Effects of helium (He) bubbles and annealing on the structural evolution and migration behavior of silver (Ag) implanted into polycrystalline SiC at 350 °C

The effects of helium (He) bubbles and annealing on the structural evolution and the migration of silver (Ag) implanted into polycrystalline silicon carbide were investigated. Ag ions of 360 keV were implanted into polycrystalline SiC to a fluence of 2 × 10 ¹⁶ cm⁻² at 350 °C (Ag-SiC). Some of the implanted samples were then implanted with He ions of 17 keV to a fluence of 1 × 10¹⁷ cm⁻² also at 350 °C (Ag + He-SiC). The Ag-SiC and Ag + He-SiC samples were then annealed at 1100 °C for 5 h. The as-implanted and annealed samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM), Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). Implantation of Ag resulted in the accumulation of defects in SiC without amorphization. Co-implantation of He resulted in the formation of elongated and tiny He bubbles accompanied by the formation of blisters and holes on the surface. Annealing at 1100 °C resulted in some recovery of the SiC crystal structure, indicating that some defects were annealed out in both Ag-SiC and Ag + He-SiC. This was accompanied by the appearance of more holes on the annealed Ag + He-SiC surface and bigger cavities in the co-implanted SiC layer. Some limited migration of implanted Ag accompanied by the formation of Ag precipitates was observed in the as-implanted Ag + He-SiC sample. No migration of Ag was observed in the annealed Ag-SiC samples while migration of Ag towards the surface accompanied by loss was observed in the annealed Ag + He-SiC sample. The migration of Ag in the annealed Ag + He-SiC was also accompanied by the formation of big Ag precipitates trapped in the cavities. Hence, He bubbles assisted the migration of Ag while cavities trapped the Ag in the Ag + He-SiC samples.