Cathodoluminescence from high-pressure synthetic and chemical-vapor- deposited diamond

The nature of an UV cathodoluminescence band, which can appear in both boron-doped high-pressure high-temperature (HPHT) synthetic diamond and boron-doped diamond grown by chemical-vapor-deposition (CVD) techniques, is investigated. The band has a peak energy at 4.6 eV (270 nm), a full width at half-maximum of ∼0.4 eV and at low temperatures (∼130 K) can represent the overwhelmingly dominant cathodoluminescence (CL) from selected regions of a given sample. The band has been examined from boron-doped HPHT diamond grown from different solvent catalysts and from boron-doped CVD diamond grown under a variety of deposition conditions. Low-temperature spatially resolved CL imaging, using a scanning electron microscope with CL attachment, has revealed a clear growth-sector dependence of the 4.6 eV band in HPHT diamond. Using this technique an investigation of the relationship between this band and other commonly observed CL bands has been carried out. The band has an interesting temperature dependence which is investigated over the temperature range 77-300 K and explained in terms of competition between exciton capture and exciton release at some unidentified trapping center.