Defect formation in plastically deformed natural Ib, IaAB, IaB, and low nitrogen diamonds

Abstract

The analysis of experimental data on plastically deformed diamonds of different types Ib, IaAB, IaB, and low-nitrogen crystals has been performed. It has been established that the most characteristic defects in plastically deformed diamonds are broken bonds in the dislocation cores. These defects appear in electron paramagnetic resonance (EPR) as a single line with a g-factor of 2.0031 and in luminescence as a vibronic system with a zero-phonon line (ZPL) at 490.7 nm. During plastic deformation, atomic planes slide affecting extended defects such as nitrogen A and B centers, leading to their destruction. For A centers, one of the nitrogen atoms can be displaced by 2.5 Å or greater, forming pairs of impurity atoms separated by two or more carbon atoms. For these paired defects, electron transfer from one of the nitrogen atoms to the broken bonds in the dislocation cores occurs, resulting in the formation of charge transfer complexes. The charge transfer optical band observed in the absorption spectra, which has a maximum at 550 nm, is responsible for the brownish color of these crystals. When the slip planes involve B centers, their destruction leads to the formation of N₃V and C centers. Both the N₃V and C centers exist in a non-paramagnetic state due to the transfer of an electron from the donor nitrogen to the N₃V center. Plastically deformed type IaB crystals are colorless or exhibit a slight bluish tinge due to the formation of N₃V centers. In the case of type Ib diamonds, impurity nitrogen is primarily present in the form of C centers, which act as electron donors for acceptors such as the broken bonds in the dislocation cores. Consequently, for plastically deformed type Ib crystals, the N⁺ nitrogen state is detected, which anneals out at temperatures above 2100 °C, specifically in the temperature range when dislocations are destroyed.