An In-Situ TEM Study of High Temperature Helium Irradiation of 4H-SiC

SiC is an excellent candidate material for use in fusion and fission nuclear reactors. The work done in this thesis aims to understand the behaviour of SiC under He irradiation at high temperatures. Experiments of helium irradiation in 4H-SiC in temperature range of 700–900°C have been conducted with in-situ ion irradiation facility of MIAMI.
A couple of results are derived from the experiments: The major experimental observations were the formation bubble discs. There is a critical temperature threshold around 700°C above which much higher number density of bubble discs were formed. At 800°C, bubble discs were observed to grow with increasing helium fluence. Growth of bubble discs was also observed when the temperature was held at 800°C after a fluence of 3.8×1016 ions.cm–2 as the bubble discs grew due to diffusion of helium and gain of vacancies. Bubble discs trended to stop growing with a mean size of 30 nm at a fluence of 6.1×1016 ions.cm–2. The evolution of bubble discs was similar at 900°C as at 800°C. Analysis done at room temperature of experiments conducted at 900°C revealed that bubble discs formed preferentially on the {001} and {100} planes.