Decoration of growth sector boundaries with nitrogen vacancy centers in as-grown single crystal high-pressure high-temperature synthetic diamond

Large (> 100 mm$^3$), relatively pure (type II) and low birefringence single\ncrystal diamond can be produced by high pressure high temperature (HPHT)\nsynthesis. In this study we examine a HPHT sample of good crystalline\nperfection, containing less than 1 ppb (part per billion carbon atoms) of boron\nimpurity atoms in the {001} growth sector and only tens of ppb of nitrogen\nimpurity atoms. It is shown that the boundaries between {111} and {113} growth\nsectors are decorated by negatively charged nitrogen vacancy centres (NV$^-$):\nno decoration is observed at any other type of growth sector interface. This\ndecoration can be used to calculated the relative {111} and {113} growth rates.\nThe bulk (001) sector contains concentrations of luminescent point defects\n(excited with 488 and 532 nm wavelengths) below 10$^{11}$ cm$^{-3}$ (10$^{-3}$\nppb). We observe the negatively charged silicon-vacancy (SiV$^-$) defect in the\nbulk {111} sectors along with a zero phonon line emission associated with a\nnickel defect at 884 nm (1.40 eV). No preferential orientation is seen for\neither NV$^-$ or SiV$^-$ defects, but the nickel related defect is oriented\nwith its trigonal axis along the <111> sector growth direction. Since the\nNV$^-$ defect is expected to readily re-orientate at HPHT diamond growth\ntemperatures, no preferential orientation is expected for this defect but the\nlack of preferential orientation of SiV$^-$ in {111} sectors is not explained.\n