POINT PARAMAGNETIC DEFECTS IN DIAMOND IRRADIATED BY HIGH-ENERGY IONS

The spectra of paramagnetic centers (PC) O1 and R5 are observed in natural diamond samples irradiated by high‐energy (> 1 MeV/a.m.u) ions. Both PC are the prevailing paramagnetic point centers in the annealing temperature range of 600 to 1100°C. It is shown that the paramagnetic centers O1 are produced practically completely due to inelastic ion collisions. It is found that the spin‐Hamiltonian parameters of the paramagnetic centers O1 and R5 depend on the annealing temperature. The dependence is probably related to the modification of the crystal local strains as a result of the annealing. In the cathodoluminescence spectra of the investigated samples the narrow zero‐phonon lines (ZPL) ≈511.5 and ≈509 nm are observed. The annealing kinetics and the depth distribution profiles of their intensities are similar to those of the PC O1 ones. It is suggested, that one of these lines is the optical analogue of PC O1. The 〈100〉 Frenkel pair (Ci + V) is proposed as the model of PC O1. The epuilibrium geometry of the Ci + V center in the neutral charge state is theoretically calculated by the CNDO/2 method using the cluster approximation. Relaxation of the atoms of the first coordination sphere is taken into account. The localisation of the C1 atom along the 〈100〉 axes is found to be more energy profitable than that along the 〈111〉 axes. The distance between the vacancy center and the interstitial atom position in the equilibrium configuration of the defect is about 0.02 nm. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA