Mechanism of silicon exfoliation induced by hydrogen/helium co-implantation

Infrared spectroscopy and secondary ion mass spectrometry are used to elucidate the mechanism by which co-implantation of He with H facilitates the shearing of crystalline Si. By studying different implant conditions, we can separate the relative contributions of damage, internal pressure generation, and chemical passivation to the enhanced exfoliation process. We find that the He acts physically as a source of internal pressure but also in an indirect chemical sense, leading to the reconversion of molecular ${\mathrm{H}}_{\mathrm{2}}$ to bound Si–H in “${\mathrm{VH}}_{\mathrm{2}}$ -like” defects. We postulate that it is the formation of these hydrogenated defects at the advancing front of the expanding microcavities that enhances the exfoliation process.