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Hewlett-Packard and UCLA Collaboration Receives
Key Molecular Electronics Patent
Hewlett-Packard Company and UCLA have received a U.S. patent for technology that could make it possible to build very
complex logic chips -- simply and inexpensively -- at the molecular scale.
The collaboration is pursuing molecular electronics as an entirely new technology that could augment silicon-based
integrated circuits within the decade and eventually replace them. Most experts believe that silicon technology will
reach its physical and economic limits by about 2012.
The patent, issued to Philip J. Kuekes and R. Stanley Williams of HP Labs and James R. Heath of UCLA, builds on
previous patents and scientific work by the company and university, working under a grant from the U.S. Defense
Advanced Research Projects Agency, with matching funds from HP.
Today's chip manufacturing process involves multiple, expensive precision steps to create the complex patterns of wires
that define the computer circuit. The HP and UCLA invention proposes the use of a simple grid of wires -- each wire
just a few atoms wide -- connected by electronic switches a single molecule thick.
Previously, HP demonstrated in the laboratory how some rare earth metals naturally form themselves into nanoscopic
parallel wires when they react chemically with a silicon substrate. Two sets of facing parallel wires, oriented roughly
perpendicular to each other, could then be made into a grid, like a map of Manhattan in New York City with streets
running east-west and avenues north-south.
In a related experiment, researchers from the collaboration crossed wires the size of those used in today's computer
chips and sandwiched them around a one-molecule thick layer of electrically switchable molecules called rotaxanes.
Simple logic gates were then created electronically by downloading signals to molecules trapped between the
crosswires.
"That work demonstrated for the first time that molecules could be used as electronic devices to perform computer
logic," said Heath, UCLA chemistry professor and director of the California Nanosystems Institute.
The HP and UCLA collaboration has also patented a memory chip based on molecular switches. This invention as named one
of the top five patents of 2000 by Technology Review, a journal of the Massachusetts Institute of Technology.
"All of this work demonstrates that, in the future, programming could replace today's complex, high-precision method of
fabricating computer chips," said Kuekes, a senior scientist and computer architect at HP Labs. "Once a basic grid has
been assembled, programming could be used to implement a very complex logic design by electronically setting the
appropriate configuration switches in the molecular-scale structure."
But while simple logic circuits have been formed in previous experiments, until the most recent patent, a conceptual
barrier remained to taking full advantage of the technology and creating practical, more complex chips.
"The problem is that on a single large grid all the electrical signals would interfere with each other," said Williams,
HP Fellow and director of quantum science research, HP Labs. "It would be like removing all the traffic signals from
Manhattan and demanding a minimum speed of 30 mph -- the result would be total gridlock. Signal lights, or cut wires,
regulate the flow of traffic and make it possible to carry passengers, or information, between any two points on the
grid."
The solution proposed by the patented invention is to cut the wires into smaller lengths by turning some
"intersections" into insulators.
"Essentially, you subdivide the city into smaller neighborhoods, with smaller local streets within each neighborhood
and larger streets connecting the neighborhoods," Williams said.
The insulators are created by "cutter wires," which are chemically distinct from the others. A voltage difference
between the cutter wire and the target wire creates the insulator.
Controlling these voltages and charges also has been the subject of a previous patent(3), issued to Williams and
Kuekes last year, which provided a method to connect the molecular-scale devices to current technology, whose
components are typically about 100 times larger. Generally speaking, this control involves a special demultiplexing
technique using a chemical process to connect lithographically formed wires to the nanometer-scale wires.
About HP
Hewlett-Packard Company -- a leading global provider of computing and imaging solutions and services -- is focused on
making technology and its benefits accessible to all. HP had total revenue of $45.2 billion in its 2001 fiscal year.
Information about HP and its products can be found on the World Wide Web at
http://www.hp.com.
About UCLA and the California Nanosystems Institute
UCLA is one of the world's premier universities, renown for cutting-edge research
and innovation, undergraduate and graduate education and community service. UCLA and UC Santa Barbara have joined to
build the California Nanosystems Institute, which will help to develop the
informational, biomedical and manufacturing technologies - the nanotechnologies - that will be so influential in
science and the economy in our new century.
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