Abstract
Si single crystals were implanted in a random direction at a temperature of 835 K with 150 keV Pb + ions to a fluence of 1.10 20 m -2 corresponding to a mean implantation depth of about 60 nm and an average concentration of 2-3 at%. The implanted samples have been studied by Rutherford Backscattering (RBS)/channelling and transmission electron microscopy (TEM) techniques. The RBS analysis showed that in as-implanted samples the main fraction of implanted Pb was located on substitutional sites in the Si matrix thus providing a highly supersaturated solution of Pb in Si. Spontaneous precipitation of Pb, giving rise to formation of nanosized Pb inclusions, was found to take place only in the peak region of the implantation profile where the Pb concentration was highest (∼ 4 at.%). TEM analysis of the as-implanted Si crystals showed that the Pb precipitates had sizes from about 2 to 20 nm and that they grew in parallel cube orientation relationship with the host matrix. The shape of the inclusions was found to be approximately cuboctahedral with poorly developed {111} and {100} facets. In-situ RBS/channelling heating/cooling experiments on both as-implanted samples and samples previously furnace-annealed at 1175 K showed a distinct melting/solidification hysteresis of the Pb inclusions around the bulk melting point for Pb at 600 K. These results were verified by in-situ TEM heating/cooling experiments on as-implanted samples.
Published Version
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