Scientists Are Producing Bigger CVD Diamonds Faster

Scientists developed away to produce CVD diamonds bigger and faster than current commercial technologies allow, and even found out how to make them colorless, bringing one scientist to claim that, “The diamond age is upon us”.  Researchers at the Carnegie Institution’s Geophysical Laboratory are now producing 10-carat, half-inch (1.27 cm) thick diamonds at a growth rate of 100 micrometers per hour, approximately five times faster than by other CVD technology or HPHT.

The variety of single crystal diamonds produced by the Carnegie high-growth rate CVD process (Photos courtesy Carnegie Institution)

The single-crystal diamonds are created using a chemical vapor deposition (CVD) process and are colorless, transparent from the ultraviolet to infrared wavelengths with their CVD process.

“High-quality crystals over 3 carats are very difficult to produce using the conventional approach,” said Dr 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 results were reported at the 10th International Conference on New Diamond Science and Technology, Tsukuba, Japan, on May 12, and will be reported at the Applied Diamond Congress in Argonne, Illinois, May 18.

Most HPHT synthetic diamonds are yellow, such as Gemesis produces, and most CVD diamonds are brown. Producing colorless diamonds is expensive, limiting its use not only in jewelry as gems, but also in optics and in scientific research.

During their research, last year the team found that HPHT annealing, a process in which materials are treated to make them less brittle and more workable by heating and then cooling very slowly and uniformly, enhances not only the optical properties of some CVD diamonds, but also the hardness.

According to a report by the researchers, using new techniques, the scientists have produced transparent diamonds using a CVD method without HPHT annealing.

To increase the size of the crystals, the Carnegie researchers grew gem-quality diamonds sequentially on the 6 faces of a substrate diamond plate with the CVD process. This way the three-dimensional growth of colorless single-crystal diamonds in the one-inch-range (~300 carat) is achievable, they claim.

The researchers add that while the process they used saw a growth rate of 100 micrometers per hour, growth rates in excess of 300 micrometers per hour have been reached, and 1 millimeter per hour may be possible.

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