Vacancy clusters created via room temperature irradiation in 6H-SiC

In non-annealed 6H-SiC samples that were electron irradiated at low temperature, a new EPR signal due to a S =1 defect center with exceptionally large zero-field splitting (D= +652104cm1,E=8104cm1) has been observed under illumination. A positive sign of D demonstrates that the spin–orbit contribution to the zero-field splitting exceeds by far that of the spin–spin interaction. A principal axis of the fine-structure tilted by 59 1 against the crystal c -axis as well as the exceptionally high zero-field splitting D can be qualitatively understood by the occurrence of additional close-lying defect levels in defect clusters resulting in comparatively large second-order spin–orbit coupling. A tentative assignment to vacancy clusters is supported by the observed annealing behavior.