Effect of irradiation on the properties of nanocrystalline silicon carbide films

The effect of irradiation with electrons on the optical and electrical properties of the nanocrystalline rhombohedral 21R-SiC and 27R-SiC films is studied. The cycles of irradiation of nanocrystalline SiC films on sapphire substrates with electrons with the energy 10 MeV are conducted in the range of fluences from 5 × 1014 to 9 × 1019 cm−2. It is established that, at the irradiation doses above 1019 cm−2, the optical absorption of the films at the photon energies E > Eg becomes less efficient than the optical absorption of unirradiated films. It is established that the Urbach energy as a function of the irradiation dose exhibits a minimum at the dose ∼1017 cm−2 for the 21R-SiC films and ∼5 × 1017 cm−2 for the 27R-SiC films, suggesting that radiation induces some ordering in the films. As the dose is increased from 5 × 1017 up to 9 × 1019 cm−2, an increase in the Urbach energy and a decrease in the optical band gap are observed. The effect is attributed to an increase in the concentration of radiation defects in the films.