E.P.R. studies of type IIa diamond, electron irradiated at liquid-nitrogen temperature

A natural type IIa diamond has been irradiated with 2 MeV electrons to a dose of 4 × 1013 electrons cm-2 at approximately 80 K. The E.P.R. spectrum measured immediately after irradiation showed the W-6 system and some unanalysed structure. It was unchanged by pulse annealing to room temperature, indicating that it is unlikely that a defect is mobile in this temperature range. However, measurements of the temperature dependence of the spectrum showed that W-6 is homogeneously broadened and unobservable by room temperature. The R-3 system was seen at 100 K, and its intensity increased with temperature. It is deduced that the R-3 system arises from an excited state. Tentative models for these defects are discussed in terms of interstitial-impurity complexes.