10 Carat Diamond: Credit: Carnegie Institution This 5-carat diamond was laser-cut from a 10-carat single crystal produced by high-growth rate CVD.

If a small diamond is placed in an environment with just the right pressure, temperature, and an atmosphere rich in vaporized carbon, the carbon vapor will start attaching to the surfaces of the "seed" diamond. Layer by layer the diamond will get bigger. Scientists think that growing 300 carat diamonds (one inch) will soon be possible.

Researchers at the Carnegie Institution of Washington, D.C. have produced 10-carat, half-inch thick single-crystal diamonds at rapid growth rates (100 micrometers per hour) using a chemical vapor deposition (CVD) process. The size is approximately five times that of commercially available diamonds produced by the standard high-pressure/high-temperature (HPHT) method and other CVD techniques.

Growing diamonds: Credit: Carnegie Institution Single-crystal diamond block formed by deposition on 6 {100} faces of a substrate diamond, such as the 4 x 4 x 1.5 mm3 crystal shown below.

High-quality crystals more than three carats are very difficult to produce using the conventional approach," said scientist Russell Hemley, who leads the diamond effort at Carnegie. "Several groups have begun to grow diamond single crystals by CVD, but large, colorless, and flawless ones remain a challenge. Our fabrication of 10-carat, half-inch, CVD diamonds is a major breakthrough." The standard growth rate is 100 micrometers per hour for the Carnegie process, but growth rates in excess of 300 micrometers per hour have been reached, and 1 millimeter per hour may be possible.

With the colorless diamond produced at ever higher growth rate and low cost, large blocks of diamond should be available for a variety of applications. “The diamond age is upon us,” concluded Hemley.

Carnegie News release

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