In previous work we showed that the movement of Pb in N/Pb and C/Pb dual-implanted Si under electron beam annealing (EBA) has unexpected features^1,2. This contribution is the first report of the temperature dependence of the novel features. (100) Si was dual-implanted with 24 keV N ions and then with 7 keV Pb ions to give peak concentrations of typically 10 at.%. The centre of the implanted Pb profile was at a depth of 10 ± 1 nm. The implanted samples were treated using EBA for 30 s at a peak temperature, T, ranging from 100 °C to 900 °C. Pb depth profiles were determined using RBS. For values of T up to 500 °C there is no detectable shift in the Pb profile. However, for 600 °C the profile has moved to a depth of 40 ± 2 nm and for 700, 800 and 900 °C the Pb is located at a depth of 68 ± 3 nm, where it is trapped in a deep diffusion sink provided by the N implantation. A striking feature is that despite these large movements away from the surface the width of the Pb profile shows very little broadening. Results presented highlight the sensitive dependence of the response to EBA on i) the order in which the ions are implanted, ii) increasing T to 1000 °C, and iii) the structure of the Si prior to treatment. In (100) Si a correlation has been found between the movement of Pb away from the surface and the formation of nanowhiskers at the surface.

1.   A. Markwitz, F. Fang, H. Baumann, P. B. Johnson, Vacuum 9 (2010) 1103

2.   A. Markwitz, H. Baumann, P. Davy, P. B. Johnson, Vacuum 82 (2008) 1306