The migration behaviour of strontium co-implanted with helium into SiC at room temperature and annealed at temperatures above 1000 °C

Abstract

The study investigated the migration behaviour of Sr implanted into SiC in the presence of helium (He). Sr ions were implanted into polycrystalline SiC samples (Sr-SiC) at room temperature (RT), and co-implanted with He ions also at RT (Sr + He-SiC). The samples were then annealed isochronally at 1100 ◦C, 1200 ◦C, and 1300 ◦C for 5 h. Transmission electron microscopy (TEM) and Rutherford backscattering spectrometry (RBS) were used to characterize both as-implanted and annealed annealed samples. Sr implantation induced amorphization of SiC, while co-implantation with He led to the formation of He nano-bubbles within the amorphous SiC matrix. During annealing, Sr migrated towards the surface, resulting in loss of Sr, cavity formation, and formation of Sr precipitates in the Sr-SiC samples. In Sr + He-SiC samples, He-induced cavities formed around the projected range of Sr, inhibiting epitaxial regrowth of SiC. As a result, the Sr distribution became concentrated around these He cavities, with Sr trapped both in front and behind them. The enhanced migration of Sr in annealed Sr + He-SiC is attributed to the slower recrystallization of the damaged SiC layer, the presence of larger He-induced cavities, and increased surface roughness. These findings provide insights into Sr migration the mechanisms in SiC, relevant for enhancing the safety of nuclear fuels.