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A 5 nm silicon nanowire can be repeatedly broken and reconnected by applying a pulse of varying voltage through the silicon oxide, creating a two-terminal resistive switch. A chip with 1000 of these silicon-oxide/silicon nanowire memory elements has been assembled as a proof-of-concept.(Credit: Jun Yao/Rice.)

It’s not often that “plain vanilla” silicon oxide makes the front page of a paper like the New York Times, but it happened when Rice University scientists announced that they have created the first two-terminal memory chips based on silicon oxide in a way that they say should be easily adaptable to nanoelectronic manufacturing techniques, and promises to extend the limits of miniaturization subject to Moore’s Law.

Their technique creates nanocrystal wires that are as small as 5 nanometers wide, far smaller than circuitry in even the most advanced computers and electronic devices. The Rice group believes its nanocrystal conductors could lead to massive, robust 3-D storage.

“The beauty of it is its simplicity,” says James Tour, Rice’s T.T. and W.F. Chao chair in chemistry as well as a professor of mechanical engineering and materials science and of computer science. That, he said, will be key to the technology’s scalability. Silicon-oxide switches or memory locations require only two terminals, not three (as in flash memory), because the physical process doesn’t require the device to hold a charge.

According to the Rice press release:

“[Graduate student] Jun Yao 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 created 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.”

Layers of silicon-oxide memory can be stacked in three-dimensional arrays. “I’ve been told by industry that if you’re not in the 3-D memory business in four years, you’re not going to be in the memory business. This is perfectly suited for that,” Tour says.

Silicon-oxide memories are compatible with conventional transistor manufacturing technology, says Tour, who recently attended a workshop by the National Science Foundation and IBM on breaking the barriers to Moore’s Law, which states the number of devices on a circuit doubles every 18 to 24 months.

Austin tech design company PrivaTran is already bench testing a silicon-oxide chip with 1,000 memory elements built in collaboration with the Tour lab.

The findings were published in Nano Letters.

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Live Science reported that researchers have built a new super-small “nanodragster” that could speed up efforts to craft molecular machines.

“We made a new version of a nanocar that looks like a dragster,” said James Tour, a chemist at Rice University who was involved in the research. “It has smaller front wheels on a shorter axle and bigger back wheels on a longer axle.”

The vehicle is about 50,000 times thinner than a human hair and is pushed along by heat or an electric field.

Spherical molecules called buckyballs made of 60 carbon atoms each serve as the big rear wheels. Due to chemical attractions, these wheels nicely grip the “dragstrip,” which is made of a superfine layer of gold rather than pavement. For the front wheels, the scientists opted for a less sticky compound, p-carbonane.

Tour’s group built nanocars before with buckyballs as all four wheels, but these autos hug the road too tightly and require temperatures around 400 F to get rolling. Nanocars with all p-carbonane wheels, on the other hand, slip and slide as if on ice, said Tours, making them difficult to image and study.

By incorporating both wheel types, the nanodragster can cruise at lower temperatures with greater agility and range of motion.

To make the new nanodragster, Tour’s team started with a previously built, off-the-shelf short axle and front wheel unit in their lab, which is sort of a nano-Monster Garage. They then chemically hooked this up to a pair of aligned hydrocarbon molecules called phenylene-ethynylene-the vehicle’s chassis. The rear axle came next and finally the buckyball wheels went on.

Once the new nanocar gets rolling, it can reach speeds of up to nine nanomiles, or 0.014 millimeters (.0005 inches), per hour, which is relatively fast for their size, said Tour.

The tiny hot rods can also do tricks. “Because the front wheels don’t stick to the surface as strongly, they’re more prone to lift up, so [the nanodragster] does seem to pop a wheelie at times,” Tour told Top Ten Reviews.

By learning how to drive nanovehicles, Tour hopes to pave the way for small but technologically useful structures, such as electronics, that could be built atom-by-atom.

The research appeared in a recent issue of the journal Organic Letters.

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