Point Defects in Natural and Synthetic Diamond: What They Can Tell Us about CVD Diamond

More than 30 years of research on point defects in natural and high pressure, high temperature (HPHT) synthetic diamond helps us to characterise diamond produced by chemical vapour deposition (CVD). Nitrogen is the most common impurity in natural diamond, but hydrogen and boron are also detected. In HPHT diamond, nickel or cobalt complexes are seen as well. Irradiation produced interstitials and vacancies, which can help to identify some native defects. CVD diamond also may contain nitrogen and boron. A prominent defect, not normally seen in natural diamonds, is due to a silicon–vacancy complex. There are some hydrogen-related lines in the EPR spectra, which are peculiar to polycrystalline diamond and appear to arise near grain boundaries. Vacancies are seen close to the growth surfaces of particularly good quality CVD diamonds, although they are not present in the bulk of the diamond. Experience of vacancy migration in natural diamond allows us to explain this phenomenon.