January 25, 2007
Chips Go Molecular
Researchers from the California Institute of Technology and the University of California, Los Angeles have built a memory chip that is roughly the size of a white blood cell, about one-2,000th of an inch on a side.
Published in the Jan. 25 issue of the journal Nature, scientists show the successful demonstration of a large-scale, "ultra-dense" memory device that stores information using reconfigurable molecular switches. This research represents an important step toward the creation of molecular computers that are much smaller and could be more powerful than today’s silicon-based computers.
To build the chip, the researchers etched 400 parallel wires, each less than a millionth of an inch wide and separated by about one-750,000th of an inch from its neighbors. On top of the wires, they deposited a layer of the molecular switches, the dumbbells standing vertically, and then a second set of 400 wires turned 90 degrees to the first set.
The paper describes the fabrication and operation of a memory device. The memory is based on a series of perpendicular, crossing nanowires, similar to a tic-tac-toe board, with 400 bottom wires and another 400 crossing top wires. Sitting at each crossing of the tic-tac-toe structure and serving as the storage element are approximately 300 bistable rotaxane molecules. These molecules may be switched between two different states, and each junction of a crossbar can be addressed individually by controlling the voltages applied to the appropriate top and bottom crossing wires, forming a bit at each nanowire crossing.
The 160-kilobit molecular memory was fabricated at a density of 100,000,000,000 (1011) bits per square centimeter This is described as a density that has been predicted for commercial memory devices around the year 2020.
Not everything about the chip works yet. When the researchers tested a small part of it, they found that only 30 percent of the bits actually worked. But it is possible to use only the working parts of the chip, and the researchers successfully wrote and read information to those parts, though even there the success was temporary. The switches routinely broke after being flipped about 10 times.
While this research could affect the computer industry dramatically, it also may have a significant impact on very different uses of information technologies as well according to the researchers. Molecular switches will lead to other new technologies beyond molecular electronic computers. such as health care, alternative energy and homeland security.
The research was funded by Defense Advanced Research Projects Agency and the National Science Foundation.
Source: New York Times
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