, at the IBM T.J. Watson Research Center, “the amount of data being used has gone up exponentially, and at the same time, Moore’s Law scaling has slowed down.” For more powerful computers that use less energy per bit of calculation, researchers are exploring new materials technologies that can take computing beyond CMOS. To understand why computing is energy-intensive, zoom in on one of the billions of transistors that flip digital zeroes and ones to perform the logic operations that happen behind the scenes as people map routes or upload photos. Traditional transistors are planar three-terminal devices with a silicon channel capped at either end with the source and drain, and a dielectric gate on top bridging the two. The voltage at the gate controls the flow of current between the source and drain on the order of milliamps. Each transistor requires 1 V to operate, using a million times more energy for that one-bit
calculation as it theoretically should, based on a thermodynamic calculation carried out by Rolf La
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