6H-SiC and 3C-SiC single crystals were
simultaneously irradiated at room temperature with 100 keV Fe ions at fluences
up to 4 × 1014 cm−2 (~0.7 dpa), i.e. up to amorphization. The disordering
behaviour of both polytypes has been investigated by means of Rutherford
backscattering spectrometry in the channelling mode and synchrotron x-ray
diffraction. For the first time, it is experimentally demonstrated that the
general damage build-up is similar in both polytypes. At low dose, irradiation
induces the formation of small interstitial-type defects. With increasing dose,
amorphous domains start to form at the expense of the defective crystalline
regions. Full amorphization of the irradiated layer is achieved at the same
dose (~0.45 dpa) for both polytypes. It is also shown that the
interstitial-type defects formed during the first irradiation stage induce a
tensile elastic strain (up to ~4.0%) with which is associated an elastic
energy. It is conjectured that this stored energy destabilizes the current
defective microstructure observed at low dose and stimulates the formation of
the amorphous nanostructures at higher dose. Finally, the disorder accumulation
has been successfully reproduced with two models (namely multi-step damage
accumulation and direct-impact/defect-stimulated). Results obtained from this
modelling are compared and discussed in the light of experimental data.
Source:IOPscience
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