The displacement of B from substitutional lattice sites during irradiation with a high energy (650keV) proton beam was measured by channelling analyses along the <100> and <110> using the 11B (p,α)8Be reaction. The normalized B yield, χ, increased with the ion fluence and saturates at a value (χF<1) that depends on the channelling axis, being minimum for channelling along <110>. Therefore, displaced B was not randomly located in the lattice. The displacement rate was shown to be consistent with a model involving Si interstitial–B interaction and to depend on the local Si self-interstitial production rate, rather than long range interstitial migration. This was demonstrated by comparing results from samples with and without a Si layer containing 1at%C (known to be a trap for interstitial Si) interposed between the B doped layer and the substrate. The B displacement rate did not change in this sample, indicating that self-interstitials produced at the end of the range did not play a role in this process. It was therefore concluded that only the Si interstitials produced in the B doped layer contributed to the B displacement and the damage rate could be fitted by using the formula: χ = χF- [χF- χ0]*exp(-σ*NI), where χ0 was the χ of the non-irradiated sample and NI was the number of (Si interstitials)/cm2 calculated by TRIM, with σ~10-16cm2.

Cross Section of the Interaction between Substitutional B and Si Self-Interstitials Generated by Ion Beams. A.M.Piro, L.Romano, P.Badalà, S.Mirabella, M.G.Grimaldi, E.Rimini: Journal of Physics - Condensed Matter, 2005, 17[22], S2273-7