Decoration of growth sector boundaries with single nitrogen vacancy centres in as-grown single crystal HPHT synthetic diamond
Abstract
Large (> 100 mm3), relatively pure (type II) and low birefringence single crystal diamond can be produced by high pressure high temperature (HPHT) synthesis. In this study we examine a HPHT sample of good crystalline perfection, containing less than 1 ppb (part per billion carbon atoms) of boron impurity atoms in the 001 growth sector and only tens of ppb of nitrogen impurity atoms. It is shown that the boundaries between 111 and 113 growth sectors are decorated by negatively charged nitrogen vacancy centres (NV-): no decoration is observed at any other type of growth sector interface. This decoration can be used to calculated the relative 111 and 113 growth rates. The bulk (001) sector contains concentrations of luminescent point defects (excited with 488 and 532 nm wavelengths) below 1011 cm-3 (10-3 ppb). We observe the negatively charged silicon-vacancy (SiV-) defect in the bulk 111 sectors along with a zero phonon line emission associated with a nickel defect at 884 nm (1.40 eV). No preferential orientation is seen for either NV- or SiV- defects, but the nickel related defect is oriented with its trigonal axis along the <111> sector growth direction. Since the NV- defect is expected to readily re-orientate at HPHT diamond growth temperatures, no preferential orientation is expected for this defect but the lack of preferential orientation of SiV- in 111 sectors is not explained.