The (100) Si was dual-implanted with the ions Pb+/22Ne+ (7 and 30keV), Pb+/16O+ (7 and 26keV) and Pb+/14N+ (7 and 24keV) to peak concentrations of typically 10 at.%. The implanted samples were then electron beam annealed at 900C for 30 s with a temperature gradient of 5C/s under high vacuum conditions. Channelled RBS measurements performed with 1.5MeV 4He+ ions showed that annealing of the Pb/Ne and Pb/O samples resulted in an almost complete recrystallisation of the amorphous layers caused by the ion implantations and a total loss of the implanted Pb. For the Pb/Ne samples the Ne diffused out to leave a rough surface sprinkled with deep craters; for the Pb/O samples some SiO2 formed below the surface. In contrast, for the Pb/N samples most of the amorphous layer survives annealing and almost all the Pb was retained. A striking feature was that annealing causes the Pb to diffuse away from the surface to be trapped in a deep diffusion sink provided by the implanted N. X-ray diffraction analyses revealed Pb (111) and Pb (220) . reflections, suggesting that Pb nanoclusters had grown in the sub-stoichiometric silicon nitride layer. These structures offered an interesting opportunity for controlled carbon nanotube growth on silicon nitride.

Diffusion of Pb in (100) Si under Electron Beam Annealing Following Dual Ion Implantations of Pb/Ne, Pb/O and Pb/N. A.Markwitz, F.Fang, H.Baumann, P.B.Johnson: Vacuum, 2010, 84[9], 1103-10