Recently Xidex Corp. and SEMATECH, a non-profit semiconductor industry consortium, both based in Austin, Texas, announced a capability that will enable users of atomic force microscopes to measure the topographical features of the smallest semiconductors. The discovery involves a new gee-whiz technology, carbon nanotubes.
After reading the Xidex news release I took a virtual stroll on the Internet and found that Xidex and SEMATECH are not alone in their interest in carbon nanotubes. Researchers at companies like IBM
What? You've never heard of carbon nanotubes, or atomic force microscopes? Bear with me while I try to explain why carbon nanotubes have so many people excited. I promise to keep the technical jargon to a minimum, but there may be a quiz at the end, so pay attention.
You probably will agree that in order to understand how carbon nanotubes enhance the atomic force microscope (AFM) we need to understand the operation of an AFM. So here we go.
Prospective applications for nanotube technology
Imagine that you wanted to construct a topographical map of the surface of a semiconductor. It's easy to see how to do this with a section of land because the height variations are big, but for a semiconductor the height variations may be a mere 100 atoms, or even less. An AFM is sensitive enough to measure these tiny height differences.
In an AFM a fine tip is attached to the end of a cantilevered arm. The tip is dragged across the surface of the semiconductor and the arm moves up and down as it encounters the atomic peaks and valleys that make up the surface. It is just like the way an old stereo turntable plays music by reading the peaks and valleys imprinted on a record.
All right, that sounds simple enough, so what is a carbon nanotube? Good question!
A carbon nanotube is basically like an empty paper towel tube, but is made of, well, carbon atoms instead of cardboard. It is hollow in the center and unimaginably thin. In fact, the diameter is as small as one-billionth of a meter, or about 10,000 times thinner than a hair from your head. And they can be made very long compared to their width. The length of a carbon nanotube can be one millimeter or so.
To understand the role of the carbon nanotube in an AFM, imagine dragging the palm of your hand across your keyboard in order to "study" its surface topography. Go ahead and give it a try. I'll pause until you're done.... Okay, you probably didn't feel much detail did you? The palm of your hand is so much bigger than the keys that it prevents you from sensing the fine details. Now try it again, but use your fingertip. Ah, that works much better! Your fingertip is a lot smaller and can detect not only the individual keys, but also the gaps in between.
The carbon nanotube plays the role of your finger. Its width is so small that it can squeeze into the cracks and crevices that are present on the surface of every semiconductor. At the same time it is long enough that it can reach the bottom of deep valleys that conventional tips cannot touch.
Carbon nanotube tips will allow researchers and engineers to conduct much finer measurements during development and manufacture of semiconductor devices. This capability is increasingly important since semiconductor features are being continuously miniaturized in order to satisfy users' demands for more performance and lower prices.
Consumer electronics and homeland defense: next up, a smooth shave
Carbon nanotubes are definitely not limited to lending a helping hand to atomic force microscope users. In the future you may want to toss that "crummy" $5,000 plasma TV into your kid's room to make way for Motorola's nano emissive display. The nano emissive display is Motorola's name for a large flat-panel display based on carbon nanotubes. They aren't available yet, but Motorola claims that they have better image quality and can be produced at lower cost than plasma or LCD screens.
You may also one day find carbon nanotubes inside your computer. Your computer's microprocessor is constructed of billions of tiny circuit elements called transistors. Normally, silicon is used to build the transistors, but in 1998 the first transistor constructed from carbon nanotubes was reported. There are still technical challenges to solve, so you won't find carbon nanotubes inside any of the electronics that you saw on your last visit to Best Buy
One last application that I'll mention is relevant to homeland security. Researchers at General Electric are busying themselves by looking into the use of carbon nanotubes in extremely sensitive sensors for detection of minute traces of biological and chemical agents.
These are just some examples of applications that are currently being developed, but you can be sure that there are many others that have not even been thought of yet.
So has your interest in carbon nanotubes been whetted? Unfortunately, Xidex is not publicly owned, and IBM, GE, Motorola, Mitsui, and DuPont are all too big to be considered anything resembling pure carbon nanotube plays.
If you want to learn about some smaller companies that are publicly owned, and are working in the fascinating new world of nanotechnology, consider a trial subscription to Motley Fool's Rule Breakers.