Creating NV$^-$-defects in silicon carbide 6$H$–SiC by irradiation with high-energy electrons

The possibility of creating negatively charged nitrogen-vacancy defects (NV$^-$) in crystals of hexagonal (6$H$) silicon carbide by irradiating the latter with high-energy electrons ($E$ = 2 MeV) and subsequent high-temperature annealing at $T$ = 900$^\circ$C was investigated. Using electron paramagnetic resonance (EPR) it was shown that SiC crystals contain triplet ($S$ = 1) centers of axial symmetry with fine structure parameters $D$ = 1344, 1318 and 1268 MHz. The corresponding components of the fine structure are split by a spectrally resolved hyperfine interaction with the nuclear spin of nitrogen ($^{14}$N, $I$ = 1), which is characterized by a hyperfine interaction constant $A\approx$ 1.23 MHz, which makes it possible to unambiguously identify the presence of NV$^-$-centers in the samples under study. It is shown that optical excitation by an IR laser $\lambda$ = 980 nm leads to the creation of an inverse population of the spin sublevels of these triplet centers, which is the basis for their use as quantum sensors, qubits and masers with optical pumping.