Influence of radiation damage on diffusion of fission products in silicon carbide

Abstract

The influence of irradiation induced damage on the transport of implanted species in poly and single crystalline silicon carbide is investigated. For this purpose published diffusion results of strontium, silver, iodine and cesium are compared with the associated evolution of defect profiles determined by α-particle channelling in a backscattering geometry. Strong diffusion takes place in the amorphized surface layer of room temperature implanted 6H-SiC during annealing at 1100 °C, which drops below the detection limit of 10-21 m2 s-1 as soon as re-crystallization is completed. Diffusion in samples implanted above the critical amorphization temperature is only observed when simultaneously a significant reduction of defect density occurs. No diffusion into the undamaged bulk is detected at temperatures up to 1500 °C. The observed diffusion behaviour is explained by a defect related trapping and release mechanism. Normal grain boundary diffusion of silver and iodine occurs in CVD-SiC.