EPR study of Si- and Ge-related defects in HPHT diamonds synthesized from Mg-based solvent-catalysts

this work, high pressure high temperature ( HPHT) diamonds synthesized in the Mg-C system with germanium, silicon and boron additives were studied. In the photoluminescence spectra of the samples doped with Ge, an intense system 602 nm attributed to germanium-vacancy defects was detected. In the electron paramagnetic resonance ( EPR) spectra of these samples, a new paramagnetic center with S = 1 was detected along with substitutional nitrogen P1 and silicon-vacancy KUL1 ( SiV0) centers. The angular dependence investigation of the new spectrum allowed us to establish its spin Hamiltonian parameters: g(parallel to)| = 2.0025, g(perpendicular to) = 2.0027, D = 80.3 mT, E = 0. The center was determined to have the symmetry axis parallel to < 111 >. Hyperfine structure ( HFS) of one Ge-73 atom ( I = 9/2) was observed for the new spectrum. The novel paramagnetic center was proposed to be the neutral germanium split-vacancy defect. EPR and luminescence studies of diamonds doped with Si and B revealed a new paramagnetic center that can be associated with the sharp luminescence system 720 nm. An analysis of the angular dependence of the EPR spectrum showed that it had electronic spin S = 1/2 and anisotropic g-factor: g(1) = 2.0033, g(2) = 2.0004, and g(3) = 2.0024. Based on the principal values and directions of the g-tensor the detected center was suggested to have the structure of silicon and boron atoms in the nearest carbon positions. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim