Silicon cages metal atoms

By Eric Smalley, Technology Research News

Silicon may be the single most important element in computer chips and electronic devices, but carbon has stolen the spotlight in recent years because of its ability to form complex structures like nanotubes.

A team of researchers at the Joint Research Center for Atom Technology (JRCAT) in Japan has shown that, with a little help from metal, silicon can also form complex shapes. The researchers have encapsulated individual metal atoms in cages of silicon.

Combining silicon's well-known electrical properties with its newfound forms could produce useful characteristics like superconductivity. Individual silicon cage clusters could also be used as quantum bits in quantum computers.

The researchers made the cages by vaporizing metal, suspending the metal atoms in an ion trap and exposing the metal atoms to a silicon gas. Like pearls forming around grains of sand, silicon atoms encapsulated the metal atoms, said Hidefumi Hiura, now a research scientist at NEC Corporation.

The researchers have made silicon cage clusters that encapsulate tungsten, hafnium, tantalum, rhenium and iridium atoms. The clusters form basket- and hexagonal-shaped cages.

This new type of metal-silicon hybrid material could be used to make microelectronics components like the wires and transistors of a computer chip.

The silicon cage clusters are also good candidates for use as quantum computing bits, or qubits, especially because so much of today's computer manufacturing processes are designed to produce silicon components.

The most important quality of a qubit is that it can remain in the quantum state of superposition long enough for a quantum computer to manipulate it the thousands of times necessary to implement a quantum algorithm. The qubit has to remain isolated from its environment in order to be in a superposition of its possible states.

The metal atoms in the silicon cage clusters would likely be stable enough to use as qubits because of the structure itself would serve to isolate the qubits from the environment, said Hiura. "Silicon cage clusters may function as spin qubits in a silicon-based quantum computer," he said. "Their cage structures will serve as both a spin carrier and isolator."

The researchers are working on producing large enough amounts of the cage clusters to test their properties as materials, said Hiura. "The silicon cage clusters may be incorporated into some real devices within several years," he said.

Hiura's research colleagues were Takehide Miyazaki and Toshihiko Kanayama of JRCAT. They published the research in the February 26, 2001 issue of Physical Review Letters. The research was funded by the New Energy and Industrial Technology Development Organization, Advanced Industrial Science and Technology and JRCAT, all of Japan.

Timeline:   < 3 years
Funding:   Government
TRN Categories:   Semiconductors and Materials
Story Type:   News
Related Elements:  Technical paper, "Formation of Metal-Encapsulating Si Cage Clusters," Physical Review Letters, February 26, 2001


March 14, 2001

Page One

Tools cut data down to size

Ribbons expand nanotech toolbox

Silicon cages metal atoms

Surfaces channel liquids

Chip impurities make quantum bits


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