From: Michael M. Butler (mmb@spies.com)
Date: Thu May 08 2003 - 22:31:55 MDT
> ON THE TUBE
>
> May 8th 2003
>> From The Economist print edition
> http://www.economist.com/science/displayStory.cfm?story_id=1763552
>
>
>
> A new type of computer memory uses carbon, rather than silicon
>
> WAITING for a computer to turn on is a nuisance. That is why
> manufacturers
> have been trying to create ³non-volatile² memories. These would be fast,
> like the random-access memory (RAM) chips that are currently used for
> often-accessed memory, but they would also continue to store information
> even without power, like hard drives, which are too slow to use except
> for
> long-term storage.
>
> Several technologies have been competing to become the standard for fast,
> non-volatile memory. The best known is magnetic RAM, which IBM and
> Motorola
> are touting. Others are based on polymers or on strange-sounding metal
> alloys called chalcogenides that change shape when an electric charge is
> applied to them. But there is now a new entrant to the field: carbon.
>
> Carbon comes in many forms. Diamonds and graphite are two of the most
> familiar ones. A less familiar variety is the nanotube, also known as a
> ³buckytube² after Richard Buckminster Fuller, whose geodesic domes have a
> framework similar to the arrangement of the atoms in a nanotube.
> Nanotubes
> consist of a cylindrical array of carbon atoms whose diameter is only
> about
> 1 nanometre (a billionth of a metre). If Nantero, a firm based in Woburn,
> Massachusetts, proves correct, such tubes will soon be an integral part
> of
> computer memories.
>
> Nantero's memory chips consist of billions of nanotubes, each a few
> hundred
> nanometres long, suspended from a silicon wafer. Another wafer sits about
> 100 nanometres below the first. Because the nanotubes that Nantero uses
> conduct electricity, a small electric charge at one point on the second
> wafer will draw several dozen nanotubes towards it. Once they are there,
> they stay there. That is because they are bound by Van der Waals
> forces‹intermolecular bonds that do not depend on external power for
> their
> maintenance. An additional application of current, however, will release
> the
> nanotubes. This means that a group of a few dozen nanotubes can act as a
> memory element, storing a single bit (either a one or a zero) of the
> binary
> code that computers use to operate. If the connection between the wafers
> is
> live at a particular point, the bit represented is a one. If not, it is a
> zero.
>
> If nanotubes were not so small, this would not be a big deal. Because
> they
> are, though, Nantero's technology can already achieve a data density
> considerably higher than existing RAMs. And because the wafers are so
> close
> together, those data can move rapidly from place to place. Nantero's new
> memory can read or write a bit in as little as half a nanosecond
> (billionth
> of a second). The best RAM chips, by contrast, need ten nanoseconds to
> perform a similar operation.
>
> At the moment, Nantero has only a working prototype. But the firm aims to
> have memories on the market within a year. It thinks it will be able to
> tool
> up for commercial production quickly, because the fabrication technique
> it
> uses, though novel, relies on standard semiconductor-making technology.
>
> The main difficulty faced by others who have tried to go down the
> buckytube
> route is getting the tubes to align with each other when they are hung
> from
> the first wafer. Until now, the approach has been to try to grow all of
> the
> tubes in the correct orientation to start with. But Nantero's founders
> came
> up with a simpler, if less elegant, solution. They use established
> lithographic techniques to get rid of tubes that are pointing in the
> wrong
> direction by zapping them with an electron beam. That leaves only those
> that
> are hanging down towards the opposite wafer.
>
> Though the recent chip is certainly impressive, the reason for getting
> excited about Nantero is not so much the present as the future. Unlike
> silicon, which is pushing against its physical limitations, carbon-
> nanotube
> technology is in its infancy. Greg Schmergel, Nantero's boss, says that
> within the next few years the firm's engineers may be able to achieve
> data
> densities of a trillion bits per square centimetre (more than 1,000 times
> that available on existing RAM) and it will be possible to read those
> memories 100 times faster than can be done at the moment. The days of
> silicon-based memory may be numbered.
>
>
>
>
>
-- I am not here to have an argument. I am here as part of a civilization. Sometimes I forget.
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