The devices, which process data in a similar way to synapses, are based on hafnium oxide and self-assembled barriers that can be raised or lowered to allow electrons to pass.
According to the team, this method of changing the electrical resistance in computer memory devices, and allowing information processing and memory to exist in the same place, could lead to the development of computer memory devices with far greater density, higher performance and lower energy consumption. The results are reported in Science Advances.
Within the next few years, artificial intelligence, internet usage, algorithms and other data-driven technologies are expected to consume over 30 per cent of global electricity.
“To a large extent, this explosion in energy demands is due to shortcomings of current computer memory technologies,” said first author Dr Markus Hellenbrand, from Cambridge’s Department of Materials Science and Metallurgy. “In conventional computing, there’s memory on one side and processing on the other, and data is shuffled back between the two, which takes both energy and time.”
One potential solution is resistive switching memory. Conventional memory devices are capable of two states, namely one or zero, but a functioning resistive switching memory device would be capable of a continuous range of states. Computer memory devices based on this principle would be capable of far greater density and speed.
“A typical USB stick based on continuous range would be able to hold between ten and 100 times more information, for example,” Hellenbrand said in a statement.
Hellenbrand and his colleagues developed a prototype device based on hafnium oxide, an insulating material already used in the semiconductor industry. The issue with using this material for resistive switching memory applications is known as the uniformity problem. At the atomic level, hafnium oxide has no structure, with the hafnium and oxygen atoms randomly mixed, making it challenging to use for memory applications.
The researchers found that by adding barium to thin films of hafnium oxide, some unusual structures started to form, perpendicular to the hafnium oxide plane, in the composite material.
These vertical barium-rich ‘bridges’ are highly structured, and allow electrons to pass through, while the surrounding hafnium oxide remains unstructured. At the point where these bridges meet the device contacts, an energy barrier was created, which electrons can cross. The researchers were able to control the height of this barrier, which changes the electrical resistance of the composite material.
“This allows multiple states to exist in the material, unlike conventional memory which has only two states,” said Hellenbrand.
Unlike other composite materials, which require expensive high-temperature manufacturing methods, these hafnium oxide composites self-assemble at low temperatures. The composite material showed high levels of performance and uniformity, making them highly promising for next-generation memory applications.
A patent on the technology has been filed by Cambridge Enterprise, the University’s commercialisation arm.
“What’s really exciting about these materials is they can work like a synapse in the brain: they can store and process information in the same place, like our brains can, making them highly promising for the rapidly growing AI and machine learning fields,” said Hellenbrand.
The researchers are now working with industry to carry out larger feasibility studies on the materials, to understand more clearly how the high-performance structures form.
The research was supported in part by the US National Science Foundation and the Engineering and Physical Sciences Research Council (EPSRC).
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