In Situ Study of the Temperature Dependence of Irradiation-Induced Amorphization in A-Sic

Abstract

Ion-beam-induced amorphization in single crystal α-SiC has been studied as a function of temperature. Specimens have been irradiated with 1.5 MeV Xe⁺ ions over the temperature range from 20 to 475 K using the HVEM-Tandem Facility (ANL), and the evolution of the amorphous state has been followed in situ in the HVEM. Specimens also have been irradiated at 170, 300, and 370 K with 360 keV Ar⁺ ions, and the damage accumulation process followed in situ by Rutherford backscattering spectroscopy/channeling using the dual beam facilities at the Ion Beam Materials Laboratory (LANL). At 20 K, the displacement dose for complete amorphization is 0.25 dpa and increases with temperature in two stages. The activation energy associated with the simultaneous recovery processes above 100 K is 0.12 ± 0.02 eV. The critical temperature above which amorphization does not occur is 485 K under the 1.5 MeV Xe⁺ irradiation conditions. Ion channeling results suggest that the rate of simultaneous recovery increases with temperature only above a critical damage level. Raman spectroscopy indicates that rapid chemical disordering occurs during irradiation.