The mechanisms of surface exfoliation in H and He implanted Si crystals

We report on the exfoliation mechanisms in light gas implanted Si. Microstructure characterization, extensive statistical analysis and solid mechanics theory show that exfoliation is caused by microcracks growing close to equilibrium pressure for high fluences. For lower fluences, cracks evolve at under-equilibrium pressure and exfoliation relies on a coalescence mechanism assisted by cleavage. This provides long-range, collective and efficient stress relief for clusters of cracks, causing enhancement of the exfoliation. The physical processes are independent of the irradiation energy.