Влияние флюенса ускоренных электронов на парамагнитные свойства НРНТ алмазов

The diamond single crystals (10 samples) synthesized by the method of high pressures and high temperatures in the region of the thermodynamic stability of diamond (temperature 1600°C and pressure 5 GPa) by gradual recrystallization of carbon dissolved in the molten metal were investigated. Diamonds were synthesized for 85 hours in two growth systems: Fe – Ni – C and Fe – Al – C. As a result, yellow (type Ib) and colorless (type Ia) crystals were obtained. The samples were investigated by the method of electron paramagnetic resonance. The concentration of paramagnetic centers was determined from the EPR spectra. Registration was carried out in phase with modulation of the magnetic field at room temperature and microwave power values of 0.01, 0.2, 1, 5, and 15 mW, orientation of the external magnetic field H0∥ . For all crystals type Ib, paramagnetic signals from C defect and exchange-coupled nitrogen atoms were recorded, which indicates a high concentration of nitrogen atoms in the samples (5·10^ 17—5·10^19 cm^-3 ). For diamonds of type Ia, the EPR signal was not recorded. Then, the samples were irradiated with accelerated electrons with an energy of 6 MeV in three stages: with a fluence of 3·10^17 el/cm^2 , 9·10^17 el/cm^ 2 and 3·10^18 el/cm^2 . As a result, the yellow diamonds changed color to green, and colorless diamonds turned greenish blue. It was found that for diamonds from type Ib, a sharp increase in the intensity of the signal from the C-defect was observed at a fluence of 3·10^18 el/cm^2 , as well as a change in the saturation power for the central signal component. For irradiated samples of type Ia, only the central component of the EPR signal with g = 2.0024 was recorded, the intensity of which increases with increasing fluence of accelerated electrons, which may be due to the generation of radiation defects.