Spectroscopic study of defects and inclusions in bulk poly- and nanocrystalline diamond aggregates

Recently, a novel form of nanodiamond exhibiting unusual mechanical properties has been synthesized by high-pressure high-temperature (HPHT) treatment of C60 fullerene, amorphous carbon and diamond powder. In this study, we have characterized the dominant defects in this nanodiamond by a combination of optical absorption, luminescence, Raman, electron spin resonance and elastic recoil detection techniques. Unusually high concentrations (~0.4 at.%) of hydrogen and very low concentrations of nitrogen (~1E-5 at.%) have been detected in diamond grown from C60. Although most of hydrogen is shown to originate from inclusions of foreign phases, such as water, significant concentrations (~0.01 at.%) of hydrogen were also detected as a point defect in the nanodiamond grains. Observed structural differences between the samples made from various carbonaceous materials are attributed to different behaviour of the starting compounds during HPHT treatment.