The radiation damage which was caused to polycrystalline films by 2MeV alpha particles was studied as a function of the irradiation dose (1012 to 1017/cm2). The films were characterized by using Raman and photoluminescence spectroscopy and I-V measurements. The results showed that, in undoped samples, the H3 luminescent center (N-V-N) was observed at doses greater than 1014/cm2. The Raman diamond peak broadened, and shifted to lower frequencies, at doses of more than 1015/cm2. No new graphitic component was detected after irradiation. In fact, graphitic sp2 defects were annealed out by the irradiation. At a dose of 3 x 1016/cm2, new Raman defect peaks were detected at 1496 and 1635/cm. The I-V characteristics were unaffected by doses of less than 1016/cm2. An increase in the conductivity was observed at a dose of 3 x 1016/cm2. At this dose, an activation energy of 0.4eV was observed as well as thermally stimulated currents that were related to defect levels at about 0.3eV. A B-doped sample was irradiated to a dose of 1017/cm2 for comparison. After irradiation, the conductivity of this sample was reduced; as was the activation energy for conduction. Less damage was detected, by Raman spectroscopy, in the B-doped material.

P.Gonon, S.Prawer, K.W.Nugent, D.N.Jamieson: Journal of Applied Physics, 1996, 80[9], 5006-13