Low-temperature investigations of ion-induced amorphisation in silicon carbide nanowhiskers under helium irradiation

The abundant free surface in nanoporous materials may play a major role in providing ideal sinks for the removal of radiation-induced defects. To study the response of these materials to radiation damage, 4H-silicon carbide (SiC) nanowhiskers (NWs) have been used to model individual ligaments of nanoporous SiC. Using in-situ transmission electron microscopy (TEM) with helium ion irradiation, a crystalline-to-amorphous transformation of the nanowhiskers was investigated as a function of irradiation dose and temperature. For a comparative analysis, the NWs were irradiated simultaneously alongside SiC thin foils (model systems for bulk-like SiC) using 6 keV He ions at temperatures between 100 and 400 K and doses up to 50 dpa. Relatively-low swelling (~8%) due to amorphisation was detected in the NWs compared to the foils (~14%) irradiated at room temperature. A relatively-high critical dose for amorphisation (5 dpa) was observed in the NWs for irradiations below room temperature compared to the foils (0.7 dpa). Amorphisation was completely avoided for NWs irradiated above 200 K – lower than the critical temperature in the foils which was ~300 K. The reduced swelling, higher critical-dose and lower critical-temperature for amorphisation exhibited by the NWs indicate an enhancement in radiation resistance over the foils.