Big Blue has developed a way to use a combination of chip patterns and chemical bonding to precisely place carbon nanotubes on computer chips. Here's a look at some of the technology involved.
Solution of carbon nanotubes
In this dark solution, IBM makes use of carbon nanutubes -- very small structures made of a lattice of carbon atoms rolled into a cylindrical shape. A team of eight researchers have figured out a way to precisely place them on a computer chip, IBM announced today. The new technique helps improve the nanotubes' chances in the hunt for alternatives once silicon transistor technology, the beating heart of today's, runs out of steam.
The dark lines are carbon nanotubes that sometimes -- but not always -- are placed in trenches. The more accurately IBM can place the nanotubes, the more likely they can be used as semiconductor devices in computer chips. The density of carbon nanotubes shown here permits a billion per square centimeter.
In this close-up image, the very thin black lines are carbon nanotubes that span the gap between two electrical contacts. IBM strives to get only a single nanotube in each of the channels, visible as white outlines.
IBM's silicon wafers have two surfaces on top, hafnium oxide and silicon dioxide. This close-up image shows speckles of carbon nanotubes that bond only with the hafnium oxide, part of IBM's approach to positioning them precisely on a chip.
IBM researcher Hongsik Park looks over a chip wafer with carbon nanotubes. The wafer has two surfaces, trenches made of hafnium oxide that attract carbon nanotubes in a special solution silicon oxide that doesn't.
IBM's technique can arrange single carbon nanotubes -- and sometimes pairs -- between two electrical contacts. It's an essential part of making a transistor in which a nanotube leads from a source on one side to a drain on the other. At left in this is an image of a chip designed to test the technology electrically; at right is a close-up of the nanotubes stretching from one electrical contact to another.
The chickenwire-like lattice of carbon atoms just one atom thick is called graphene, one candidate for a new chip semiconductor material. Another is a cylindrical configuration called a carbon nanotube. A 60-atom sphere is called a buckyball. Many sheets of graphene makes graphite, the form of carbon used in pencil lead.