The vacancy–hydrogen defect in diamond: A computational study

Abstract

Hydrogen is grown into CVD diamond and occurs in point defects also involving a lattice vacancy, V . Complexes involving V , H and nitrogen, or silicon have been identified by experiment, and in some cases the microscopic structure has been identified with the use of quantum-chemical simulations. In this study, we present the results of density functional simulations of the primitive vacancy-hydrogen defect in diamond. We find that the symmetry of the V H defect is C 3v , with the H atom strongly bonded to one of the four C radicals that are formed when the vacancy is created. The defect is expected to occur in both the neutral and negatively charged forms, with the possibility of both positive and −2 charge states. For V H 0 , S = 3/2 and S = 1/2 spin states are found to be indistinguishable in energy, with the quartet not expected to yield sharp optical transitions, unlike the doublet. V H −1 in the S = 1 ground-state is predicted to have an optical transition that is broadly similar to that of NV − (S = 1), although it is important to note that the non-degenerate band involved in the transitions arises from a different origin in V H −1 as there are no lone-pairs present in this case. We have also made predictions for the C-H stretch mode frequencies, noting a general trend with charge state. Combinations of optical spectroscopy, paramagnetic resonance and vibrational mode spectroscopy are therefore required to fully experimentally resolve V H in its various charge and spin states.

Nitrogen in Diamond

“…418 The defect has an S = ½ ground state and, as with NVH ( §3.5.5.1), the hydrogen atom is found to re-orientate between the equivalent carbon bonding locations at a rate that is fast compared to the EPR timescale, leading to a time-averaged rhombic C2v symmetry (Figure 32(b)), as opposed to the static C1h symmetry. 419,420 Nitrogen isotopic substitution confirms the presence of nitrogen in the defect. Table 3 collects together the hyperfine parameters, percent unpaired-spin density localised on each N atom, and the principal quadrupole parameter for the various EPR-measured NnV and NnVH defects.…”

Di‐nitrogen–vacancy–hydrogen defects in diamond: a computational study

“…In general, both N and H are grown into defects in CVD diamond individually , so, in particular that N‐aggregates are not seen in as‐grown samples. However, defects involving vacancies are known to contain both H and N , with the N V H centre being electrically and optically active as a consequence of the unsaturated carbon bonds. The 3107 centres can be formed in CVD diamond via high‐temperature anneals , so it seems likely that structures intermediate between N V H and NH will be formed too, at least transiently.…”

Quantum Point Defects for Solid‐State Laser Refrigeration

“…However, plasma based growth also introduces hydrogen within the diamond crystal lattice, [ 184,185 ] leading the possibility of nonradiative color centers that may also serve as a source of background absorption. [ 186 ] Furthermore, twinning defects [ 187 ] have been observed in diamond materials growth through plasma deposition [ 169 ] and must also be considered when determining potential sources of background absorption.…”