Effects of damage on diffusion of implanted helium in diamond measured by nuclear elastic scattering

A diamond slab was implanted to doses of 1 × 1017, 2.5 × 1017 and 5 × 1017 cm-2 with 600 keV and 1 MeV 4He+ ions. We present results which show that it is possible to detect the implanted helium by H+ Backscattering Spectrometry (BS). A comparison of the Raman spectra and BS 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 14 GPa. We attribute most of the loss of helium to diffusion through the graphitized region and eventual escape through the cracks.