Abstract
We synthesized an ultrapure nano-polycrystalline diamond (NPD) containing very few chemical impurities (<1 ppm). The 13C concentration of the carbon source was reduced to less than 0.01% by using 12C-enriched high-purity carbon. The ultrapure NPD was synthesized by direct conversion from graphite under high-pressure and high-temperature (HPHT) conditions. We measured the optical properties of the ultrapure NPD, which appeared yellowish, attributed to the structural features of the specimen. Also, the one-phonon absorption peak at 1220 cm−1 is attributed to the broken symmetry of the diamond lattice. Moreover, a defect-related PL peak was found at 730 nm.
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