Tuning the structural properties of cesium-implanted SiC at high temperature under a helium atmosphere

Silicon carbide (SiC) is an important material for nuclear applications, serving as cladding in fission reactor fuels and proposed for the first wall/blanket of fusion reactors, environments where significant helium (He) generation occurs. Therefore, understanding the influence of annealing atmospheres on the structural and surface properties of SiC is essential. In this study, SiC samples were implanted with 300 keV cesium (Cs) ions of a fluence of 1 × 1016 cm−2 at 600 °C. The as-implanted samples were subsequently subjected to sequential isochronal annealing in vacuum and He atmospheres at different temperatures. The results indicate that Cs implantation at 600 °C induced tensile stress and generated lattice defects without causing complete amorphization of SiC. Subsequent annealing in vacuum at higher temperatures (≥800 °C) effectively promoted defect recovery with no detectable migration or loss of Cs atoms, while the surface morphology and roughness remain largely unchanged. In stark contrast, annealing in a He atmosphere led to significant surface alterations, including the growth of whisker-like features and the formation of an oxide layer due to the reaction of trace oxygen impurities with SiC to form silicon dioxide. These whiskers and surface oxides affected Rutherford backscattering spectrometry (RBS) measurements, causing Cs to appear at greater depths than its actual distribution. Overall, these findings demonstrate that the annealing atmosphere critically influences the structural and surface evolution of implanted SiC. Similarities and differences in structural and chemical integrity of SiC during sequential isochronal annealing in vacuum and He will be discussed in terms of the material performance and the apparent depth profiles of implanted species in SiC.