Rice University scientists in Houston, Texas have created the first two-terminal memory silicon chips that can be manufactured with nanoelectronic techniques and promise to extend the limits of miniaturization subject to Moore’s Law, which states the number of devices on a circuit doubles every 18 to 24 months.
Professor James Tour initially showed how electrical current could repeatedly break and reconnect 10-nanometer strips of graphite, a form of carbon, to create a robust, reliable memory bit. With Rice colleagues Jun Yao, Douglas Natelson, and Lin Zhong, Tour demonstrated how the silicon circuits did not even need the graphite to become active switching and memory devices.
Yao, who is one of Tour’s graduate students, took the idea of a circuit without graphite to the next level. He sandwiched a layer of silicon oxide, an insulator, between semiconducting sheets of polycrystalline silicon that served as the top and bottom electrodes. Applying a charge to the electrodes creates a conductive pathway by stripping oxygen atoms from the silicon oxide and forming a chain of nano-sized silicon crystals. Once formed, the chain can be repeatedly broken and reconnected by applying a pulse of varying voltage. The nanocrystal wires are as small as 5 nanometers (billionths of a meter) wide, far smaller than circuitry in even the most advanced computers and electronic devices.
Silicon-oxide memories are compatible with conventional transistor manufacturing technology, says Tour. Austin, Texas technology design company PrivaTran is already bench testing a silicon-oxide chip with 1,000 memory elements built in collaboration with the Tour lab.
Jun Yao is the primary author of a paper describing these findings that appears today in the online edition of Nano Letters. The co-authors include Tour, a professor chemistry at Rice, Zhengzong Sun, a graduate student in Tour’s lab; Natelson, a Rice professor of physics and astronomy; and Zhong, assistant professor of electrical and computer engineering.
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