Of Carbon Nanotubes and Small Groups of Atoms
In the first two installments of this blog series (Part 1)(Part 2), we’ve touched on a variety of new developments that may allow continuing miniaturization, despite predictions of doom from some pundits. We’ve talked about some interesting things like single atom transistors, 3-D ICs and extreme ultra-violet lithography. Although conventional wisdom places the limit of silicon transistors at about 11 nm, some folks at Intel have said that they have a solution for shrinking silicon down to 10 nm, and think that they may be able to go as far as 5 nm. But the science-fiction nut in me is most fascinated by new developments at IBM and Berkeley.
Terrestrial life as we know it is, of course, based on carbon. SF writers – and, indeed, some scientists – have proposed that, because carbon and silicon share many chemical properties (for example, the ability to form long-chain polymers), it might be possible to not only derive a silicon-based organic chemistry, but to actually have silicon-based life somewhere in this wondrous and infinite universe. Interesting, but as yet still science fiction.
However, what if we were to turn this around, and look at carbon and silicon from another angle? That’s essentially what’s going on at IBM, Berkeley and other research facilities.
As we all know, today’s semiconductor technology is based on silicon. But what if we were to substitute carbon for silicon? Would it be possible to create carbon-based semiconductors? Carbon atoms are far smaller than their silicon counterparts, so this might enable heretofore unimaginable miniaturization.
IBM’s people have successfully fabricated and evaluated a structure comprising an array of 10,000 carbon nanotube transistors on a single substrate. In essence, a carbon nanotube is a single-atom thick sheet of carbon, rolled into a tube. Normally, these appear as a mix of metallic and semiconducting types but, to create a computing device, the metallic types must be removed. And, as if that wasn’t tough enough, the placement and alignment of the tubes on a substrate must be precisely controlled. IBM has been able to accomplish this utilizing ion-exchange chemistry. Researchers at Berkeley have been able accomplish a similar feat, producing arrays both flexible and stretchable, which show great promise for developments such as foldable electronic pads, coatings that can monitor surfaces for cracks and other potential failures, “smart” clothing and even artificial electronic skin.
It is theorized that carbon nanotube transistor arrays, which can be produced with existing manufacturing processes, have the potential to yield CPU structures that are not only far smaller than their silicon counterparts, but are five to ten times faster than today’s silicon chips.
It’s not clear to me whether a single nanotube can only carry a single transistor, or whether it might be possible to produce many transistors at different locations on the surface of a single nanotube. While the latter may not be “do-able” today, who can say what will be possible tomorrow?
IBM scientists have also been able to determine that only twelve atoms are required to magnetically store a single bit of information. This is accomplished by precisely aligning their magnetic properties such that they do not interfere with other groups of atoms located nearby. It is projected that this technology could increase magnetic storage density on a hard disk drive by a factor of 100.
I suppose (though this is pure speculation) that it may also be possible to create ultra-dense storage through the use of carbon nanotubes. And, since nanotubes are inherently 3-D structures, they may lend themselves to the fabrication of 3-D chips as well.
Whatever happens, two things are clear to me. First, we are nowhere near the end of miniaturization and, second, the ability to produce computing devices with human, or even superhuman, computing ability may be fairly close. Can the development of truly intelligent machines with the ability to both replicate and evolve be that far away? I certainly hope I’m still around to see this.
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