Ionization-induced thermally activated defect-annealing process in SiC

International audienceIonizing events can lead to panoply of irradiation effects, and in silicon carbide (SiC), they drastically modify the defect production rate or the initial density. To better understand this phenomenon, 6H-SiC single crystals were first predamaged using low-velocity 100-keV Fe+ ions at three fluences in the range of 1014cm−2 to induce three different initial disorder levels peaking at values between ∼0.8 and 1 (1 corresponding to full amorphization). Crystals were then submitted to swift heavy ion irradiation in the 1013cm−2 fluence range at both low (∼100 K) and high (∼770 K) temperature. Rutherford backscattering spectrometry in channeling conditions revealed that swift ions allow annealing part of the initial damage, the recovery efficiency increasing with the irradiation temperature and reaching 75% in initially severely disordered crystals. This temperature effect has been qualitatively predicted by molecular dynamics simulations. Transmission electron microscopy allowed imaging both the recovery and the difference in the microstructure of the layers irradiated at low or high temperature. Recovery cross sections are found to lie in the range of a few square nanometers, consistent with previously reported values. A scenario for a general, two-step annealing mechanism referred to as an ionization-activated, thermally assisted defect-annealing (IATADA) process is proposed. This mechanism rationalizes the diverse descriptions reported so far in the literature