Electron paramagnetic resonance (EPR) and optical absorption studies of defects created in diamond by electron irradiation damage at 100 and 350 K

We present a study, using electron paramagnetic resonance (EPR) and optical absorption spectroscopies, of high purity synthetic type IIa diamonds, which have been irradiated with 2 MeV electrons in a specially developed dewar; allowing irradiation at a measured sample temperature down to 100 K, at doses of 2 x 10(17) --> 4 x 10(18)e(-) cm(-2). The production rate of vacancies (1.53(10) cm(-1)) was the same for irradiation at 100 as at 350 K; as was the production rate of the EPR centre R1, known to be two nearest-neighbour (0 0 1)-split interstitials (0.014(4) cm(-1)). However, the production rate of the (0 0 1)-split self-interstitial (R2 EPR centre) is 1.1(1) cm(-1) at 100 K and only 0.10(5) cm(-1) at 350 K. That R1 is created at 100 K indicates that the self-interstitial is mobile under these conditions of irradiation. Production rates have also been measured for the R3 and R14 EPR centres and a new centre, labelled O3. (C) 1999 Elsevier Science B.V. All rights reserved.