Fluence-Dependent Evolution of Paramagnetic Triplet Centers in e-Beam Irradiated Microcrystalline lb Type HPHT Diamond

Paramagnetic triplet centers produced by e-beam irradiation of synthetic microcrystalline Ib-type high-pressure high-temperature (HPHT) diamonds were studied by continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy at X-band (9.4 GHz), pulsed EPR at X- and Q-bands (34 GHz), and fluorescence spectroscopies as a function of radiation fluences up to 5 x 10(19) e(-)/cm(2). EPR spectra of mostly forbidden. Delta m(s) = 2 electronic spin transitions observed at g approximate to 4 (i.e., so-called half-field EPR spectra) reveal the presence of the main W15 triplet defects associated with the fluorescent negatively charged nitrogen-vacancy (NV-) centers as well as additional triplet spin centers identified as W16, W17, W18, and W33 that appear upon increasing the e-beam fluence. Consequent annealing at 1,400 degrees C significantly reduces the content of W17, W18, and W33 but not W15 and W16 defects. The efficacy of NV- center fabrication as a function of fluence dependent e-beam irradiation is also reported.