The transport behaviour of strontium and iodine through single and polycrystalline SiC wafers was investigated using ion beam analysis and electron microscopy. Fluences of 2 x 1016Sr+cm−2 and 1 x 1016I+cm−2 were implanted at temperatures between 23 and 600C with an energy of 360keV, producing an atomic density of approximately 1.5% at the projected ranges of about 120 and 90nm, respectively. The broadening of the implantation profiles and its dependence on implantation parameters was determined by isochronal and isothermal annealing studies at temperatures up to 1400C. The strong influence of radiation damage on diffusion after room temperature implantations was observed in all cases during the initial annealing stages at 1000C. This was a result of the highly disordered crystal lattice, which re-crystallizes at this temperature. In hot implantations this effect was largely reduced but an additional transient diffusion process was observed at 1400C for strontium, which was related to defect annealing. Impurity trapping by extended defects was obviously an important effect. Volume diffusion was below the present detection limit of 10−21m2/s for both diffusors. Hence, grain boundary diffusion was responsible for the observed iodine transport in CVD-SiC at 1300C, while no significant diffusion of strontium was detected at 1400C.

Influence of Radiation Damage on Strontium and Iodine Diffusion in Silicon Carbide. E.Friedland, N.G.Van der Berg, J.B.Malherbe, E.Wendler, W.Wesch: Journal of Nuclear Materials, 2012, 425[1-3], 205-10