Unusual types of extended defects in synthetic high pressure–high temperature diamonds

New unusual types of extended defects resembling bunches of divergent dislocations are observed in high quality synthetic HPHT single crystal diamonds grown at the lowest possible PT-conditions. Thorough characterisation of the samples by X-ray topotomography, optical microscopy and vibrational spectroscopy allowed the conclusion that these defects are related to dislocations decorated by oxide inclusions. An unusual feature of the defects is their origin: small-angle grain boundaries formed during growth instabilities. Although similar defects were observed in some isostructural materials, their presence in diamonds was not reported earlier.