The thermal release of simultaneously implanted H+ and D+ (energies ranging from 0.9 to 10keV per H or D) revealed that the extent of H-D mixing in the form of mixed-isotope H and CH4 molecule emissions depended upon the D+-H+ range separation. This indicated that both H and CH4 molecules were formed at the end of the ion range in the absence of an energetic incident ion beam. Due to a wall contribution to the measured HD signals, it was not entirely possible to rule out the occurrence of atomic diffusion in the implantation layer during thermal release. The amount of CH4 which was emitted during thermal desorption was found to decrease with increasing implantation energy and was approximately inversely proportional to the ion straggling. The dependence of CH4 emission, during the thermal desorption of implanted H+, upon the H+ implantation flux density clearly demonstrated that CH4 molecules were formed during H+ implantation rather than during post-bombardment thermal release. An apparent fluence threshold was found for CH4 emission, and was shown to be directly proportional to ion straggling. No CH4 molecules were emitted below this fluence threshold.

S.Chiu, A.A.Haasz: Journal of Nuclear Materials, 1994, 210[1-2], 34-42