Using the Wave Nature of Electrons


Electronic Circuits Scale Down

Source: BBC News Sci/Tech
February 8, 2000

Scientists at IBM say they have made a breakthrough which could make it possible to create electronic circuits that can be measured in nanometres - just billionths of a metre across.

The company's research division at San Jose, California, has discovered a way to transport information on the atomic scale that uses the wave nature of electrons instead of conventional wiring.

The new phenomenon, called the "quantum mirage" effect, may enable data transfer within future nanoscale electronic circuits too small to use wires.

"This is a fundamentally new way of guiding information through a solid," said IBM Fellow Donald Eigler, the lead researcher on the project.

"We call it a mirage because we project information about one atom to another spot where there is no atom."

As electronic circuits get smaller and smaller, the behaviour of electrons changes from being particle-like, and described by classical physics, to being wave-like and described by quantum mechanics.

On very small scales, tiny wires do not conduct electrons very well. So quantum equivalents for many traditional functions must be available if nanocircuits are to achieve the desired performance.

But to do this, scientists must learn how to manipulate the strange behaviour of the quantum world.

Quantum corral

To create the quantum mirage, the IBM scientists built a ring of cobalt atoms on a copper surface. The ring of atoms acts as a "quantum corral", reflecting the copper's surface electrons within the ring into a wave pattern predicted by quantum mechanics.

The size and shape of the corral determines the energy states and spatial distribution of the confined electrons. When the IBM scientists placed an atom of magnetic cobalt at one point in the ring, a mirage appeared at another point. The scientists say they detected the same electronic states in the copper electrons surrounding the phantom cobalt atom, even though no magnetic atom was actually there.

The intensity of the mirage was about one-third of the intensity around the "real" cobalt atom.

The operation of the quantum mirage is similar to the way in which light or sound waves are focused to a single spot by optical lenses, mirrors, and parabolic reflectors.

The experiments were imaged using the extraordinary power of the scanning tunneling microscope, the same instrument that enabled researchers to drag individual atoms into the shape of the IBM corporate logo 10 years ago.

Details of the research have been published in the journal Nature.

Gigahertz race

In a separate announcement, IBM says it will shortly unveil a new family of high-speed computer circuits that run at speeds of 3.3 to 4.5 gigahertz, up to five times faster than today's fastest Pentium III chips.

The new design employs conventional silicon transistors, but uses only half the power of a standard high-performance chip.

"Not only are we in the gigahertz era of microprocessors, but we see our way clear to three to four gigahertz in the future," said Randall Isaac, vice president of systems, technology and science at IBM Research.

"One gigahertz will be commercially available within one year - three and four gigahertz will take three to four years to be commercially available."

Not to be outdone, Intel Corp, the world's largest computer chip maker, says its one gigahertz processors will be available commercially even sooner than IBM's technology - probably within the next 12 months.

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