Temperature and dose dependence of ion-beam-induced amorphization in alpha-SiC

Single crystal alpha-SiC with [0001] orientation has been irradiated at 170, 300, and 370 K with 360 keV Ar2+ ions at an incident angle of 25 degrees and the damage accumulation process followed in situ by Rutherford backscattering spectroscopy in channeling geometry (RBS/C) along [1 (1) over bar 02]. At 170 and 300 K, the increase in relative disorder with ion fluence, as measured by RBS/C, is consistent with a multiple-cascade overlap process. Then is a significant deviation from the cascade overlap model at 370 K. The RBS/C results indicate that below a critical damage level the relative disordering rate is nearly temperature independent. Post-irradiation characterization of the fully disordered samples indicate a significant loss in the intensity of the Raman modes and decreases of 47 and 24% in hardness and elastic modulus, respectively, Cross sectional transmission electron microscopy has confirmed the amorphous nature of the damaged surface layer irradiated at 170 K; however, at 370 K, some residual crystallinity was observed over the depth range from 10 to 160 nm. The decrease in density associated with amorphization at 170 K is estimated to be 22 +/- 3%.