A diamond slab was implanted to doses of 1 x 1017, 2.5 x 1017 and 5 x 1017/cm2 with 600keV and 1MeV 4He+ ions. Results were presented which showed that it was possible to detect the implanted helium by H+ back-scattering spectrometry. A comparison of the Raman spectra and back-scattering spectra of the samples showed that, in cases where the damage introduced by implantation resulted in graphitization and cracking, the implanted helium escaped. When the diamond matrix did not graphitize or crack, no noticeable diffusion occurred and the implant was confined and subjected to pressures of up to 14GPa. Most of the loss of helium was attributed to diffusion through the graphitized region and eventual escape through the cracks.

Effects of Damage on Diffusion of Implanted Helium in Diamond Measured by Nuclear Elastic Scattering. Orwa, J.O., Jamieson, D.N., Nugent, K.W., Prawer, S., Kalish, R.: Nuclear Instruments and Methods in Physics Research B, 1997, 124[4], 515-8