The role of isolated nitrogen in phosphorescence of high-temperature-high-pressure synthetic type IIb diamonds

Donor-acceptor pair recombination theory was used extensively to explain type IIb diamond phosphorescence mechanism, in which the acceptor was widely believed to be boron, and the donor remained an issue of debate. In this work, 10 pieces of high-temperature-high-pressure synthetic diamonds were studied by using DiamondView (TM), Fourier transform infrared spectroscopy, photoluminescence spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. All the samples presented greenish blue phosphorescence, with emission band centered at 470 nm with a similar to 500 nm shoulder, which can be excited by ultraviolet light with wavelengths from 215 to 240 nm. A neutral isolated nitrogen signal appeared in EPR when the sample was illuminated with a short wave ultraviolet light source. These results helped us to suggest the isolated nitrogen is the most likely donor to generate phosphorescence with boron. (C) 2020 Elsevier Ltd. All rights reserved.