Chemical vapor deposited diamond with versatile grades: from gemstone to quantum electronics

Chemical vapor deposited (CVD) diamond as a burgeoning multifunctional material with tailored quality and characteristics can be artificially synthesized and controlled for various applications. Correspondingly, the application-related “grade” concept associated with materials choice and design was gradually formulated, of which the availability and the performance are optimally suited. In this review, the explicit diversity of CVD diamond and the clarification of typical grades for applications, i.e., from resplendent gem-grade to promising quantum-grade, were systematically summarized and discussed, according to the crystal quality and main consideration of ubiquitous nitrogen impurity content as well as major applications. Realizations of those, from quantum-grade with near-ideal crystal to electronic-grade having extremely low imperfections and then to optical, thermal as well as mechanical-grade needing controlled flaws and allowable impurities, would competently fulfill the multi-field application prospects with appropriate choice in terms of cost and quality. Exceptionally, wide range defects and impurities in the gem-grade diamond (only indicating single crystal), which are detrimental for technology applications, endows CVD crystals with fancy colors to challenge their natural counterparts.