Abstract:
The presence of radiation-induced defects and the high temperature of
implantation are breeding grounds for helium (He) to accumulate and form Heinduced
defects (bubbles, blisters, craters, and cavities) in silicon carbide (SiC). In this
work, the influence of He-induced defects on the migration of strontium (Sr)
implanted into SiC was investigated. Sr-ions of 360 keV were implanted into
polycrystalline SiC to a fluence of 2 × 1016 Sr-ions/cm2 at 600°C (Sr-SiC). Some
of the Sr-SiC sampleswere then co-implantedwith He-ions of 21.5 keV to a fluence
of 1 × 1017 He-ions/cm2 at 350°C (Sr + He-SiC). The Sr-SiC and Sr + He-SiC samples
were annealed for 5 h at 1,000°C. The as-implanted and annealed samples were
characterized by Raman spectroscopy, scanning electron microscopy (SEM),
atomic force microscopy (AFM), transmission electron microscopy (TEM), and
Rutherford backscattered spectrometry (RBS). Implantation of Sr retained some
defects in SiC,while co-implantation ofHe resulted in the formation ofHe-bubbles,
blisters, and craters (exfoliated blisters). Blisters close to the critical height and size
were the first to exfoliate after annealing. He-bubbles grew larger after annealing
owing to the capture of more vacancies. In the co-implanted samples, Sr was
located in three regions: the crystalline region (near the surface), the bubble region
(where the projected range of Sr was located), and the damage region toward the
bulk. Annealing the Sr + He-SiC caused the migration of Sr towards the bulk, while
no migration was observed in the Sr-SiC samples. The migration was governed by
“vacancy migration driven by strain fileds.”
