DIAMONDS ARE FOREVER - AND FOR SCIENCE
LIVERMORE, Calif. - Now thanks to Lawrence Livermore NationalLaboratory's high-pressure physics technologies that monitor thewell-being of nuclear weapons, we can explain some mysteries ofmaterials at the center of our planet and understand the formation ofour universe better. And in the near future we may see diamond-encapsulated micro-circuits and semiconductors-or "smart cookware"that controls its own temperature.
Both solid and gaseous materials behave quite differently whenunder extreme pressures: The kinds at the center of the Earth, withina star like the Sun, or during the energy-yield of a nuclear weapon.Oxygen, for example, transforms to a shiny metal under ultra-highpressure.
The Department of Energy's stockpile stewardship program willsomeday simulate the operation of a nuclear weapon withsupercomputers. So scientists must learn how weapon materials behaveunder extreme pressures. Absent underground tests that produce anuclear yield, other high-pressure physics experiments must providethis answer. Remarkable results have been achieved by the Lab'sJagannadham "Jagan" Akella and Sam Weir using diamond anvil celltechnology. They collaborated with Professor Yogesh Vohra andresearch associate Aaron Catledge at the University of Alabama.
Diamonds are strong, hard, good electrical insulators, great heatconductors and they permit radiation-like diagnostic x-rays-to passunhampered through their crystalline structure. Diamonds also canwithstand ultra-high pressures. Polished by a laser-guided processuntil perfectly flat, then fabricated into a diamond anvil, theseprecious stones provide the foundation for technology to measureelectrically the effects of ultra-high-pressure on material samplesranging from hydrogen to berkelium.
But diamonds are relatively small. So an initial challenge is tomake the samples size very small. Even more challenging is adaptinginstrumentation to investigate samples narrower than the width of ahuman hair, placed on a surface smaller than a pin-head, and squeezedunder a pressure several million times the Earth's normal atmosphere.Sometimes the compression reaches the 3.6 million atmospheresestimated at the Earth's center.
A technology for chemical vapor deposition of epitaxial diamondcrystals allows fabrication on diamonds of miniature printed circuitsthat can withstand tremendous pressure, yet yield accurate results."At these extreme pressures, shear stresses would deform any knownmetal. So epitaxial diamond encapsulation is crucial to ensure thatthe instrument probes survive an experiment," Weir said.
The diamond deposition is coupled with Livermore's advanced 3Dlaser pantography system that deposits a precise pattern of lines onnon-flat surfaces. Akella believes this combination paves the way forthe creation of diamond microcircuits, and eventually semiconductorsthat could be used in specialized applications such as spacecraft,where strength, radiation and super heat-conductivity arerequired.
Founded in 1952, Lawrence Livermore National Laboratory is amulti-disciplinary, national security laboratory that applies scienceand technology to the important issues of our time. The Laboratory ismanaged by the University of California for the U.S. Department ofEnergy.
