Defects were introduced into the 6H hexagonal polytype by bombardment with 16MeV protons and 14MeV neutrons. The fluences in both cases ranged from 1015 to 1016/cm2. Combined positron annihilation and low-temperature photoluminescence measurements were used to characterize the resultant defect structure. It was observed that the induced defects gave rise to an intense low-temperature photoluminescence emission and to a corresponding change in the positron lifetime.

N.Hayashi, H.Watanabe, K.Sakai, K.Kuriyama, Y.Ikeda, H.Maekawa, T.Miura: Materials Science Forum, 1995, 196-201, 1243-8