The irradiation-induced crystalline-to-amorphous phase transition in alpha-SiC

The ion-beam-induced crystalline-to-amorphous phase transition in single crystal alpha-SiC has been studied as a function of irradiation temperature. The evolution of the amorphous state has been followed in situ in specimens irradiated with 1.5 MeV Xe+ ions over the temperature range from 20 to 475 K using the HVEM-tandem facility at Argonne National Laboratory. Specimens also have been irradiated at 170 and 370 K with 360 keV Ar+ ions, acid the damage accumulation process followed in situ by Rutherford backscattering spectroscopy in channeling geometry using dual-beam facilities at Los Alamos National Laboratory. The displacement dose for complete amorphization in alpha-SiC at 20 K is 0.25 dpa and increases with temperature in two stages, The simultaneous recovery process associated with the high-temperature stage(above 100 K) has an activation energy of 0.12 +/- 0.02 eV. The critical temperature above which amorphization does not occur is 485 K under these irradiation conditions. Dechanneling results are consistent with disordering occurring by the local accumulation of defects and show a decrease in disordering rate with increasing temperature.