Multicarat colorless single-crystal diamond has been produced using chemical vapor deposition techniques by researchers from Carnegie. The paper is featured on the frontispiece of a recent issue of Physica Status Solidi (a).

Diamond is a unique material with multiple superlative properties. For example, diamond is the ultimate material for many extreme environments and is a crucial element for high P-T experiments. However, the full potential of diamond for numerous applications has not been realized because material of sufficient size and perfection has not been available.

Yufei Meng and colleagues have refined microwave plasma assisted chemical vapor deposition (MPCVD) techniques to produce large, high-purity single crystal diamond anvils. Specifically, multicarat single crystal diamond has been produced at high growth rate without annealing (around 50 µm/h) with low impurity content. The example shown in the image is a 2.3 carat colorless CVD diamond anvil which was cut from crystal 13.5 carat block.

UV-visible absorption, Raman/photoluminesence spectroscopy, cathodolunminesence, and confocal Raman imaging were used to characterize the diamond. The measurements show that the material has a high optical quality and clarity without layers. The large intensity ratio of the second-order Raman peak to the fluorescence background is essential for high-pressure optical windows.

The present results create the prospects for rapid growth, high optical quality single-crystal CVD diamond anvils over 1 carat to be routinely fabricated. The material is an excellent optical window, thereby extending applications of CVD diamond for high-pressure research and other areas of science and technology [Y. Meng, et al., Phys. Stat. Sol. (a) 209, 101-104 (2012)].