Brainlike atomic switches will replace semiconductors in the future
More than 12 years after their birth in Japan, atomic switches — which many experts believe could replace semiconductors in computer chips — are now nearly ready for prime time. These energy-efficient mechanisms hold the potential to revolutionize information technology.
To be precise, the switches are expected to lead to the development of a neuromorphic chip — a chip with properties similar to neurons in the brain. Such devices may be capable of making decisions much like humans do.
NEC has started manufacturing samples of a small, power-saving and highly durable chip incorporating atomic switches. The Japanese electronics maker announced in October that it had started producing samples of the chip, which features atomic switch technology dubbed NanoBridge. Monthly production at its 300mm wafer line in Japan is expected to total up to 5,000 units.
In addition to sample shipments, NEC plans to conduct testing in outer space to verify that the new chip is less susceptible to radiation than conventional models. Thanks to their metal wiring, atomic switches rarely malfunction due to radiation and electromagnetic noise.
The new chip will be incorporated into a craft dubbed the Innovative Satellite Technology Demonstration 1, to be launched by the Japan Aerospace Exploration Agency aboard a small Epsilon rocket sometime during the fiscal year starting next April.
Down to basics
To grasp the magnitude of this technological shift, we have to wade into some rather complex basics.
Conventional semiconductor chips use transistors as switches to turn electric signals on and off. These work by controlling the movement of electrons.
Atomic switches, on the other hand, work by controlling the movement of atoms. Electrical signals are switched on and off through nano-size metallic clusters, rather than through electrical charges.
Atomic switches use no semiconductor materials, such as silicon. Instead, they use electrodes made of metals such as copper, along with solid electrolytes. Despite the differences, the manufacturing process for silicon chips is similar to that for atomic switches.
Chipmakers supply something called field-programmable gate array chips, which can be configured by customers after manufacturing, or “in the field.” Like previous FPGAs, NEC’s new chip can be customized by users to meet their requirements. But the new chip is only a third the size of its predecessors, as the switches are smaller and the technology eliminates the need for static random-access memory, or SRAM — non-volatile memory that does not need constant power.
The new FPGA chip is also about 10 times more energy-efficient than previous models, as it has a shorter wiring path and does not need standby power consumption.
Born in Japan
Atomic switch technology was created in Japan. Among the key figures were Masakazu Aono, Tsuyoshi Hasegawa and Kazuya Terabe, who formed a team at the National Institute for Materials Science.
Aono currently serves as executive adviser at the International Center for Materials Nanoarchitectonics. Hasegawa is a professor at Waseda University, while Terabe is a group leader at NIMS.
The technology they developed works like this: An atomic switch consists of a solid electrolyte electrode and a metallic electrode. There is a gap of about 1 nanometer between the two electrodes.
When a negative bias voltage is applied to the metallic electrode, metallic atoms are deposited on the surface of the solid electrolyte electrode, resulting in the formation of an icicle-like metallic cluster between the two electrodes, which turns on the switch.
The metallic cluster sticking out from the solid electrolyte electrode is the size of several atoms. When it reaches the opposite metallic electrode, the switch is turned on. The atomic switch operates by controlling the movement of several atoms.
When a positive bias voltage is applied to the metallic electrode, the deposited metallic atoms dissolve into the solid electrolyte electrode, resulting in the annihilation of the metallic cluster between the two electrodes to turn off the switch.
Atomic switch chips have the potential to replace all semiconductors, including memory chips.
Even when power is turned off, atomic switch devices do not lose data because they are non-volatile. This is why the technology is expected to make it into non-volatile memory, like flash, in the future.
Terabe, one of the developers, is paying particularly close attention to another unique property of atomic switches: their similarities to brains.
The metallic cluster that extends from the solid electrolyte electrode toward the metallic electrode is similar to a brain synapse extending, connecting neurons and thereby forming a neural circuit, strengthening the organism’s memory.
A human has both long-term, or established, and short-term, or temporary, memories. Similarly, an atomic switch device can express differences in short-term and long-term memories.
“There is a possibility that it will be used as a neuromorphic chip that has similar functions to a brain’s neural network, or as a ‘decision-making device’ that can make decisions like a human,” Terabe said.
He and his colleagues discovered the operating principle of the atomic switch around 2000. In early 2005, they announced the successful development of the switch, paving the way for production of a high-performance chip using many such switches.
Nearly two decades later, the commercialization of the groundbreaking technology is now in sight.
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