Raman Scattering and Electron Spin Magnetism Features in Monocrystalline CVD Diamonds Irradiated with Fast Neutrons

Abstract

The effect of reactor neutron irradiation on Raman scattering spectra and electron spin resonance (ESR) signals of monocrystalline CVD diamond films is studied. The presence of superparamagnetic clusters of spin radicals (ferrons) — regions of magnetic ordering of uncompensated electron spins (g-factor ≈4.65) in an external magnetic field — is revealed for the first time in neutron-irradiated (fluence 3·10¹⁸ cm⁻²) diamonds. It is established that thermal annealing at 400°C for 1 h drastically reduces the ESR signal intensity of spin-radical associates of radiation defects, while approximately doubles the amplitude of the ESR signal from single paramagnetic centers and narrows its linewidth by a factor of ≈4.6. Raman spectroscopy data indicate partial recovery of the crystal structure of diamond due to the annealing of both single radiation defects and nanoscale amorphized regions (ferrons). The types of defects responsible for the formation of ferrons in diamonds as a result of their irradiation with reactor neutrons are discussed.