“High-quality crystals over 3 carats are very difficult to produce using the conventional approach,” commented 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 diamond is yellow and most CVD diamond is brown, limiting their optical applications. Colorless diamonds are costly to produce and so far those reported are small. This situation limits general applications of these diamonds as gems, in optics, and in scientific research. Last year, the Carnegie researchers found that HPHT annealing enhances not only the optical properties of some CVD diamond, but also the hardness [1]. Using new techniques, the Carnegie scientists have now produced transparent diamond using a CVD method without HPHT annealing.
To further 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. By this method, three-dimensional growth of colorless single-crystal diamond in the inch-range (~300 carat) is achievable.
Finally, new shapes have been fabricated with the blocks of the CVD single crystals.
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 mm 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.
There have been many diamonds in history that have been unique due to size, actual history, and the story behind its journey.
SOURCE: Adapted from a Eurekalert News Release
Diamonds have some advantages over crystaline silicon for semiconductor wafers, right?
Diamond has a thermal conductivity significantly higher than copper or silver. When used as a semiconductor, circuits could be packed much denser than current semiconductor technologies allow. Thermal control is a major issue in integrated circuit design.